Merge pull request #3 from gilardh/master

paper librustzcash sync

.github/workflows/ci.yml

@@ -0,0 +1,120 @@
+name: CI checks
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: 1.37.0
+          override: true
+
+      # cargo fmt does not build the code, and running it in a fresh clone of
+      # the codebase will fail because the protobuf code has not been generated.
+      - name: cargo build
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --all
+
+      # Ensure all code has been formatted with rustfmt
+      - run: rustup component add rustfmt
+      - name: Check formatting
+        uses: actions-rs/cargo@v1
+        with:
+          command: fmt
+          args: --all -- --check --color always
+
+  test:
+    name: Test on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macOS-latest]
+
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: 1.37.0
+          override: true
+      - name: cargo fetch
+        uses: actions-rs/cargo@v1
+        with:
+          command: fetch
+      - name: Build tests
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --verbose --release --all --tests
+      - name: Run tests
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --verbose --release --all
+      - name: Run slow tests
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --verbose --release --all -- --ignored
+
+  codecov:
+    name: Code coverage
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v1
+      # Use stable for this to ensure that cargo-tarpaulin can be built.
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          override: true
+      - name: Install cargo-tarpaulin
+        uses: actions-rs/cargo@v1
+        with:
+          command: install
+          args: cargo-tarpaulin
+      - name: Generate coverage report
+        uses: actions-rs/cargo@v1
+        with:
+          command: tarpaulin
+          args: --release --timeout 600 --out Xml --packages "librustzcash,zcash_client_backend,zcash_primitives,zcash_proofs"
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v1.0.3
+        with:
+          token: ${{secrets.CODECOV_TOKEN}}
+
+  doc-links:
+    name: Nightly lint
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+      - name: cargo fetch
+        uses: actions-rs/cargo@v1
+        with:
+          command: fetch
+
+      # Ensure intra-documentation links all resolve correctly
+      # Requires #![deny(intra_doc_link_resolution_failure)] in crates.
+      - name: Check intra-doc links
+        uses: actions-rs/cargo@v1
+        with:
+          command: doc
+          args: --all --document-private-items
+
+      # Build benchmarks to prevent bitrot
+      - name: Build benchmarks
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --verbose --all --benches

.gitlab-ci.yml

@@ -0,0 +1,66 @@
+
+# /************************************************************************
+ #  File: .gitlab-ci.yml
+ #  Author: mdr0id
+ #  Date: 9/10/2018
+ #  Description:  Used to setup runners/jobs for librustzcash
+ #  Usage: Commit source and the pipeline will trigger the according jobs.
+ #         For now the build and test are done in the same jobs.
+ #
+ #  Known bugs/missing features:
+ #
+ # ************************************************************************/
+  
+stages:
+  - build
+  - test
+  - deploy
+
+rust-latest:
+  stage: build
+  image: rust:latest
+  script:
+    - cargo --verbose --version
+    - time cargo build --verbose
+
+rust-nightly:
+  stage: build
+  image: rustlang/rust:nightly
+  script:
+    - cargo --verbose --version
+    - cargo build --verbose
+  allow_failure: true
+
+librustzcash-test-latest:
+  stage: test
+  image: rust:latest
+  script:
+    - cargo --verbose --version
+    - time cargo test --release --verbose
+
+librustzcash-test-rust-nightly:
+  stage: test
+  image: rustlang/rust:nightly
+  script:
+    - cargo --verbose --version
+    - cargo test --release --verbose
+  allow_failure: true
+
+#used to manually deploy a given release
+librustzcash-rust-rc:
+  stage: deploy
+  image: rust:latest
+  script:
+    - cargo --verbose --version
+    - time cargo build --release --verbose
+  when: manual
+
+#used to manually deploy a given release
+librustzcash-rust-nightly-rc:
+  stage: deploy
+  image: rustlang/rust:nightly
+  script:
+    - cargo --verbose --version
+    - cargo build --release --verbose
+  allow_failure: true
+  when: manual

.travis.yml

@@ -0,0 +1,19 @@
+language: rust
+rust:
+  - 1.37.0
+
+cache: cargo
+
+before_script:
+  - rustup component add rustfmt
+
+script:
+  - cargo build --verbose --release --all
+  - cargo fmt --all -- --check
+  - cargo test --verbose --release --all
+  - cargo test --verbose --release --all -- --ignored
+
+before_cache:
+  - rm -rf "$TRAVIS_HOME/.cargo/registry/src"
+  - cargo install cargo-update || echo "cargo-update already installed"
+  - cargo install-update -a # update outdated cached binaries

Cargo.toml

@@ -1,37 +1,15 @@
-[package]
+[workspace]
-name = "librustzcash"
+members = [
-version = "0.1.0"
+    "bellman",
-authors = [
+    "ff",
-    "Sean Bowe <ewillbefull@gmail.com>",
+    "group",
-    "Jack Grigg <jack@z.cash>",
+    "librustzcash",
-    "Jay Graber <jay@z.cash>",
+    "pairing",
-    "Simon Liu <simon@z.cash>"
+    "zcash_client_backend",
-    ]
+    "zcash_history",
-
+    "zcash_primitives",
-[lib]
+    "zcash_proofs",
-name = "rustzcash"
+]
-path = "src/rustzcash.rs"
-crate-type = ["staticlib"]
-
-[dependencies]
-libc = "0.2"
-pairing = "0.14.2"
-lazy_static = "1"
-bellman = "0.1"
-byteorder = "1"
-rand = "0.4"
-
-[dependencies.blake2-rfc]
-git = "https://github.com/gtank/blake2-rfc"
-rev = "7a5b5fc99ae483a0043db7547fb79a6fa44b88a9"
-
-[dependencies.sapling-crypto]
-git = "https://github.com/zcash-hackworks/sapling-crypto"
-rev = "21084bde2019c04bd34208e63c3560fe2c02fb0e"
-
-[dependencies.zip32]
-git = "https://github.com/zcash-hackworks/zip32"
-rev = "176470ef41583b5bd0bd749bd1b61d417aa8ec79"
 
 [profile.release]
 lto = true

LICENSE-MIT

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2017 Zcash Company
+Copyright (c) 2017-2019 Electric Coin Company
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,10 +1,15 @@
-# librustzcash
+# Zcash Rust crates
 
-This repository contains librustzcash, a static library for Zcash code assets written in Rust.
+This repository contains a (work-in-progress) set of Rust crates for
+working with Zcash.
+
+## Security Warnings
+
+These libraries are currently under development and have not been fully-reviewed.
 
 ## License
 
-Licensed under either of
+All code in this workspace is licensed under either of
 
  * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
@@ -17,4 +22,3 @@ Unless you explicitly state otherwise, any contribution intentionally
 submitted for inclusion in the work by you, as defined in the Apache-2.0
 license, shall be dual licensed as above, without any additional terms or
 conditions.
-

bellman/.gitignore

@@ -0,0 +1,2 @@
+target
+Cargo.lock

bellman/COPYRIGHT

@@ -0,0 +1,14 @@
+Copyrights in the "bellman" library are retained by their contributors. No
+copyright assignment is required to contribute to the "bellman" library.
+
+The "bellman" library is licensed under either of
+
+ * Apache License, Version 2.0, (see ./LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license (see ./LICENSE-MIT or http://opensource.org/licenses/MIT)
+
+at your option.
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

bellman/Cargo.toml

@@ -0,0 +1,42 @@
+[package]
+authors = ["Sean Bowe <ewillbefull@gmail.com>"]
+description = "zk-SNARK library"
+readme = "README.md"
+homepage = "https://github.com/ebfull/bellman"
+license = "MIT/Apache-2.0"
+name = "bellman"
+repository = "https://github.com/ebfull/bellman"
+version = "0.2.0"
+edition = "2018"
+
+[dependencies]
+bit-vec = "0.4.4"
+blake2s_simd = "0.5"
+ff = { version = "0.5.0", path = "../ff" }
+futures = "0.1"
+futures-cpupool = { version = "0.1", optional = true }
+group = { version = "0.2.0", path = "../group" }
+num_cpus = { version = "1", optional = true }
+crossbeam = { version = "0.7", optional = true }
+pairing = { version = "0.15.0", path = "../pairing", optional = true }
+rand_core = "0.5"
+byteorder = "1"
+
+[dev-dependencies]
+hex-literal = "0.2"
+rand = "0.7"
+rand_xorshift = "0.2"
+sha2 = "0.8"
+
+[features]
+groth16 = ["pairing"]
+multicore = ["futures-cpupool", "crossbeam", "num_cpus"]
+default = ["groth16", "multicore"]
+
+[[test]]
+name = "mimc"
+path = "tests/mimc.rs"
+required-features = ["groth16"]
+
+[badges]
+maintenance = { status = "actively-developed" }

bellman/LICENSE-APACHE

@@ -0,0 +1,201 @@
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+
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bellman/LICENSE-MIT

@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
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+
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+
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+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

bellman/README.md

@@ -0,0 +1,30 @@
+# bellman [![Crates.io](https://img.shields.io/crates/v/bellman.svg)](https://crates.io/crates/bellman) #
+
+`bellman` is a crate for building zk-SNARK circuits. It provides circuit traits
+and primitive structures, as well as basic gadget implementations such as
+booleans and number abstractions.
+
+## Roadmap
+
+`bellman` is being refactored into a generic proving library. Currently it is
+pairing-specific, and different types of proving systems need to be implemented
+as sub-modules. After the refactor, `bellman` will be generic using the `ff` and
+`group` crates, while specific proving systems will be separate crates that pull
+in the dependencies they require.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

bellman/src/domain.rs

@@ -0,0 +1,503 @@
+//! This module contains an [`EvaluationDomain`] abstraction for performing
+//! various kinds of polynomial arithmetic on top of the scalar field.
+//!
+//! In pairing-based SNARKs like [Groth16], we need to calculate a quotient
+//! polynomial over a target polynomial with roots at distinct points associated
+//! with each constraint of the constraint system. In order to be efficient, we
+//! choose these roots to be the powers of a 2<sup>n</sup> root of unity in the
+//! field. This allows us to perform polynomial operations in O(n) by performing
+//! an O(n log n) FFT over such a domain.
+//!
+//! [`EvaluationDomain`]: crate::domain::EvaluationDomain
+//! [Groth16]: https://eprint.iacr.org/2016/260
+
+use ff::{Field, PrimeField, ScalarEngine};
+use group::CurveProjective;
+
+use super::SynthesisError;
+
+use super::multicore::Worker;
+
+pub struct EvaluationDomain<E: ScalarEngine, G: Group<E>> {
+    coeffs: Vec<G>,
+    exp: u32,
+    omega: E::Fr,
+    omegainv: E::Fr,
+    geninv: E::Fr,
+    minv: E::Fr,
+}
+
+impl<E: ScalarEngine, G: Group<E>> AsRef<[G]> for EvaluationDomain<E, G> {
+    fn as_ref(&self) -> &[G] {
+        &self.coeffs
+    }
+}
+
+impl<E: ScalarEngine, G: Group<E>> AsMut<[G]> for EvaluationDomain<E, G> {
+    fn as_mut(&mut self) -> &mut [G] {
+        &mut self.coeffs
+    }
+}
+
+impl<E: ScalarEngine, G: Group<E>> EvaluationDomain<E, G> {
+    pub fn into_coeffs(self) -> Vec<G> {
+        self.coeffs
+    }
+
+    pub fn from_coeffs(mut coeffs: Vec<G>) -> Result<EvaluationDomain<E, G>, SynthesisError> {
+        // Compute the size of our evaluation domain
+        let mut m = 1;
+        let mut exp = 0;
+        while m < coeffs.len() {
+            m *= 2;
+            exp += 1;
+
+            // The pairing-friendly curve may not be able to support
+            // large enough (radix2) evaluation domains.
+            if exp >= E::Fr::S {
+                return Err(SynthesisError::PolynomialDegreeTooLarge);
+            }
+        }
+
+        // Compute omega, the 2^exp primitive root of unity
+        let mut omega = E::Fr::root_of_unity();
+        for _ in exp..E::Fr::S {
+            omega.square();
+        }
+
+        // Extend the coeffs vector with zeroes if necessary
+        coeffs.resize(m, G::group_zero());
+
+        Ok(EvaluationDomain {
+            coeffs,
+            exp,
+            omega,
+            omegainv: omega.inverse().unwrap(),
+            geninv: E::Fr::multiplicative_generator().inverse().unwrap(),
+            minv: E::Fr::from_str(&format!("{}", m))
+                .unwrap()
+                .inverse()
+                .unwrap(),
+        })
+    }
+
+    pub fn fft(&mut self, worker: &Worker) {
+        best_fft(&mut self.coeffs, worker, &self.omega, self.exp);
+    }
+
+    pub fn ifft(&mut self, worker: &Worker) {
+        best_fft(&mut self.coeffs, worker, &self.omegainv, self.exp);
+
+        worker.scope(self.coeffs.len(), |scope, chunk| {
+            let minv = self.minv;
+
+            for v in self.coeffs.chunks_mut(chunk) {
+                scope.spawn(move |_scope| {
+                    for v in v {
+                        v.group_mul_assign(&minv);
+                    }
+                });
+            }
+        });
+    }
+
+    pub fn distribute_powers(&mut self, worker: &Worker, g: E::Fr) {
+        worker.scope(self.coeffs.len(), |scope, chunk| {
+            for (i, v) in self.coeffs.chunks_mut(chunk).enumerate() {
+                scope.spawn(move |_scope| {
+                    let mut u = g.pow(&[(i * chunk) as u64]);
+                    for v in v.iter_mut() {
+                        v.group_mul_assign(&u);
+                        u.mul_assign(&g);
+                    }
+                });
+            }
+        });
+    }
+
+    pub fn coset_fft(&mut self, worker: &Worker) {
+        self.distribute_powers(worker, E::Fr::multiplicative_generator());
+        self.fft(worker);
+    }
+
+    pub fn icoset_fft(&mut self, worker: &Worker) {
+        let geninv = self.geninv;
+
+        self.ifft(worker);
+        self.distribute_powers(worker, geninv);
+    }
+
+    /// This evaluates t(tau) for this domain, which is
+    /// tau^m - 1 for these radix-2 domains.
+    pub fn z(&self, tau: &E::Fr) -> E::Fr {
+        let mut tmp = tau.pow(&[self.coeffs.len() as u64]);
+        tmp.sub_assign(&E::Fr::one());
+
+        tmp
+    }
+
+    /// The target polynomial is the zero polynomial in our
+    /// evaluation domain, so we must perform division over
+    /// a coset.
+    pub fn divide_by_z_on_coset(&mut self, worker: &Worker) {
+        let i = self
+            .z(&E::Fr::multiplicative_generator())
+            .inverse()
+            .unwrap();
+
+        worker.scope(self.coeffs.len(), |scope, chunk| {
+            for v in self.coeffs.chunks_mut(chunk) {
+                scope.spawn(move |_scope| {
+                    for v in v {
+                        v.group_mul_assign(&i);
+                    }
+                });
+            }
+        });
+    }
+
+    /// Perform O(n) multiplication of two polynomials in the domain.
+    pub fn mul_assign(&mut self, worker: &Worker, other: &EvaluationDomain<E, Scalar<E>>) {
+        assert_eq!(self.coeffs.len(), other.coeffs.len());
+
+        worker.scope(self.coeffs.len(), |scope, chunk| {
+            for (a, b) in self
+                .coeffs
+                .chunks_mut(chunk)
+                .zip(other.coeffs.chunks(chunk))
+            {
+                scope.spawn(move |_scope| {
+                    for (a, b) in a.iter_mut().zip(b.iter()) {
+                        a.group_mul_assign(&b.0);
+                    }
+                });
+            }
+        });
+    }
+
+    /// Perform O(n) subtraction of one polynomial from another in the domain.
+    pub fn sub_assign(&mut self, worker: &Worker, other: &EvaluationDomain<E, G>) {
+        assert_eq!(self.coeffs.len(), other.coeffs.len());
+
+        worker.scope(self.coeffs.len(), |scope, chunk| {
+            for (a, b) in self
+                .coeffs
+                .chunks_mut(chunk)
+                .zip(other.coeffs.chunks(chunk))
+            {
+                scope.spawn(move |_scope| {
+                    for (a, b) in a.iter_mut().zip(b.iter()) {
+                        a.group_sub_assign(&b);
+                    }
+                });
+            }
+        });
+    }
+}
+
+pub trait Group<E: ScalarEngine>: Sized + Copy + Clone + Send + Sync {
+    fn group_zero() -> Self;
+    fn group_mul_assign(&mut self, by: &E::Fr);
+    fn group_add_assign(&mut self, other: &Self);
+    fn group_sub_assign(&mut self, other: &Self);
+}
+
+pub struct Point<G: CurveProjective>(pub G);
+
+impl<G: CurveProjective> PartialEq for Point<G> {
+    fn eq(&self, other: &Point<G>) -> bool {
+        self.0 == other.0
+    }
+}
+
+impl<G: CurveProjective> Copy for Point<G> {}
+
+impl<G: CurveProjective> Clone for Point<G> {
+    fn clone(&self) -> Point<G> {
+        *self
+    }
+}
+
+impl<G: CurveProjective> Group<G::Engine> for Point<G> {
+    fn group_zero() -> Self {
+        Point(G::zero())
+    }
+    fn group_mul_assign(&mut self, by: &G::Scalar) {
+        self.0.mul_assign(by.into_repr());
+    }
+    fn group_add_assign(&mut self, other: &Self) {
+        self.0.add_assign(&other.0);
+    }
+    fn group_sub_assign(&mut self, other: &Self) {
+        self.0.sub_assign(&other.0);
+    }
+}
+
+pub struct Scalar<E: ScalarEngine>(pub E::Fr);
+
+impl<E: ScalarEngine> PartialEq for Scalar<E> {
+    fn eq(&self, other: &Scalar<E>) -> bool {
+        self.0 == other.0
+    }
+}
+
+impl<E: ScalarEngine> Copy for Scalar<E> {}
+
+impl<E: ScalarEngine> Clone for Scalar<E> {
+    fn clone(&self) -> Scalar<E> {
+        *self
+    }
+}
+
+impl<E: ScalarEngine> Group<E> for Scalar<E> {
+    fn group_zero() -> Self {
+        Scalar(E::Fr::zero())
+    }
+    fn group_mul_assign(&mut self, by: &E::Fr) {
+        self.0.mul_assign(by);
+    }
+    fn group_add_assign(&mut self, other: &Self) {
+        self.0.add_assign(&other.0);
+    }
+    fn group_sub_assign(&mut self, other: &Self) {
+        self.0.sub_assign(&other.0);
+    }
+}
+
+fn best_fft<E: ScalarEngine, T: Group<E>>(a: &mut [T], worker: &Worker, omega: &E::Fr, log_n: u32) {
+    let log_cpus = worker.log_num_cpus();
+
+    if log_n <= log_cpus {
+        serial_fft(a, omega, log_n);
+    } else {
+        parallel_fft(a, worker, omega, log_n, log_cpus);
+    }
+}
+
+fn serial_fft<E: ScalarEngine, T: Group<E>>(a: &mut [T], omega: &E::Fr, log_n: u32) {
+    fn bitreverse(mut n: u32, l: u32) -> u32 {
+        let mut r = 0;
+        for _ in 0..l {
+            r = (r << 1) | (n & 1);
+            n >>= 1;
+        }
+        r
+    }
+
+    let n = a.len() as u32;
+    assert_eq!(n, 1 << log_n);
+
+    for k in 0..n {
+        let rk = bitreverse(k, log_n);
+        if k < rk {
+            a.swap(rk as usize, k as usize);
+        }
+    }
+
+    let mut m = 1;
+    for _ in 0..log_n {
+        let w_m = omega.pow(&[u64::from(n / (2 * m))]);
+
+        let mut k = 0;
+        while k < n {
+            let mut w = E::Fr::one();
+            for j in 0..m {
+                let mut t = a[(k + j + m) as usize];
+                t.group_mul_assign(&w);
+                let mut tmp = a[(k + j) as usize];
+                tmp.group_sub_assign(&t);
+                a[(k + j + m) as usize] = tmp;
+                a[(k + j) as usize].group_add_assign(&t);
+                w.mul_assign(&w_m);
+            }
+
+            k += 2 * m;
+        }
+
+        m *= 2;
+    }
+}
+
+fn parallel_fft<E: ScalarEngine, T: Group<E>>(
+    a: &mut [T],
+    worker: &Worker,
+    omega: &E::Fr,
+    log_n: u32,
+    log_cpus: u32,
+) {
+    assert!(log_n >= log_cpus);
+
+    let num_cpus = 1 << log_cpus;
+    let log_new_n = log_n - log_cpus;
+    let mut tmp = vec![vec![T::group_zero(); 1 << log_new_n]; num_cpus];
+    let new_omega = omega.pow(&[num_cpus as u64]);
+
+    worker.scope(0, |scope, _| {
+        let a = &*a;
+
+        for (j, tmp) in tmp.iter_mut().enumerate() {
+            scope.spawn(move |_scope| {
+                // Shuffle into a sub-FFT
+                let omega_j = omega.pow(&[j as u64]);
+                let omega_step = omega.pow(&[(j as u64) << log_new_n]);
+
+                let mut elt = E::Fr::one();
+                for (i, tmp) in tmp.iter_mut().enumerate() {
+                    for s in 0..num_cpus {
+                        let idx = (i + (s << log_new_n)) % (1 << log_n);
+                        let mut t = a[idx];
+                        t.group_mul_assign(&elt);
+                        tmp.group_add_assign(&t);
+                        elt.mul_assign(&omega_step);
+                    }
+                    elt.mul_assign(&omega_j);
+                }
+
+                // Perform sub-FFT
+                serial_fft(tmp, &new_omega, log_new_n);
+            });
+        }
+    });
+
+    // TODO: does this hurt or help?
+    worker.scope(a.len(), |scope, chunk| {
+        let tmp = &tmp;
+
+        for (idx, a) in a.chunks_mut(chunk).enumerate() {
+            scope.spawn(move |_scope| {
+                let mut idx = idx * chunk;
+                let mask = (1 << log_cpus) - 1;
+                for a in a {
+                    *a = tmp[idx & mask][idx >> log_cpus];
+                    idx += 1;
+                }
+            });
+        }
+    });
+}
+
+// Test multiplying various (low degree) polynomials together and
+// comparing with naive evaluations.
+#[cfg(feature = "pairing")]
+#[test]
+fn polynomial_arith() {
+    use pairing::bls12_381::Bls12;
+    use rand_core::RngCore;
+
+    fn test_mul<E: ScalarEngine, R: RngCore>(rng: &mut R) {
+        let worker = Worker::new();
+
+        for coeffs_a in 0..70 {
+            for coeffs_b in 0..70 {
+                let mut a: Vec<_> = (0..coeffs_a)
+                    .map(|_| Scalar::<E>(E::Fr::random(rng)))
+                    .collect();
+                let mut b: Vec<_> = (0..coeffs_b)
+                    .map(|_| Scalar::<E>(E::Fr::random(rng)))
+                    .collect();
+
+                // naive evaluation
+                let mut naive = vec![Scalar(E::Fr::zero()); coeffs_a + coeffs_b];
+                for (i1, a) in a.iter().enumerate() {
+                    for (i2, b) in b.iter().enumerate() {
+                        let mut prod = *a;
+                        prod.group_mul_assign(&b.0);
+                        naive[i1 + i2].group_add_assign(&prod);
+                    }
+                }
+
+                a.resize(coeffs_a + coeffs_b, Scalar(E::Fr::zero()));
+                b.resize(coeffs_a + coeffs_b, Scalar(E::Fr::zero()));
+
+                let mut a = EvaluationDomain::from_coeffs(a).unwrap();
+                let mut b = EvaluationDomain::from_coeffs(b).unwrap();
+
+                a.fft(&worker);
+                b.fft(&worker);
+                a.mul_assign(&worker, &b);
+                a.ifft(&worker);
+
+                for (naive, fft) in naive.iter().zip(a.coeffs.iter()) {
+                    assert!(naive == fft);
+                }
+            }
+        }
+    }
+
+    let rng = &mut rand::thread_rng();
+
+    test_mul::<Bls12, _>(rng);
+}
+
+#[cfg(feature = "pairing")]
+#[test]
+fn fft_composition() {
+    use pairing::bls12_381::Bls12;
+    use rand_core::RngCore;
+
+    fn test_comp<E: ScalarEngine, R: RngCore>(rng: &mut R) {
+        let worker = Worker::new();
+
+        for coeffs in 0..10 {
+            let coeffs = 1 << coeffs;
+
+            let mut v = vec![];
+            for _ in 0..coeffs {
+                v.push(Scalar::<E>(E::Fr::random(rng)));
+            }
+
+            let mut domain = EvaluationDomain::from_coeffs(v.clone()).unwrap();
+            domain.ifft(&worker);
+            domain.fft(&worker);
+            assert!(v == domain.coeffs);
+            domain.fft(&worker);
+            domain.ifft(&worker);
+            assert!(v == domain.coeffs);
+            domain.icoset_fft(&worker);
+            domain.coset_fft(&worker);
+            assert!(v == domain.coeffs);
+            domain.coset_fft(&worker);
+            domain.icoset_fft(&worker);
+            assert!(v == domain.coeffs);
+        }
+    }
+
+    let rng = &mut rand::thread_rng();
+
+    test_comp::<Bls12, _>(rng);
+}
+
+#[cfg(feature = "pairing")]
+#[test]
+fn parallel_fft_consistency() {
+    use pairing::bls12_381::Bls12;
+    use rand_core::RngCore;
+    use std::cmp::min;
+
+    fn test_consistency<E: ScalarEngine, R: RngCore>(rng: &mut R) {
+        let worker = Worker::new();
+
+        for _ in 0..5 {
+            for log_d in 0..10 {
+                let d = 1 << log_d;
+
+                let v1 = (0..d)
+                    .map(|_| Scalar::<E>(E::Fr::random(rng)))
+                    .collect::<Vec<_>>();
+                let mut v1 = EvaluationDomain::from_coeffs(v1).unwrap();
+                let mut v2 = EvaluationDomain::from_coeffs(v1.coeffs.clone()).unwrap();
+
+                for log_cpus in log_d..min(log_d + 1, 3) {
+                    parallel_fft(&mut v1.coeffs, &worker, &v1.omega, log_d, log_cpus);
+                    serial_fft(&mut v2.coeffs, &v2.omega, log_d);
+
+                    assert!(v1.coeffs == v2.coeffs);
+                }
+            }
+        }
+    }
+
+    let rng = &mut rand::thread_rng();
+
+    test_consistency::<Bls12, _>(rng);
+}

bellman/src/gadgets.rs

@@ -0,0 +1,33 @@
+//! Self-contained sub-circuit implementations for various primitives.
+
+pub mod test;
+
+pub mod blake2s;
+pub mod boolean;
+pub mod lookup;
+pub mod multieq;
+pub mod multipack;
+pub mod num;
+pub mod sha256;
+pub mod uint32;
+
+use crate::SynthesisError;
+
+// TODO: This should probably be removed and we
+// should use existing helper methods on `Option`
+// for mapping with an error.
+/// This basically is just an extension to `Option`
+/// which allows for a convenient mapping to an
+/// error on `None`.
+pub trait Assignment<T> {
+    fn get(&self) -> Result<&T, SynthesisError>;
+}
+
+impl<T> Assignment<T> for Option<T> {
+    fn get(&self) -> Result<&T, SynthesisError> {
+        match *self {
+            Some(ref v) => Ok(v),
+            None => Err(SynthesisError::AssignmentMissing),
+        }
+    }
+}

bellman/src/gadgets/blake2s.rs

@@ -0,0 +1,697 @@
+//! The [BLAKE2s] hash function with personalization support.
+//!
+//! [BLAKE2s]: https://tools.ietf.org/html/rfc7693
+
+use super::{boolean::Boolean, multieq::MultiEq, uint32::UInt32};
+use crate::{ConstraintSystem, SynthesisError};
+use ff::ScalarEngine;
+
+/*
+2.1.  Parameters
+   The following table summarizes various parameters and their ranges:
+                            | BLAKE2b          | BLAKE2s          |
+              --------------+------------------+------------------+
+               Bits in word | w = 64           | w = 32           |
+               Rounds in F  | r = 12           | r = 10           |
+               Block bytes  | bb = 128         | bb = 64          |
+               Hash bytes   | 1 <= nn <= 64    | 1 <= nn <= 32    |
+               Key bytes    | 0 <= kk <= 64    | 0 <= kk <= 32    |
+               Input bytes  | 0 <= ll < 2**128 | 0 <= ll < 2**64  |
+              --------------+------------------+------------------+
+               G Rotation   | (R1, R2, R3, R4) | (R1, R2, R3, R4) |
+                constants = | (32, 24, 16, 63) | (16, 12,  8,  7) |
+              --------------+------------------+------------------+
+*/
+
+const R1: usize = 16;
+const R2: usize = 12;
+const R3: usize = 8;
+const R4: usize = 7;
+
+/*
+          Round   |  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 |
+        ----------+-------------------------------------------------+
+         SIGMA[0] |  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 |
+         SIGMA[1] | 14 10  4  8  9 15 13  6  1 12  0  2 11  7  5  3 |
+         SIGMA[2] | 11  8 12  0  5  2 15 13 10 14  3  6  7  1  9  4 |
+         SIGMA[3] |  7  9  3  1 13 12 11 14  2  6  5 10  4  0 15  8 |
+         SIGMA[4] |  9  0  5  7  2  4 10 15 14  1 11 12  6  8  3 13 |
+         SIGMA[5] |  2 12  6 10  0 11  8  3  4 13  7  5 15 14  1  9 |
+         SIGMA[6] | 12  5  1 15 14 13  4 10  0  7  6  3  9  2  8 11 |
+         SIGMA[7] | 13 11  7 14 12  1  3  9  5  0 15  4  8  6  2 10 |
+         SIGMA[8] |  6 15 14  9 11  3  0  8 12  2 13  7  1  4 10  5 |
+         SIGMA[9] | 10  2  8  4  7  6  1  5 15 11  9 14  3 12 13  0 |
+        ----------+-------------------------------------------------+
+*/
+
+const SIGMA: [[usize; 16]; 10] = [
+    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+    [14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3],
+    [11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4],
+    [7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8],
+    [9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13],
+    [2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9],
+    [12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11],
+    [13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10],
+    [6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5],
+    [10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0],
+];
+
+/*
+3.1.  Mixing Function G
+   The G primitive function mixes two input words, "x" and "y", into
+   four words indexed by "a", "b", "c", and "d" in the working vector
+   v[0..15].  The full modified vector is returned.  The rotation
+   constants (R1, R2, R3, R4) are given in Section 2.1.
+       FUNCTION G( v[0..15], a, b, c, d, x, y )
+       |
+       |   v[a] := (v[a] + v[b] + x) mod 2**w
+       |   v[d] := (v[d] ^ v[a]) >>> R1
+       |   v[c] := (v[c] + v[d])     mod 2**w
+       |   v[b] := (v[b] ^ v[c]) >>> R2
+       |   v[a] := (v[a] + v[b] + y) mod 2**w
+       |   v[d] := (v[d] ^ v[a]) >>> R3
+       |   v[c] := (v[c] + v[d])     mod 2**w
+       |   v[b] := (v[b] ^ v[c]) >>> R4
+       |
+       |   RETURN v[0..15]
+       |
+       END FUNCTION.
+*/
+
+fn mixing_g<E: ScalarEngine, CS: ConstraintSystem<E>, M>(
+    mut cs: M,
+    v: &mut [UInt32],
+    a: usize,
+    b: usize,
+    c: usize,
+    d: usize,
+    x: &UInt32,
+    y: &UInt32,
+) -> Result<(), SynthesisError>
+where
+    M: ConstraintSystem<E, Root = MultiEq<E, CS>>,
+{
+    v[a] = UInt32::addmany(
+        cs.namespace(|| "mixing step 1"),
+        &[v[a].clone(), v[b].clone(), x.clone()],
+    )?;
+    v[d] = v[d].xor(cs.namespace(|| "mixing step 2"), &v[a])?.rotr(R1);
+    v[c] = UInt32::addmany(
+        cs.namespace(|| "mixing step 3"),
+        &[v[c].clone(), v[d].clone()],
+    )?;
+    v[b] = v[b].xor(cs.namespace(|| "mixing step 4"), &v[c])?.rotr(R2);
+    v[a] = UInt32::addmany(
+        cs.namespace(|| "mixing step 5"),
+        &[v[a].clone(), v[b].clone(), y.clone()],
+    )?;
+    v[d] = v[d].xor(cs.namespace(|| "mixing step 6"), &v[a])?.rotr(R3);
+    v[c] = UInt32::addmany(
+        cs.namespace(|| "mixing step 7"),
+        &[v[c].clone(), v[d].clone()],
+    )?;
+    v[b] = v[b].xor(cs.namespace(|| "mixing step 8"), &v[c])?.rotr(R4);
+
+    Ok(())
+}
+
+/*
+3.2.  Compression Function F
+   Compression function F takes as an argument the state vector "h",
+   message block vector "m" (last block is padded with zeros to full
+   block size, if required), 2w-bit offset counter "t", and final block
+   indicator flag "f".  Local vector v[0..15] is used in processing.  F
+   returns a new state vector.  The number of rounds, "r", is 12 for
+   BLAKE2b and 10 for BLAKE2s.  Rounds are numbered from 0 to r - 1.
+       FUNCTION F( h[0..7], m[0..15], t, f )
+       |
+       |      // Initialize local work vector v[0..15]
+       |      v[0..7] := h[0..7]              // First half from state.
+       |      v[8..15] := IV[0..7]            // Second half from IV.
+       |
+       |      v[12] := v[12] ^ (t mod 2**w)   // Low word of the offset.
+       |      v[13] := v[13] ^ (t >> w)       // High word.
+       |
+       |      IF f = TRUE THEN                // last block flag?
+       |      |   v[14] := v[14] ^ 0xFF..FF   // Invert all bits.
+       |      END IF.
+       |
+       |      // Cryptographic mixing
+       |      FOR i = 0 TO r - 1 DO           // Ten or twelve rounds.
+       |      |
+       |      |   // Message word selection permutation for this round.
+       |      |   s[0..15] := SIGMA[i mod 10][0..15]
+       |      |
+       |      |   v := G( v, 0, 4,  8, 12, m[s[ 0]], m[s[ 1]] )
+       |      |   v := G( v, 1, 5,  9, 13, m[s[ 2]], m[s[ 3]] )
+       |      |   v := G( v, 2, 6, 10, 14, m[s[ 4]], m[s[ 5]] )
+       |      |   v := G( v, 3, 7, 11, 15, m[s[ 6]], m[s[ 7]] )
+       |      |
+       |      |   v := G( v, 0, 5, 10, 15, m[s[ 8]], m[s[ 9]] )
+       |      |   v := G( v, 1, 6, 11, 12, m[s[10]], m[s[11]] )
+       |      |   v := G( v, 2, 7,  8, 13, m[s[12]], m[s[13]] )
+       |      |   v := G( v, 3, 4,  9, 14, m[s[14]], m[s[15]] )
+       |      |
+       |      END FOR
+       |
+       |      FOR i = 0 TO 7 DO               // XOR the two halves.
+       |      |   h[i] := h[i] ^ v[i] ^ v[i + 8]
+       |      END FOR.
+       |
+       |      RETURN h[0..7]                  // New state.
+       |
+       END FUNCTION.
+*/
+
+fn blake2s_compression<E: ScalarEngine, CS: ConstraintSystem<E>>(
+    mut cs: CS,
+    h: &mut [UInt32],
+    m: &[UInt32],
+    t: u64,
+    f: bool,
+) -> Result<(), SynthesisError> {
+    assert_eq!(h.len(), 8);
+    assert_eq!(m.len(), 16);
+
+    /*
+    static const uint32_t blake2s_iv[8] =
+    {
+        0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A,
+        0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19
+    };
+    */
+
+    let mut v = Vec::with_capacity(16);
+    v.extend_from_slice(h);
+    v.push(UInt32::constant(0x6A09E667));
+    v.push(UInt32::constant(0xBB67AE85));
+    v.push(UInt32::constant(0x3C6EF372));
+    v.push(UInt32::constant(0xA54FF53A));
+    v.push(UInt32::constant(0x510E527F));
+    v.push(UInt32::constant(0x9B05688C));
+    v.push(UInt32::constant(0x1F83D9AB));
+    v.push(UInt32::constant(0x5BE0CD19));
+
+    assert_eq!(v.len(), 16);
+
+    v[12] = v[12].xor(cs.namespace(|| "first xor"), &UInt32::constant(t as u32))?;
+    v[13] = v[13].xor(
+        cs.namespace(|| "second xor"),
+        &UInt32::constant((t >> 32) as u32),
+    )?;
+
+    if f {
+        v[14] = v[14].xor(
+            cs.namespace(|| "third xor"),
+            &UInt32::constant(u32::max_value()),
+        )?;
+    }
+
+    {
+        let mut cs = MultiEq::new(&mut cs);
+
+        for i in 0..10 {
+            let mut cs = cs.namespace(|| format!("round {}", i));
+
+            let s = SIGMA[i % 10];
+
+            mixing_g(
+                cs.namespace(|| "mixing invocation 1"),
+                &mut v,
+                0,
+                4,
+                8,
+                12,
+                &m[s[0]],
+                &m[s[1]],
+            )?;
+            mixing_g(
+                cs.namespace(|| "mixing invocation 2"),
+                &mut v,
+                1,
+                5,
+                9,
+                13,
+                &m[s[2]],
+                &m[s[3]],
+            )?;
+            mixing_g(
+                cs.namespace(|| "mixing invocation 3"),
+                &mut v,
+                2,
+                6,
+                10,
+                14,
+                &m[s[4]],
+                &m[s[5]],
+            )?;
+            mixing_g(
+                cs.namespace(|| "mixing invocation 4"),
+                &mut v,
+                3,
+                7,
+                11,
+                15,
+                &m[s[6]],
+                &m[s[7]],
+            )?;
+
+            mixing_g(
+                cs.namespace(|| "mixing invocation 5"),
+                &mut v,
+                0,
+                5,
+                10,
+                15,
+                &m[s[8]],
+                &m[s[9]],
+            )?;
+            mixing_g(
+                cs.namespace(|| "mixing invocation 6"),
+                &mut v,
+                1,
+                6,
+                11,
+                12,
+                &m[s[10]],
+                &m[s[11]],
+            )?;
+            mixing_g(
+                cs.namespace(|| "mixing invocation 7"),
+                &mut v,
+                2,
+                7,
+                8,
+                13,
+                &m[s[12]],
+                &m[s[13]],
+            )?;
+            mixing_g(
+                cs.namespace(|| "mixing invocation 8"),
+                &mut v,
+                3,
+                4,
+                9,
+                14,
+                &m[s[14]],
+                &m[s[15]],
+            )?;
+        }
+    }
+
+    for i in 0..8 {
+        let mut cs = cs.namespace(|| format!("h[{i}] ^ v[{i}] ^ v[{i} + 8]", i = i));
+
+        h[i] = h[i].xor(cs.namespace(|| "first xor"), &v[i])?;
+        h[i] = h[i].xor(cs.namespace(|| "second xor"), &v[i + 8])?;
+    }
+
+    Ok(())
+}
+
+/*
+        FUNCTION BLAKE2( d[0..dd-1], ll, kk, nn )
+        |
+        |     h[0..7] := IV[0..7]          // Initialization Vector.
+        |
+        |     // Parameter block p[0]
+        |     h[0] := h[0] ^ 0x01010000 ^ (kk << 8) ^ nn
+        |
+        |     // Process padded key and data blocks
+        |     IF dd > 1 THEN
+        |     |       FOR i = 0 TO dd - 2 DO
+        |     |       |       h := F( h, d[i], (i + 1) * bb, FALSE )
+        |     |       END FOR.
+        |     END IF.
+        |
+        |     // Final block.
+        |     IF kk = 0 THEN
+        |     |       h := F( h, d[dd - 1], ll, TRUE )
+        |     ELSE
+        |     |       h := F( h, d[dd - 1], ll + bb, TRUE )
+        |     END IF.
+        |
+        |     RETURN first "nn" bytes from little-endian word array h[].
+        |
+        END FUNCTION.
+*/
+
+pub fn blake2s<E: ScalarEngine, CS: ConstraintSystem<E>>(
+    mut cs: CS,
+    input: &[Boolean],
+    personalization: &[u8],
+) -> Result<Vec<Boolean>, SynthesisError> {
+    use byteorder::{ByteOrder, LittleEndian};
+
+    assert_eq!(personalization.len(), 8);
+    assert!(input.len() % 8 == 0);
+
+    let mut h = Vec::with_capacity(8);
+    h.push(UInt32::constant(0x6A09E667 ^ 0x01010000 ^ 32));
+    h.push(UInt32::constant(0xBB67AE85));
+    h.push(UInt32::constant(0x3C6EF372));
+    h.push(UInt32::constant(0xA54FF53A));
+    h.push(UInt32::constant(0x510E527F));
+    h.push(UInt32::constant(0x9B05688C));
+
+    // Personalization is stored here
+    h.push(UInt32::constant(
+        0x1F83D9AB ^ LittleEndian::read_u32(&personalization[0..4]),
+    ));
+    h.push(UInt32::constant(
+        0x5BE0CD19 ^ LittleEndian::read_u32(&personalization[4..8]),
+    ));
+
+    let mut blocks: Vec<Vec<UInt32>> = vec![];
+
+    for block in input.chunks(512) {
+        let mut this_block = Vec::with_capacity(16);
+        for word in block.chunks(32) {
+            let mut tmp = word.to_vec();
+            while tmp.len() < 32 {
+                tmp.push(Boolean::constant(false));
+            }
+            this_block.push(UInt32::from_bits(&tmp));
+        }
+        while this_block.len() < 16 {
+            this_block.push(UInt32::constant(0));
+        }
+        blocks.push(this_block);
+    }
+
+    if blocks.is_empty() {
+        blocks.push((0..16).map(|_| UInt32::constant(0)).collect());
+    }
+
+    for (i, block) in blocks[0..blocks.len() - 1].iter().enumerate() {
+        let cs = cs.namespace(|| format!("block {}", i));
+
+        blake2s_compression(cs, &mut h, block, ((i as u64) + 1) * 64, false)?;
+    }
+
+    {
+        let cs = cs.namespace(|| "final block");
+
+        blake2s_compression(
+            cs,
+            &mut h,
+            &blocks[blocks.len() - 1],
+            (input.len() / 8) as u64,
+            true,
+        )?;
+    }
+
+    Ok(h.into_iter().flat_map(|b| b.into_bits()).collect())
+}
+
+#[cfg(test)]
+mod test {
+    use blake2s_simd::Params as Blake2sParams;
+    use hex_literal::hex;
+    use pairing::bls12_381::Bls12;
+    use rand_core::{RngCore, SeedableRng};
+    use rand_xorshift::XorShiftRng;
+
+    use super::blake2s;
+    use crate::gadgets::boolean::{AllocatedBit, Boolean};
+    use crate::gadgets::test::TestConstraintSystem;
+    use crate::ConstraintSystem;
+
+    #[test]
+    fn test_blank_hash() {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+        let input_bits = vec![];
+        let out = blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+        assert!(cs.is_satisfied());
+        assert_eq!(cs.num_constraints(), 0);
+
+        // >>> import blake2s from hashlib
+        // >>> h = blake2s(digest_size=32, person=b'12345678')
+        // >>> h.hexdigest()
+        let expected = hex!("c59f682376d137f3f255e671e207d1f2374ebe504e9314208a52d9f88d69e8c8");
+
+        let mut out = out.into_iter();
+        for b in expected.iter() {
+            for i in 0..8 {
+                let c = out.next().unwrap().get_value().unwrap();
+
+                assert_eq!(c, (b >> i) & 1u8 == 1u8);
+            }
+        }
+    }
+
+    #[test]
+    fn test_blake2s_constraints() {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+        let input_bits: Vec<_> = (0..512)
+            .map(|i| {
+                AllocatedBit::alloc(cs.namespace(|| format!("input bit {}", i)), Some(true))
+                    .unwrap()
+                    .into()
+            })
+            .collect();
+        blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+        assert!(cs.is_satisfied());
+        assert_eq!(cs.num_constraints(), 21518);
+    }
+
+    #[test]
+    fn test_blake2s_precomp_constraints() {
+        // Test that 512 fixed leading bits (constants)
+        // doesn't result in more constraints.
+
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+        let input_bits: Vec<_> = (0..512)
+            .map(|_| Boolean::constant(rng.next_u32() % 2 != 0))
+            .chain((0..512).map(|i| {
+                AllocatedBit::alloc(cs.namespace(|| format!("input bit {}", i)), Some(true))
+                    .unwrap()
+                    .into()
+            }))
+            .collect();
+        blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+        assert!(cs.is_satisfied());
+        assert_eq!(cs.num_constraints(), 21518);
+    }
+
+    #[test]
+    fn test_blake2s_constant_constraints() {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+        let input_bits: Vec<_> = (0..512)
+            .map(|_| Boolean::constant(rng.next_u32() % 2 != 0))
+            .collect();
+        blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+        assert_eq!(cs.num_constraints(), 0);
+    }
+
+    #[test]
+    fn test_blake2s() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for input_len in (0..32).chain((32..256).filter(|a| a % 8 == 0)) {
+            let mut h = Blake2sParams::new()
+                .hash_length(32)
+                .personal(b"12345678")
+                .to_state();
+
+            let data: Vec<u8> = (0..input_len).map(|_| rng.next_u32() as u8).collect();
+
+            h.update(&data);
+
+            let hash_result = h.finalize();
+
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let mut input_bits = vec![];
+
+            for (byte_i, input_byte) in data.into_iter().enumerate() {
+                for bit_i in 0..8 {
+                    let cs = cs.namespace(|| format!("input bit {} {}", byte_i, bit_i));
+
+                    input_bits.push(
+                        AllocatedBit::alloc(cs, Some((input_byte >> bit_i) & 1u8 == 1u8))
+                            .unwrap()
+                            .into(),
+                    );
+                }
+            }
+
+            let r = blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut s = hash_result
+                .as_ref()
+                .iter()
+                .flat_map(|&byte| (0..8).map(move |i| (byte >> i) & 1u8 == 1u8));
+
+            for b in r {
+                match b {
+                    Boolean::Is(b) => {
+                        assert!(s.next().unwrap() == b.get_value().unwrap());
+                    }
+                    Boolean::Not(b) => {
+                        assert!(s.next().unwrap() != b.get_value().unwrap());
+                    }
+                    Boolean::Constant(b) => {
+                        assert!(input_len == 0);
+                        assert!(s.next().unwrap() == b);
+                    }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_blake2s_256_vars() {
+        let data: Vec<u8> = hex!("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").to_vec();
+        assert_eq!(data.len(), 256);
+
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        let mut input_bits = vec![];
+
+        for (byte_i, input_byte) in data.into_iter().enumerate() {
+            for bit_i in 0..8 {
+                let cs = cs.namespace(|| format!("input bit {} {}", byte_i, bit_i));
+
+                input_bits.push(
+                    AllocatedBit::alloc(cs, Some((input_byte >> bit_i) & 1u8 == 1u8))
+                        .unwrap()
+                        .into(),
+                );
+            }
+        }
+
+        let r = blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+
+        assert!(cs.is_satisfied());
+
+        let expected = hex!("0af5695115ced92c8a0341e43869209636e9aa6472e4576f0f2b996cf812b30e");
+
+        let mut out = r.into_iter();
+        for b in expected.iter() {
+            for i in 0..8 {
+                let c = out.next().unwrap().get_value().unwrap();
+
+                assert_eq!(c, (b >> i) & 1u8 == 1u8);
+            }
+        }
+    }
+
+    #[test]
+    fn test_blake2s_700_vars() {
+        let data: Vec<u8> = hex!("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").to_vec();
+        assert_eq!(data.len(), 700);
+
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        let mut input_bits = vec![];
+
+        for (byte_i, input_byte) in data.into_iter().enumerate() {
+            for bit_i in 0..8 {
+                let cs = cs.namespace(|| format!("input bit {} {}", byte_i, bit_i));
+
+                input_bits.push(
+                    AllocatedBit::alloc(cs, Some((input_byte >> bit_i) & 1u8 == 1u8))
+                        .unwrap()
+                        .into(),
+                );
+            }
+        }
+
+        let r = blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+
+        assert!(cs.is_satisfied());
+
+        let expected = hex!("2ab8f0683167ba220eef19dccf4f9b1a8193cc09b35e0235842323950530f18a");
+
+        let mut out = r.into_iter();
+        for b in expected.iter() {
+            for i in 0..8 {
+                let c = out.next().unwrap().get_value().unwrap();
+
+                assert_eq!(c, (b >> i) & 1u8 == 1u8);
+            }
+        }
+    }
+
+    #[test]
+    fn test_blake2s_test_vectors() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let expecteds = [
+            hex!("a1309e334376c8f36a736a4ab0e691ef931ee3ebdb9ea96187127136fea622a1"),
+            hex!("82fefff60f265cea255252f7c194a7f93965dffee0609ef74eb67f0d76cd41c6"),
+        ];
+        for i in 0..2 {
+            let mut h = Blake2sParams::new()
+                .hash_length(32)
+                .personal(b"12345678")
+                .to_state();
+            let input_len = 1024;
+            let data: Vec<u8> = (0..input_len).map(|_| rng.next_u32() as u8).collect();
+
+            h.update(&data);
+
+            let hash_result = h.finalize();
+
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let mut input_bits = vec![];
+
+            for (byte_i, input_byte) in data.into_iter().enumerate() {
+                for bit_i in 0..8 {
+                    let cs = cs.namespace(|| format!("input bit {} {}", byte_i, bit_i));
+
+                    input_bits.push(
+                        AllocatedBit::alloc(cs, Some((input_byte >> bit_i) & 1u8 == 1u8))
+                            .unwrap()
+                            .into(),
+                    );
+                }
+            }
+
+            let r = blake2s(&mut cs, &input_bits, b"12345678").unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut s = hash_result
+                .as_ref()
+                .iter()
+                .flat_map(|&byte| (0..8).map(move |i| (byte >> i) & 1u8 == 1u8));
+
+            for b in r {
+                match b {
+                    Boolean::Is(b) => {
+                        assert!(s.next().unwrap() == b.get_value().unwrap());
+                    }
+                    Boolean::Not(b) => {
+                        assert!(s.next().unwrap() != b.get_value().unwrap());
+                    }
+                    Boolean::Constant(b) => {
+                        assert!(input_len == 0);
+                        assert!(s.next().unwrap() == b);
+                    }
+                }
+            }
+
+            assert_eq!(expecteds[i], hash_result.as_bytes());
+        }
+    }
+}

bellman/src/gadgets/lookup.rs

@@ -0,0 +1,317 @@
+//! Window table lookup gadgets.
+
+use ff::{Field, ScalarEngine};
+
+use super::boolean::Boolean;
+use super::num::{AllocatedNum, Num};
+use super::*;
+use crate::ConstraintSystem;
+
+// Synthesize the constants for each base pattern.
+fn synth<'a, E: ScalarEngine, I>(window_size: usize, constants: I, assignment: &mut [E::Fr])
+where
+    I: IntoIterator<Item = &'a E::Fr>,
+{
+    assert_eq!(assignment.len(), 1 << window_size);
+
+    for (i, constant) in constants.into_iter().enumerate() {
+        let mut cur = assignment[i];
+        cur.negate();
+        cur.add_assign(constant);
+        assignment[i] = cur;
+        for (j, eval) in assignment.iter_mut().enumerate().skip(i + 1) {
+            if j & i == i {
+                eval.add_assign(&cur);
+            }
+        }
+    }
+}
+
+/// Performs a 3-bit window table lookup. `bits` is in
+/// little-endian order.
+pub fn lookup3_xy<E: ScalarEngine, CS>(
+    mut cs: CS,
+    bits: &[Boolean],
+    coords: &[(E::Fr, E::Fr)],
+) -> Result<(AllocatedNum<E>, AllocatedNum<E>), SynthesisError>
+where
+    CS: ConstraintSystem<E>,
+{
+    assert_eq!(bits.len(), 3);
+    assert_eq!(coords.len(), 8);
+
+    // Calculate the index into `coords`
+    let i = match (
+        bits[0].get_value(),
+        bits[1].get_value(),
+        bits[2].get_value(),
+    ) {
+        (Some(a_value), Some(b_value), Some(c_value)) => {
+            let mut tmp = 0;
+            if a_value {
+                tmp += 1;
+            }
+            if b_value {
+                tmp += 2;
+            }
+            if c_value {
+                tmp += 4;
+            }
+            Some(tmp)
+        }
+        _ => None,
+    };
+
+    // Allocate the x-coordinate resulting from the lookup
+    let res_x = AllocatedNum::alloc(cs.namespace(|| "x"), || Ok(coords[*i.get()?].0))?;
+
+    // Allocate the y-coordinate resulting from the lookup
+    let res_y = AllocatedNum::alloc(cs.namespace(|| "y"), || Ok(coords[*i.get()?].1))?;
+
+    // Compute the coefficients for the lookup constraints
+    let mut x_coeffs = [E::Fr::zero(); 8];
+    let mut y_coeffs = [E::Fr::zero(); 8];
+    synth::<E, _>(3, coords.iter().map(|c| &c.0), &mut x_coeffs);
+    synth::<E, _>(3, coords.iter().map(|c| &c.1), &mut y_coeffs);
+
+    let precomp = Boolean::and(cs.namespace(|| "precomp"), &bits[1], &bits[2])?;
+
+    let one = CS::one();
+
+    cs.enforce(
+        || "x-coordinate lookup",
+        |lc| {
+            lc + (x_coeffs[0b001], one)
+                + &bits[1].lc::<E>(one, x_coeffs[0b011])
+                + &bits[2].lc::<E>(one, x_coeffs[0b101])
+                + &precomp.lc::<E>(one, x_coeffs[0b111])
+        },
+        |lc| lc + &bits[0].lc::<E>(one, E::Fr::one()),
+        |lc| {
+            lc + res_x.get_variable()
+                - (x_coeffs[0b000], one)
+                - &bits[1].lc::<E>(one, x_coeffs[0b010])
+                - &bits[2].lc::<E>(one, x_coeffs[0b100])
+                - &precomp.lc::<E>(one, x_coeffs[0b110])
+        },
+    );
+
+    cs.enforce(
+        || "y-coordinate lookup",
+        |lc| {
+            lc + (y_coeffs[0b001], one)
+                + &bits[1].lc::<E>(one, y_coeffs[0b011])
+                + &bits[2].lc::<E>(one, y_coeffs[0b101])
+                + &precomp.lc::<E>(one, y_coeffs[0b111])
+        },
+        |lc| lc + &bits[0].lc::<E>(one, E::Fr::one()),
+        |lc| {
+            lc + res_y.get_variable()
+                - (y_coeffs[0b000], one)
+                - &bits[1].lc::<E>(one, y_coeffs[0b010])
+                - &bits[2].lc::<E>(one, y_coeffs[0b100])
+                - &precomp.lc::<E>(one, y_coeffs[0b110])
+        },
+    );
+
+    Ok((res_x, res_y))
+}
+
+/// Performs a 3-bit window table lookup, where
+/// one of the bits is a sign bit.
+pub fn lookup3_xy_with_conditional_negation<E: ScalarEngine, CS>(
+    mut cs: CS,
+    bits: &[Boolean],
+    coords: &[(E::Fr, E::Fr)],
+) -> Result<(Num<E>, Num<E>), SynthesisError>
+where
+    CS: ConstraintSystem<E>,
+{
+    assert_eq!(bits.len(), 3);
+    assert_eq!(coords.len(), 4);
+
+    // Calculate the index into `coords`
+    let i = match (bits[0].get_value(), bits[1].get_value()) {
+        (Some(a_value), Some(b_value)) => {
+            let mut tmp = 0;
+            if a_value {
+                tmp += 1;
+            }
+            if b_value {
+                tmp += 2;
+            }
+            Some(tmp)
+        }
+        _ => None,
+    };
+
+    // Allocate the y-coordinate resulting from the lookup
+    // and conditional negation
+    let y = AllocatedNum::alloc(cs.namespace(|| "y"), || {
+        let mut tmp = coords[*i.get()?].1;
+        if *bits[2].get_value().get()? {
+            tmp.negate();
+        }
+        Ok(tmp)
+    })?;
+
+    let one = CS::one();
+
+    // Compute the coefficients for the lookup constraints
+    let mut x_coeffs = [E::Fr::zero(); 4];
+    let mut y_coeffs = [E::Fr::zero(); 4];
+    synth::<E, _>(2, coords.iter().map(|c| &c.0), &mut x_coeffs);
+    synth::<E, _>(2, coords.iter().map(|c| &c.1), &mut y_coeffs);
+
+    let precomp = Boolean::and(cs.namespace(|| "precomp"), &bits[0], &bits[1])?;
+
+    let x = Num::zero()
+        .add_bool_with_coeff(one, &Boolean::constant(true), x_coeffs[0b00])
+        .add_bool_with_coeff(one, &bits[0], x_coeffs[0b01])
+        .add_bool_with_coeff(one, &bits[1], x_coeffs[0b10])
+        .add_bool_with_coeff(one, &precomp, x_coeffs[0b11]);
+
+    let y_lc = precomp.lc::<E>(one, y_coeffs[0b11])
+        + &bits[1].lc::<E>(one, y_coeffs[0b10])
+        + &bits[0].lc::<E>(one, y_coeffs[0b01])
+        + (y_coeffs[0b00], one);
+
+    cs.enforce(
+        || "y-coordinate lookup",
+        |lc| lc + &y_lc + &y_lc,
+        |lc| lc + &bits[2].lc::<E>(one, E::Fr::one()),
+        |lc| lc + &y_lc - y.get_variable(),
+    );
+
+    Ok((x, y.into()))
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::gadgets::boolean::{AllocatedBit, Boolean};
+    use crate::gadgets::test::*;
+    use pairing::bls12_381::{Bls12, Fr};
+    use rand_core::{RngCore, SeedableRng};
+    use rand_xorshift::XorShiftRng;
+
+    #[test]
+    fn test_lookup3_xy() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..100 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a_val = rng.next_u32() % 2 != 0;
+            let a = Boolean::from(AllocatedBit::alloc(cs.namespace(|| "a"), Some(a_val)).unwrap());
+
+            let b_val = rng.next_u32() % 2 != 0;
+            let b = Boolean::from(AllocatedBit::alloc(cs.namespace(|| "b"), Some(b_val)).unwrap());
+
+            let c_val = rng.next_u32() % 2 != 0;
+            let c = Boolean::from(AllocatedBit::alloc(cs.namespace(|| "c"), Some(c_val)).unwrap());
+
+            let bits = vec![a, b, c];
+
+            let points: Vec<(Fr, Fr)> = (0..8)
+                .map(|_| (Fr::random(&mut rng), Fr::random(&mut rng)))
+                .collect();
+
+            let res = lookup3_xy(&mut cs, &bits, &points).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut index = 0;
+            if a_val {
+                index += 1
+            }
+            if b_val {
+                index += 2
+            }
+            if c_val {
+                index += 4
+            }
+
+            assert_eq!(res.0.get_value().unwrap(), points[index].0);
+            assert_eq!(res.1.get_value().unwrap(), points[index].1);
+        }
+    }
+
+    #[test]
+    fn test_lookup3_xy_with_conditional_negation() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..100 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a_val = rng.next_u32() % 2 != 0;
+            let a = Boolean::from(AllocatedBit::alloc(cs.namespace(|| "a"), Some(a_val)).unwrap());
+
+            let b_val = rng.next_u32() % 2 != 0;
+            let b = Boolean::from(AllocatedBit::alloc(cs.namespace(|| "b"), Some(b_val)).unwrap());
+
+            let c_val = rng.next_u32() % 2 != 0;
+            let c = Boolean::from(AllocatedBit::alloc(cs.namespace(|| "c"), Some(c_val)).unwrap());
+
+            let bits = vec![a, b, c];
+
+            let points: Vec<(Fr, Fr)> = (0..4)
+                .map(|_| (Fr::random(&mut rng), Fr::random(&mut rng)))
+                .collect();
+
+            let res = lookup3_xy_with_conditional_negation(&mut cs, &bits, &points).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut index = 0;
+            if a_val {
+                index += 1
+            }
+            if b_val {
+                index += 2
+            }
+
+            assert_eq!(res.0.get_value().unwrap(), points[index].0);
+            let mut tmp = points[index].1;
+            if c_val {
+                tmp.negate()
+            }
+            assert_eq!(res.1.get_value().unwrap(), tmp);
+        }
+    }
+
+    #[test]
+    fn test_synth() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let window_size = 4;
+
+        let mut assignment = vec![Fr::zero(); 1 << window_size];
+        let constants: Vec<_> = (0..(1 << window_size))
+            .map(|_| Fr::random(&mut rng))
+            .collect();
+
+        synth::<Bls12, _>(window_size, &constants, &mut assignment);
+
+        for b in 0..(1 << window_size) {
+            let mut acc = Fr::zero();
+
+            for j in 0..(1 << window_size) {
+                if j & b == j {
+                    acc.add_assign(&assignment[j]);
+                }
+            }
+
+            assert_eq!(acc, constants[b]);
+        }
+    }
+}

bellman/src/gadgets/multieq.rs

@@ -0,0 +1,119 @@
+use ff::{Field, PrimeField, ScalarEngine};
+
+use crate::{ConstraintSystem, LinearCombination, SynthesisError, Variable};
+
+pub struct MultiEq<E: ScalarEngine, CS: ConstraintSystem<E>> {
+    cs: CS,
+    ops: usize,
+    bits_used: usize,
+    lhs: LinearCombination<E>,
+    rhs: LinearCombination<E>,
+}
+
+impl<E: ScalarEngine, CS: ConstraintSystem<E>> MultiEq<E, CS> {
+    pub fn new(cs: CS) -> Self {
+        MultiEq {
+            cs,
+            ops: 0,
+            bits_used: 0,
+            lhs: LinearCombination::zero(),
+            rhs: LinearCombination::zero(),
+        }
+    }
+
+    fn accumulate(&mut self) {
+        let ops = self.ops;
+        let lhs = self.lhs.clone();
+        let rhs = self.rhs.clone();
+        self.cs.enforce(
+            || format!("multieq {}", ops),
+            |_| lhs,
+            |lc| lc + CS::one(),
+            |_| rhs,
+        );
+        self.lhs = LinearCombination::zero();
+        self.rhs = LinearCombination::zero();
+        self.bits_used = 0;
+        self.ops += 1;
+    }
+
+    pub fn enforce_equal(
+        &mut self,
+        num_bits: usize,
+        lhs: &LinearCombination<E>,
+        rhs: &LinearCombination<E>,
+    ) {
+        // Check if we will exceed the capacity
+        if (E::Fr::CAPACITY as usize) <= (self.bits_used + num_bits) {
+            self.accumulate();
+        }
+
+        assert!((E::Fr::CAPACITY as usize) > (self.bits_used + num_bits));
+
+        let coeff = E::Fr::from_str("2").unwrap().pow(&[self.bits_used as u64]);
+        self.lhs = self.lhs.clone() + (coeff, lhs);
+        self.rhs = self.rhs.clone() + (coeff, rhs);
+        self.bits_used += num_bits;
+    }
+}
+
+impl<E: ScalarEngine, CS: ConstraintSystem<E>> Drop for MultiEq<E, CS> {
+    fn drop(&mut self) {
+        if self.bits_used > 0 {
+            self.accumulate();
+        }
+    }
+}
+
+impl<E: ScalarEngine, CS: ConstraintSystem<E>> ConstraintSystem<E> for MultiEq<E, CS> {
+    type Root = Self;
+
+    fn one() -> Variable {
+        CS::one()
+    }
+
+    fn alloc<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        self.cs.alloc(annotation, f)
+    }
+
+    fn alloc_input<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        self.cs.alloc_input(annotation, f)
+    }
+
+    fn enforce<A, AR, LA, LB, LC>(&mut self, annotation: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+    {
+        self.cs.enforce(annotation, a, b, c)
+    }
+
+    fn push_namespace<NR, N>(&mut self, name_fn: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        self.cs.get_root().push_namespace(name_fn)
+    }
+
+    fn pop_namespace(&mut self) {
+        self.cs.get_root().pop_namespace()
+    }
+
+    fn get_root(&mut self) -> &mut Self::Root {
+        self
+    }
+}

bellman/src/gadgets/multipack.rs

@@ -0,0 +1,111 @@
+//! Helpers for packing vectors of bits into scalar field elements.
+
+use super::boolean::Boolean;
+use super::num::Num;
+use super::Assignment;
+use crate::{ConstraintSystem, SynthesisError};
+use ff::{Field, PrimeField, ScalarEngine};
+
+/// Takes a sequence of booleans and exposes them as compact
+/// public inputs
+pub fn pack_into_inputs<E, CS>(mut cs: CS, bits: &[Boolean]) -> Result<(), SynthesisError>
+where
+    E: ScalarEngine,
+    CS: ConstraintSystem<E>,
+{
+    for (i, bits) in bits.chunks(E::Fr::CAPACITY as usize).enumerate() {
+        let mut num = Num::<E>::zero();
+        let mut coeff = E::Fr::one();
+        for bit in bits {
+            num = num.add_bool_with_coeff(CS::one(), bit, coeff);
+
+            coeff.double();
+        }
+
+        let input = cs.alloc_input(|| format!("input {}", i), || Ok(*num.get_value().get()?))?;
+
+        // num * 1 = input
+        cs.enforce(
+            || format!("packing constraint {}", i),
+            |_| num.lc(E::Fr::one()),
+            |lc| lc + CS::one(),
+            |lc| lc + input,
+        );
+    }
+
+    Ok(())
+}
+
+pub fn bytes_to_bits(bytes: &[u8]) -> Vec<bool> {
+    bytes
+        .iter()
+        .flat_map(|&v| (0..8).rev().map(move |i| (v >> i) & 1 == 1))
+        .collect()
+}
+
+pub fn bytes_to_bits_le(bytes: &[u8]) -> Vec<bool> {
+    bytes
+        .iter()
+        .flat_map(|&v| (0..8).map(move |i| (v >> i) & 1 == 1))
+        .collect()
+}
+
+pub fn compute_multipacking<E: ScalarEngine>(bits: &[bool]) -> Vec<E::Fr> {
+    let mut result = vec![];
+
+    for bits in bits.chunks(E::Fr::CAPACITY as usize) {
+        let mut cur = E::Fr::zero();
+        let mut coeff = E::Fr::one();
+
+        for bit in bits {
+            if *bit {
+                cur.add_assign(&coeff);
+            }
+
+            coeff.double();
+        }
+
+        result.push(cur);
+    }
+
+    result
+}
+
+#[test]
+fn test_multipacking() {
+    use crate::ConstraintSystem;
+    use pairing::bls12_381::Bls12;
+    use rand_core::{RngCore, SeedableRng};
+    use rand_xorshift::XorShiftRng;
+
+    use super::boolean::{AllocatedBit, Boolean};
+    use crate::gadgets::test::*;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for num_bits in 0..1500 {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        let bits: Vec<bool> = (0..num_bits).map(|_| rng.next_u32() % 2 != 0).collect();
+
+        let circuit_bits = bits
+            .iter()
+            .enumerate()
+            .map(|(i, &b)| {
+                Boolean::from(
+                    AllocatedBit::alloc(cs.namespace(|| format!("bit {}", i)), Some(b)).unwrap(),
+                )
+            })
+            .collect::<Vec<_>>();
+
+        let expected_inputs = compute_multipacking::<Bls12>(&bits);
+
+        pack_into_inputs(cs.namespace(|| "pack"), &circuit_bits).unwrap();
+
+        assert!(cs.is_satisfied());
+        assert!(cs.verify(&expected_inputs));
+    }
+}

bellman/src/gadgets/num.rs

@@ -0,0 +1,589 @@
+//! Gadgets representing numbers in the scalar field of the underlying curve.
+
+use ff::{BitIterator, Field, PrimeField, PrimeFieldRepr, ScalarEngine};
+
+use crate::{ConstraintSystem, LinearCombination, SynthesisError, Variable};
+
+use super::Assignment;
+
+use super::boolean::{self, AllocatedBit, Boolean};
+
+pub struct AllocatedNum<E: ScalarEngine> {
+    value: Option<E::Fr>,
+    variable: Variable,
+}
+
+impl<E: ScalarEngine> Clone for AllocatedNum<E> {
+    fn clone(&self) -> Self {
+        AllocatedNum {
+            value: self.value,
+            variable: self.variable,
+        }
+    }
+}
+
+impl<E: ScalarEngine> AllocatedNum<E> {
+    pub fn alloc<CS, F>(mut cs: CS, value: F) -> Result<Self, SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+    {
+        let mut new_value = None;
+        let var = cs.alloc(
+            || "num",
+            || {
+                let tmp = value()?;
+
+                new_value = Some(tmp);
+
+                Ok(tmp)
+            },
+        )?;
+
+        Ok(AllocatedNum {
+            value: new_value,
+            variable: var,
+        })
+    }
+
+    pub fn inputize<CS>(&self, mut cs: CS) -> Result<(), SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        let input = cs.alloc_input(|| "input variable", || Ok(*self.value.get()?))?;
+
+        cs.enforce(
+            || "enforce input is correct",
+            |lc| lc + input,
+            |lc| lc + CS::one(),
+            |lc| lc + self.variable,
+        );
+
+        Ok(())
+    }
+
+    /// Deconstructs this allocated number into its
+    /// boolean representation in little-endian bit
+    /// order, requiring that the representation
+    /// strictly exists "in the field" (i.e., a
+    /// congruency is not allowed.)
+    pub fn to_bits_le_strict<CS>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        pub fn kary_and<E, CS>(
+            mut cs: CS,
+            v: &[AllocatedBit],
+        ) -> Result<AllocatedBit, SynthesisError>
+        where
+            E: ScalarEngine,
+            CS: ConstraintSystem<E>,
+        {
+            assert!(!v.is_empty());
+
+            // Let's keep this simple for now and just AND them all
+            // manually
+            let mut cur = None;
+
+            for (i, v) in v.iter().enumerate() {
+                if cur.is_none() {
+                    cur = Some(v.clone());
+                } else {
+                    cur = Some(AllocatedBit::and(
+                        cs.namespace(|| format!("and {}", i)),
+                        cur.as_ref().unwrap(),
+                        v,
+                    )?);
+                }
+            }
+
+            Ok(cur.expect("v.len() > 0"))
+        }
+
+        // We want to ensure that the bit representation of a is
+        // less than or equal to r - 1.
+        let mut a = self.value.map(|e| BitIterator::new(e.into_repr()));
+        let mut b = E::Fr::char();
+        b.sub_noborrow(&1.into());
+
+        let mut result = vec![];
+
+        // Runs of ones in r
+        let mut last_run = None;
+        let mut current_run = vec![];
+
+        let mut found_one = false;
+        let mut i = 0;
+        for b in BitIterator::new(b) {
+            let a_bit = a.as_mut().map(|e| e.next().unwrap());
+
+            // Skip over unset bits at the beginning
+            found_one |= b;
+            if !found_one {
+                // a_bit should also be false
+                a_bit.map(|e| assert!(!e));
+                continue;
+            }
+
+            if b {
+                // This is part of a run of ones. Let's just
+                // allocate the boolean with the expected value.
+                let a_bit = AllocatedBit::alloc(cs.namespace(|| format!("bit {}", i)), a_bit)?;
+                // ... and add it to the current run of ones.
+                current_run.push(a_bit.clone());
+                result.push(a_bit);
+            } else {
+                if !current_run.is_empty() {
+                    // This is the start of a run of zeros, but we need
+                    // to k-ary AND against `last_run` first.
+
+                    if last_run.is_some() {
+                        current_run.push(last_run.clone().unwrap());
+                    }
+                    last_run = Some(kary_and(
+                        cs.namespace(|| format!("run ending at {}", i)),
+                        &current_run,
+                    )?);
+                    current_run.truncate(0);
+                }
+
+                // If `last_run` is true, `a` must be false, or it would
+                // not be in the field.
+                //
+                // If `last_run` is false, `a` can be true or false.
+
+                let a_bit = AllocatedBit::alloc_conditionally(
+                    cs.namespace(|| format!("bit {}", i)),
+                    a_bit,
+                    &last_run.as_ref().expect("char always starts with a one"),
+                )?;
+                result.push(a_bit);
+            }
+
+            i += 1;
+        }
+
+        // char is prime, so we'll always end on
+        // a run of zeros.
+        assert_eq!(current_run.len(), 0);
+
+        // Now, we have `result` in big-endian order.
+        // However, now we have to unpack self!
+
+        let mut lc = LinearCombination::zero();
+        let mut coeff = E::Fr::one();
+
+        for bit in result.iter().rev() {
+            lc = lc + (coeff, bit.get_variable());
+
+            coeff.double();
+        }
+
+        lc = lc - self.variable;
+
+        cs.enforce(|| "unpacking constraint", |lc| lc, |lc| lc, |_| lc);
+
+        // Convert into booleans, and reverse for little-endian bit order
+        Ok(result.into_iter().map(Boolean::from).rev().collect())
+    }
+
+    /// Convert the allocated number into its little-endian representation.
+    /// Note that this does not strongly enforce that the commitment is
+    /// "in the field."
+    pub fn to_bits_le<CS>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        let bits = boolean::field_into_allocated_bits_le(&mut cs, self.value)?;
+
+        let mut lc = LinearCombination::zero();
+        let mut coeff = E::Fr::one();
+
+        for bit in bits.iter() {
+            lc = lc + (coeff, bit.get_variable());
+
+            coeff.double();
+        }
+
+        lc = lc - self.variable;
+
+        cs.enforce(|| "unpacking constraint", |lc| lc, |lc| lc, |_| lc);
+
+        Ok(bits.into_iter().map(Boolean::from).collect())
+    }
+
+    pub fn mul<CS>(&self, mut cs: CS, other: &Self) -> Result<Self, SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        let mut value = None;
+
+        let var = cs.alloc(
+            || "product num",
+            || {
+                let mut tmp = *self.value.get()?;
+                tmp.mul_assign(other.value.get()?);
+
+                value = Some(tmp);
+
+                Ok(tmp)
+            },
+        )?;
+
+        // Constrain: a * b = ab
+        cs.enforce(
+            || "multiplication constraint",
+            |lc| lc + self.variable,
+            |lc| lc + other.variable,
+            |lc| lc + var,
+        );
+
+        Ok(AllocatedNum {
+            value,
+            variable: var,
+        })
+    }
+
+    pub fn square<CS>(&self, mut cs: CS) -> Result<Self, SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        let mut value = None;
+
+        let var = cs.alloc(
+            || "squared num",
+            || {
+                let mut tmp = *self.value.get()?;
+                tmp.square();
+
+                value = Some(tmp);
+
+                Ok(tmp)
+            },
+        )?;
+
+        // Constrain: a * a = aa
+        cs.enforce(
+            || "squaring constraint",
+            |lc| lc + self.variable,
+            |lc| lc + self.variable,
+            |lc| lc + var,
+        );
+
+        Ok(AllocatedNum {
+            value,
+            variable: var,
+        })
+    }
+
+    pub fn assert_nonzero<CS>(&self, mut cs: CS) -> Result<(), SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        let inv = cs.alloc(
+            || "ephemeral inverse",
+            || {
+                let tmp = *self.value.get()?;
+
+                if tmp.is_zero() {
+                    Err(SynthesisError::DivisionByZero)
+                } else {
+                    Ok(tmp.inverse().unwrap())
+                }
+            },
+        )?;
+
+        // Constrain a * inv = 1, which is only valid
+        // iff a has a multiplicative inverse, untrue
+        // for zero.
+        cs.enforce(
+            || "nonzero assertion constraint",
+            |lc| lc + self.variable,
+            |lc| lc + inv,
+            |lc| lc + CS::one(),
+        );
+
+        Ok(())
+    }
+
+    /// Takes two allocated numbers (a, b) and returns
+    /// (b, a) if the condition is true, and (a, b)
+    /// otherwise.
+    pub fn conditionally_reverse<CS>(
+        mut cs: CS,
+        a: &Self,
+        b: &Self,
+        condition: &Boolean,
+    ) -> Result<(Self, Self), SynthesisError>
+    where
+        CS: ConstraintSystem<E>,
+    {
+        let c = Self::alloc(cs.namespace(|| "conditional reversal result 1"), || {
+            if *condition.get_value().get()? {
+                Ok(*b.value.get()?)
+            } else {
+                Ok(*a.value.get()?)
+            }
+        })?;
+
+        cs.enforce(
+            || "first conditional reversal",
+            |lc| lc + a.variable - b.variable,
+            |_| condition.lc(CS::one(), E::Fr::one()),
+            |lc| lc + a.variable - c.variable,
+        );
+
+        let d = Self::alloc(cs.namespace(|| "conditional reversal result 2"), || {
+            if *condition.get_value().get()? {
+                Ok(*a.value.get()?)
+            } else {
+                Ok(*b.value.get()?)
+            }
+        })?;
+
+        cs.enforce(
+            || "second conditional reversal",
+            |lc| lc + b.variable - a.variable,
+            |_| condition.lc(CS::one(), E::Fr::one()),
+            |lc| lc + b.variable - d.variable,
+        );
+
+        Ok((c, d))
+    }
+
+    pub fn get_value(&self) -> Option<E::Fr> {
+        self.value
+    }
+
+    pub fn get_variable(&self) -> Variable {
+        self.variable
+    }
+}
+
+pub struct Num<E: ScalarEngine> {
+    value: Option<E::Fr>,
+    lc: LinearCombination<E>,
+}
+
+impl<E: ScalarEngine> From<AllocatedNum<E>> for Num<E> {
+    fn from(num: AllocatedNum<E>) -> Num<E> {
+        Num {
+            value: num.value,
+            lc: LinearCombination::<E>::zero() + num.variable,
+        }
+    }
+}
+
+impl<E: ScalarEngine> Num<E> {
+    pub fn zero() -> Self {
+        Num {
+            value: Some(E::Fr::zero()),
+            lc: LinearCombination::zero(),
+        }
+    }
+
+    pub fn get_value(&self) -> Option<E::Fr> {
+        self.value
+    }
+
+    pub fn lc(&self, coeff: E::Fr) -> LinearCombination<E> {
+        LinearCombination::zero() + (coeff, &self.lc)
+    }
+
+    pub fn add_bool_with_coeff(self, one: Variable, bit: &Boolean, coeff: E::Fr) -> Self {
+        let newval = match (self.value, bit.get_value()) {
+            (Some(mut curval), Some(bval)) => {
+                if bval {
+                    curval.add_assign(&coeff);
+                }
+
+                Some(curval)
+            }
+            _ => None,
+        };
+
+        Num {
+            value: newval,
+            lc: self.lc + &bit.lc(one, coeff),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::ConstraintSystem;
+    use ff::{BitIterator, Field, PrimeField};
+    use pairing::bls12_381::{Bls12, Fr};
+    use rand_core::SeedableRng;
+    use rand_xorshift::XorShiftRng;
+
+    use super::{AllocatedNum, Boolean};
+    use crate::gadgets::test::*;
+
+    #[test]
+    fn test_allocated_num() {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        AllocatedNum::alloc(&mut cs, || Ok(Fr::one())).unwrap();
+
+        assert!(cs.get("num") == Fr::one());
+    }
+
+    #[test]
+    fn test_num_squaring() {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        let n = AllocatedNum::alloc(&mut cs, || Ok(Fr::from_str("3").unwrap())).unwrap();
+        let n2 = n.square(&mut cs).unwrap();
+
+        assert!(cs.is_satisfied());
+        assert!(cs.get("squared num") == Fr::from_str("9").unwrap());
+        assert!(n2.value.unwrap() == Fr::from_str("9").unwrap());
+        cs.set("squared num", Fr::from_str("10").unwrap());
+        assert!(!cs.is_satisfied());
+    }
+
+    #[test]
+    fn test_num_multiplication() {
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        let n =
+            AllocatedNum::alloc(cs.namespace(|| "a"), || Ok(Fr::from_str("12").unwrap())).unwrap();
+        let n2 =
+            AllocatedNum::alloc(cs.namespace(|| "b"), || Ok(Fr::from_str("10").unwrap())).unwrap();
+        let n3 = n.mul(&mut cs, &n2).unwrap();
+
+        assert!(cs.is_satisfied());
+        assert!(cs.get("product num") == Fr::from_str("120").unwrap());
+        assert!(n3.value.unwrap() == Fr::from_str("120").unwrap());
+        cs.set("product num", Fr::from_str("121").unwrap());
+        assert!(!cs.is_satisfied());
+    }
+
+    #[test]
+    fn test_num_conditional_reversal() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+        {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = AllocatedNum::alloc(cs.namespace(|| "a"), || Ok(Fr::random(&mut rng))).unwrap();
+            let b = AllocatedNum::alloc(cs.namespace(|| "b"), || Ok(Fr::random(&mut rng))).unwrap();
+            let condition = Boolean::constant(false);
+            let (c, d) = AllocatedNum::conditionally_reverse(&mut cs, &a, &b, &condition).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            assert_eq!(a.value.unwrap(), c.value.unwrap());
+            assert_eq!(b.value.unwrap(), d.value.unwrap());
+        }
+
+        {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = AllocatedNum::alloc(cs.namespace(|| "a"), || Ok(Fr::random(&mut rng))).unwrap();
+            let b = AllocatedNum::alloc(cs.namespace(|| "b"), || Ok(Fr::random(&mut rng))).unwrap();
+            let condition = Boolean::constant(true);
+            let (c, d) = AllocatedNum::conditionally_reverse(&mut cs, &a, &b, &condition).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            assert_eq!(a.value.unwrap(), d.value.unwrap());
+            assert_eq!(b.value.unwrap(), c.value.unwrap());
+        }
+    }
+
+    #[test]
+    fn test_num_nonzero() {
+        {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let n = AllocatedNum::alloc(&mut cs, || Ok(Fr::from_str("3").unwrap())).unwrap();
+            n.assert_nonzero(&mut cs).unwrap();
+
+            assert!(cs.is_satisfied());
+            cs.set("ephemeral inverse", Fr::from_str("3").unwrap());
+            assert!(cs.which_is_unsatisfied() == Some("nonzero assertion constraint"));
+        }
+        {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let n = AllocatedNum::alloc(&mut cs, || Ok(Fr::zero())).unwrap();
+            assert!(n.assert_nonzero(&mut cs).is_err());
+        }
+    }
+
+    #[test]
+    fn test_into_bits_strict() {
+        let mut negone = Fr::one();
+        negone.negate();
+
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+
+        let n = AllocatedNum::alloc(&mut cs, || Ok(negone)).unwrap();
+        n.to_bits_le_strict(&mut cs).unwrap();
+
+        assert!(cs.is_satisfied());
+
+        // make the bit representation the characteristic
+        cs.set("bit 254/boolean", Fr::one());
+
+        // this makes the conditional boolean constraint fail
+        assert_eq!(
+            cs.which_is_unsatisfied().unwrap(),
+            "bit 254/boolean constraint"
+        );
+    }
+
+    #[test]
+    fn test_into_bits() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for i in 0..200 {
+            let r = Fr::random(&mut rng);
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let n = AllocatedNum::alloc(&mut cs, || Ok(r)).unwrap();
+
+            let bits = if i % 2 == 0 {
+                n.to_bits_le(&mut cs).unwrap()
+            } else {
+                n.to_bits_le_strict(&mut cs).unwrap()
+            };
+
+            assert!(cs.is_satisfied());
+
+            for (b, a) in BitIterator::new(r.into_repr())
+                .skip(1)
+                .zip(bits.iter().rev())
+            {
+                if let &Boolean::Is(ref a) = a {
+                    assert_eq!(b, a.get_value().unwrap());
+                } else {
+                    unreachable!()
+                }
+            }
+
+            cs.set("num", Fr::random(&mut rng));
+            assert!(!cs.is_satisfied());
+            cs.set("num", r);
+            assert!(cs.is_satisfied());
+
+            for i in 0..Fr::NUM_BITS {
+                let name = format!("bit {}/boolean", i);
+                let cur = cs.get(&name);
+                let mut tmp = Fr::one();
+                tmp.sub_assign(&cur);
+                cs.set(&name, tmp);
+                assert!(!cs.is_satisfied());
+                cs.set(&name, cur);
+                assert!(cs.is_satisfied());
+            }
+        }
+    }
+}

bellman/src/gadgets/sha256.rs

@@ -0,0 +1,389 @@
+//! Circuits for the [SHA-256] hash function and its internal compression
+//! function.
+//!
+//! [SHA-256]: https://tools.ietf.org/html/rfc6234
+
+use super::boolean::Boolean;
+use super::multieq::MultiEq;
+use super::uint32::UInt32;
+use crate::{ConstraintSystem, SynthesisError};
+use ff::ScalarEngine;
+
+#[allow(clippy::unreadable_literal)]
+const ROUND_CONSTANTS: [u32; 64] = [
+    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+];
+
+#[allow(clippy::unreadable_literal)]
+const IV: [u32; 8] = [
+    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19,
+];
+
+pub fn sha256_block_no_padding<E, CS>(
+    mut cs: CS,
+    input: &[Boolean],
+) -> Result<Vec<Boolean>, SynthesisError>
+where
+    E: ScalarEngine,
+    CS: ConstraintSystem<E>,
+{
+    assert_eq!(input.len(), 512);
+
+    Ok(
+        sha256_compression_function(&mut cs, &input, &get_sha256_iv())?
+            .into_iter()
+            .flat_map(|e| e.into_bits_be())
+            .collect(),
+    )
+}
+
+pub fn sha256<E, CS>(mut cs: CS, input: &[Boolean]) -> Result<Vec<Boolean>, SynthesisError>
+where
+    E: ScalarEngine,
+    CS: ConstraintSystem<E>,
+{
+    assert!(input.len() % 8 == 0);
+
+    let mut padded = input.to_vec();
+    let plen = padded.len() as u64;
+    // append a single '1' bit
+    padded.push(Boolean::constant(true));
+    // append K '0' bits, where K is the minimum number >= 0 such that L + 1 + K + 64 is a multiple of 512
+    while (padded.len() + 64) % 512 != 0 {
+        padded.push(Boolean::constant(false));
+    }
+    // append L as a 64-bit big-endian integer, making the total post-processed length a multiple of 512 bits
+    for b in (0..64).rev().map(|i| (plen >> i) & 1 == 1) {
+        padded.push(Boolean::constant(b));
+    }
+    assert!(padded.len() % 512 == 0);
+
+    let mut cur = get_sha256_iv();
+    for (i, block) in padded.chunks(512).enumerate() {
+        cur = sha256_compression_function(cs.namespace(|| format!("block {}", i)), block, &cur)?;
+    }
+
+    Ok(cur.into_iter().flat_map(|e| e.into_bits_be()).collect())
+}
+
+fn get_sha256_iv() -> Vec<UInt32> {
+    IV.iter().map(|&v| UInt32::constant(v)).collect()
+}
+
+fn sha256_compression_function<E, CS>(
+    cs: CS,
+    input: &[Boolean],
+    current_hash_value: &[UInt32],
+) -> Result<Vec<UInt32>, SynthesisError>
+where
+    E: ScalarEngine,
+    CS: ConstraintSystem<E>,
+{
+    assert_eq!(input.len(), 512);
+    assert_eq!(current_hash_value.len(), 8);
+
+    let mut w = input
+        .chunks(32)
+        .map(|e| UInt32::from_bits_be(e))
+        .collect::<Vec<_>>();
+
+    // We can save some constraints by combining some of
+    // the constraints in different u32 additions
+    let mut cs = MultiEq::new(cs);
+
+    for i in 16..64 {
+        let cs = &mut cs.namespace(|| format!("w extension {}", i));
+
+        // s0 := (w[i-15] rightrotate 7) xor (w[i-15] rightrotate 18) xor (w[i-15] rightshift 3)
+        let mut s0 = w[i - 15].rotr(7);
+        s0 = s0.xor(cs.namespace(|| "first xor for s0"), &w[i - 15].rotr(18))?;
+        s0 = s0.xor(cs.namespace(|| "second xor for s0"), &w[i - 15].shr(3))?;
+
+        // s1 := (w[i-2] rightrotate 17) xor (w[i-2] rightrotate 19) xor (w[i-2] rightshift 10)
+        let mut s1 = w[i - 2].rotr(17);
+        s1 = s1.xor(cs.namespace(|| "first xor for s1"), &w[i - 2].rotr(19))?;
+        s1 = s1.xor(cs.namespace(|| "second xor for s1"), &w[i - 2].shr(10))?;
+
+        let tmp = UInt32::addmany(
+            cs.namespace(|| "computation of w[i]"),
+            &[w[i - 16].clone(), s0, w[i - 7].clone(), s1],
+        )?;
+
+        // w[i] := w[i-16] + s0 + w[i-7] + s1
+        w.push(tmp);
+    }
+
+    assert_eq!(w.len(), 64);
+
+    enum Maybe {
+        Deferred(Vec<UInt32>),
+        Concrete(UInt32),
+    }
+
+    impl Maybe {
+        fn compute<E, CS, M>(self, cs: M, others: &[UInt32]) -> Result<UInt32, SynthesisError>
+        where
+            E: ScalarEngine,
+            CS: ConstraintSystem<E>,
+            M: ConstraintSystem<E, Root = MultiEq<E, CS>>,
+        {
+            Ok(match self {
+                Maybe::Concrete(ref v) => return Ok(v.clone()),
+                Maybe::Deferred(mut v) => {
+                    v.extend(others.iter().cloned());
+                    UInt32::addmany(cs, &v)?
+                }
+            })
+        }
+    }
+
+    let mut a = Maybe::Concrete(current_hash_value[0].clone());
+    let mut b = current_hash_value[1].clone();
+    let mut c = current_hash_value[2].clone();
+    let mut d = current_hash_value[3].clone();
+    let mut e = Maybe::Concrete(current_hash_value[4].clone());
+    let mut f = current_hash_value[5].clone();
+    let mut g = current_hash_value[6].clone();
+    let mut h = current_hash_value[7].clone();
+
+    for i in 0..64 {
+        let cs = &mut cs.namespace(|| format!("compression round {}", i));
+
+        // S1 := (e rightrotate 6) xor (e rightrotate 11) xor (e rightrotate 25)
+        let new_e = e.compute(cs.namespace(|| "deferred e computation"), &[])?;
+        let mut s1 = new_e.rotr(6);
+        s1 = s1.xor(cs.namespace(|| "first xor for s1"), &new_e.rotr(11))?;
+        s1 = s1.xor(cs.namespace(|| "second xor for s1"), &new_e.rotr(25))?;
+
+        // ch := (e and f) xor ((not e) and g)
+        let ch = UInt32::sha256_ch(cs.namespace(|| "ch"), &new_e, &f, &g)?;
+
+        // temp1 := h + S1 + ch + k[i] + w[i]
+        let temp1 = vec![
+            h.clone(),
+            s1,
+            ch,
+            UInt32::constant(ROUND_CONSTANTS[i]),
+            w[i].clone(),
+        ];
+
+        // S0 := (a rightrotate 2) xor (a rightrotate 13) xor (a rightrotate 22)
+        let new_a = a.compute(cs.namespace(|| "deferred a computation"), &[])?;
+        let mut s0 = new_a.rotr(2);
+        s0 = s0.xor(cs.namespace(|| "first xor for s0"), &new_a.rotr(13))?;
+        s0 = s0.xor(cs.namespace(|| "second xor for s0"), &new_a.rotr(22))?;
+
+        // maj := (a and b) xor (a and c) xor (b and c)
+        let maj = UInt32::sha256_maj(cs.namespace(|| "maj"), &new_a, &b, &c)?;
+
+        // temp2 := S0 + maj
+        let temp2 = vec![s0, maj];
+
+        /*
+        h := g
+        g := f
+        f := e
+        e := d + temp1
+        d := c
+        c := b
+        b := a
+        a := temp1 + temp2
+        */
+
+        h = g;
+        g = f;
+        f = new_e;
+        e = Maybe::Deferred(temp1.iter().cloned().chain(Some(d)).collect::<Vec<_>>());
+        d = c;
+        c = b;
+        b = new_a;
+        a = Maybe::Deferred(
+            temp1
+                .iter()
+                .cloned()
+                .chain(temp2.iter().cloned())
+                .collect::<Vec<_>>(),
+        );
+    }
+
+    /*
+        Add the compressed chunk to the current hash value:
+        h0 := h0 + a
+        h1 := h1 + b
+        h2 := h2 + c
+        h3 := h3 + d
+        h4 := h4 + e
+        h5 := h5 + f
+        h6 := h6 + g
+        h7 := h7 + h
+    */
+
+    let h0 = a.compute(
+        cs.namespace(|| "deferred h0 computation"),
+        &[current_hash_value[0].clone()],
+    )?;
+
+    let h1 = UInt32::addmany(
+        cs.namespace(|| "new h1"),
+        &[current_hash_value[1].clone(), b],
+    )?;
+
+    let h2 = UInt32::addmany(
+        cs.namespace(|| "new h2"),
+        &[current_hash_value[2].clone(), c],
+    )?;
+
+    let h3 = UInt32::addmany(
+        cs.namespace(|| "new h3"),
+        &[current_hash_value[3].clone(), d],
+    )?;
+
+    let h4 = e.compute(
+        cs.namespace(|| "deferred h4 computation"),
+        &[current_hash_value[4].clone()],
+    )?;
+
+    let h5 = UInt32::addmany(
+        cs.namespace(|| "new h5"),
+        &[current_hash_value[5].clone(), f],
+    )?;
+
+    let h6 = UInt32::addmany(
+        cs.namespace(|| "new h6"),
+        &[current_hash_value[6].clone(), g],
+    )?;
+
+    let h7 = UInt32::addmany(
+        cs.namespace(|| "new h7"),
+        &[current_hash_value[7].clone(), h],
+    )?;
+
+    Ok(vec![h0, h1, h2, h3, h4, h5, h6, h7])
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::gadgets::boolean::AllocatedBit;
+    use crate::gadgets::test::TestConstraintSystem;
+    use hex_literal::hex;
+    use pairing::bls12_381::Bls12;
+    use rand_core::{RngCore, SeedableRng};
+    use rand_xorshift::XorShiftRng;
+
+    #[test]
+    fn test_blank_hash() {
+        let iv = get_sha256_iv();
+
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+        let mut input_bits: Vec<_> = (0..512).map(|_| Boolean::Constant(false)).collect();
+        input_bits[0] = Boolean::Constant(true);
+        let out = sha256_compression_function(&mut cs, &input_bits, &iv).unwrap();
+        let out_bits: Vec<_> = out.into_iter().flat_map(|e| e.into_bits_be()).collect();
+
+        assert!(cs.is_satisfied());
+        assert_eq!(cs.num_constraints(), 0);
+
+        let expected = hex!("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");
+
+        let mut out = out_bits.into_iter();
+        for b in expected.iter() {
+            for i in (0..8).rev() {
+                let c = out.next().unwrap().get_value().unwrap();
+
+                assert_eq!(c, (b >> i) & 1u8 == 1u8);
+            }
+        }
+    }
+
+    #[test]
+    fn test_full_block() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let iv = get_sha256_iv();
+
+        let mut cs = TestConstraintSystem::<Bls12>::new();
+        let input_bits: Vec<_> = (0..512)
+            .map(|i| {
+                Boolean::from(
+                    AllocatedBit::alloc(
+                        cs.namespace(|| format!("input bit {}", i)),
+                        Some(rng.next_u32() % 2 != 0),
+                    )
+                    .unwrap(),
+                )
+            })
+            .collect();
+
+        sha256_compression_function(cs.namespace(|| "sha256"), &input_bits, &iv).unwrap();
+
+        assert!(cs.is_satisfied());
+        assert_eq!(cs.num_constraints() - 512, 25840);
+    }
+
+    #[test]
+    fn test_against_vectors() {
+        use sha2::{Digest, Sha256};
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x3d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for input_len in (0..32).chain((32..256).filter(|a| a % 8 == 0)) {
+            let mut h = Sha256::new();
+            let data: Vec<u8> = (0..input_len).map(|_| rng.next_u32() as u8).collect();
+            h.input(&data);
+            let hash_result = h.result();
+
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+            let mut input_bits = vec![];
+
+            for (byte_i, input_byte) in data.into_iter().enumerate() {
+                for bit_i in (0..8).rev() {
+                    let cs = cs.namespace(|| format!("input bit {} {}", byte_i, bit_i));
+
+                    input_bits.push(
+                        AllocatedBit::alloc(cs, Some((input_byte >> bit_i) & 1u8 == 1u8))
+                            .unwrap()
+                            .into(),
+                    );
+                }
+            }
+
+            let r = sha256(&mut cs, &input_bits).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut s = hash_result
+                .as_ref()
+                .iter()
+                .flat_map(|&byte| (0..8).rev().map(move |i| (byte >> i) & 1u8 == 1u8));
+
+            for b in r {
+                match b {
+                    Boolean::Is(b) => {
+                        assert!(s.next().unwrap() == b.get_value().unwrap());
+                    }
+                    Boolean::Not(b) => {
+                        assert!(s.next().unwrap() != b.get_value().unwrap());
+                    }
+                    Boolean::Constant(b) => {
+                        assert!(input_len == 0);
+                        assert!(s.next().unwrap() == b);
+                    }
+                }
+            }
+        }
+    }
+}

bellman/src/gadgets/test/mod.rs

@@ -0,0 +1,464 @@
+//! Helpers for testing circuit implementations.
+
+use ff::{Field, PrimeField, PrimeFieldRepr, ScalarEngine};
+
+use crate::{ConstraintSystem, Index, LinearCombination, SynthesisError, Variable};
+
+use std::collections::HashMap;
+use std::fmt::Write;
+
+use byteorder::{BigEndian, ByteOrder};
+use std::cmp::Ordering;
+use std::collections::BTreeMap;
+
+use blake2s_simd::{Params as Blake2sParams, State as Blake2sState};
+
+#[derive(Debug)]
+enum NamedObject {
+    Constraint(usize),
+    Var(Variable),
+    Namespace,
+}
+
+/// Constraint system for testing purposes.
+pub struct TestConstraintSystem<E: ScalarEngine> {
+    named_objects: HashMap<String, NamedObject>,
+    current_namespace: Vec<String>,
+    constraints: Vec<(
+        LinearCombination<E>,
+        LinearCombination<E>,
+        LinearCombination<E>,
+        String,
+    )>,
+    inputs: Vec<(E::Fr, String)>,
+    aux: Vec<(E::Fr, String)>,
+}
+
+#[derive(Clone, Copy)]
+struct OrderedVariable(Variable);
+
+impl Eq for OrderedVariable {}
+impl PartialEq for OrderedVariable {
+    fn eq(&self, other: &OrderedVariable) -> bool {
+        match (self.0.get_unchecked(), other.0.get_unchecked()) {
+            (Index::Input(ref a), Index::Input(ref b)) => a == b,
+            (Index::Aux(ref a), Index::Aux(ref b)) => a == b,
+            _ => false,
+        }
+    }
+}
+impl PartialOrd for OrderedVariable {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+impl Ord for OrderedVariable {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self.0.get_unchecked(), other.0.get_unchecked()) {
+            (Index::Input(ref a), Index::Input(ref b)) => a.cmp(b),
+            (Index::Aux(ref a), Index::Aux(ref b)) => a.cmp(b),
+            (Index::Input(_), Index::Aux(_)) => Ordering::Less,
+            (Index::Aux(_), Index::Input(_)) => Ordering::Greater,
+        }
+    }
+}
+
+fn proc_lc<E: ScalarEngine>(terms: &[(Variable, E::Fr)]) -> BTreeMap<OrderedVariable, E::Fr> {
+    let mut map = BTreeMap::new();
+    for &(var, coeff) in terms {
+        map.entry(OrderedVariable(var))
+            .or_insert_with(E::Fr::zero)
+            .add_assign(&coeff);
+    }
+
+    // Remove terms that have a zero coefficient to normalize
+    let mut to_remove = vec![];
+    for (var, coeff) in map.iter() {
+        if coeff.is_zero() {
+            to_remove.push(var.clone())
+        }
+    }
+
+    for var in to_remove {
+        map.remove(&var);
+    }
+
+    map
+}
+
+fn hash_lc<E: ScalarEngine>(terms: &[(Variable, E::Fr)], h: &mut Blake2sState) {
+    let map = proc_lc::<E>(terms);
+
+    let mut buf = [0u8; 9 + 32];
+    BigEndian::write_u64(&mut buf[0..8], map.len() as u64);
+    h.update(&buf[0..8]);
+
+    for (var, coeff) in map {
+        match var.0.get_unchecked() {
+            Index::Input(i) => {
+                buf[0] = b'I';
+                BigEndian::write_u64(&mut buf[1..9], i as u64);
+            }
+            Index::Aux(i) => {
+                buf[0] = b'A';
+                BigEndian::write_u64(&mut buf[1..9], i as u64);
+            }
+        }
+
+        coeff.into_repr().write_be(&mut buf[9..]).unwrap();
+
+        h.update(&buf);
+    }
+}
+
+fn eval_lc<E: ScalarEngine>(
+    terms: &[(Variable, E::Fr)],
+    inputs: &[(E::Fr, String)],
+    aux: &[(E::Fr, String)],
+) -> E::Fr {
+    let mut acc = E::Fr::zero();
+
+    for &(var, ref coeff) in terms {
+        let mut tmp = match var.get_unchecked() {
+            Index::Input(index) => inputs[index].0,
+            Index::Aux(index) => aux[index].0,
+        };
+
+        tmp.mul_assign(&coeff);
+        acc.add_assign(&tmp);
+    }
+
+    acc
+}
+
+impl<E: ScalarEngine> TestConstraintSystem<E> {
+    pub fn new() -> TestConstraintSystem<E> {
+        let mut map = HashMap::new();
+        map.insert(
+            "ONE".into(),
+            NamedObject::Var(TestConstraintSystem::<E>::one()),
+        );
+
+        TestConstraintSystem {
+            named_objects: map,
+            current_namespace: vec![],
+            constraints: vec![],
+            inputs: vec![(E::Fr::one(), "ONE".into())],
+            aux: vec![],
+        }
+    }
+
+    pub fn pretty_print(&self) -> String {
+        let mut s = String::new();
+
+        let negone = {
+            let mut tmp = E::Fr::one();
+            tmp.negate();
+            tmp
+        };
+
+        let powers_of_two = (0..E::Fr::NUM_BITS)
+            .map(|i| E::Fr::from_str("2").unwrap().pow(&[u64::from(i)]))
+            .collect::<Vec<_>>();
+
+        let pp = |s: &mut String, lc: &LinearCombination<E>| {
+            write!(s, "(").unwrap();
+            let mut is_first = true;
+            for (var, coeff) in proc_lc::<E>(lc.as_ref()) {
+                if coeff == negone {
+                    write!(s, " - ").unwrap();
+                } else if !is_first {
+                    write!(s, " + ").unwrap();
+                }
+                is_first = false;
+
+                if coeff != E::Fr::one() && coeff != negone {
+                    for (i, x) in powers_of_two.iter().enumerate() {
+                        if x == &coeff {
+                            write!(s, "2^{} . ", i).unwrap();
+                            break;
+                        }
+                    }
+
+                    write!(s, "{} . ", coeff).unwrap();
+                }
+
+                match var.0.get_unchecked() {
+                    Index::Input(i) => {
+                        write!(s, "`{}`", &self.inputs[i].1).unwrap();
+                    }
+                    Index::Aux(i) => {
+                        write!(s, "`{}`", &self.aux[i].1).unwrap();
+                    }
+                }
+            }
+            if is_first {
+                // Nothing was visited, print 0.
+                write!(s, "0").unwrap();
+            }
+            write!(s, ")").unwrap();
+        };
+
+        for &(ref a, ref b, ref c, ref name) in &self.constraints {
+            write!(&mut s, "\n").unwrap();
+
+            write!(&mut s, "{}: ", name).unwrap();
+            pp(&mut s, a);
+            write!(&mut s, " * ").unwrap();
+            pp(&mut s, b);
+            write!(&mut s, " = ").unwrap();
+            pp(&mut s, c);
+        }
+
+        write!(&mut s, "\n").unwrap();
+
+        s
+    }
+
+    pub fn hash(&self) -> String {
+        let mut h = Blake2sParams::new().hash_length(32).to_state();
+        {
+            let mut buf = [0u8; 24];
+
+            BigEndian::write_u64(&mut buf[0..8], self.inputs.len() as u64);
+            BigEndian::write_u64(&mut buf[8..16], self.aux.len() as u64);
+            BigEndian::write_u64(&mut buf[16..24], self.constraints.len() as u64);
+            h.update(&buf);
+        }
+
+        for constraint in &self.constraints {
+            hash_lc::<E>(constraint.0.as_ref(), &mut h);
+            hash_lc::<E>(constraint.1.as_ref(), &mut h);
+            hash_lc::<E>(constraint.2.as_ref(), &mut h);
+        }
+
+        let mut s = String::new();
+        for b in h.finalize().as_ref() {
+            s += &format!("{:02x}", b);
+        }
+
+        s
+    }
+
+    pub fn which_is_unsatisfied(&self) -> Option<&str> {
+        for &(ref a, ref b, ref c, ref path) in &self.constraints {
+            let mut a = eval_lc::<E>(a.as_ref(), &self.inputs, &self.aux);
+            let b = eval_lc::<E>(b.as_ref(), &self.inputs, &self.aux);
+            let c = eval_lc::<E>(c.as_ref(), &self.inputs, &self.aux);
+
+            a.mul_assign(&b);
+
+            if a != c {
+                return Some(&*path);
+            }
+        }
+
+        None
+    }
+
+    pub fn is_satisfied(&self) -> bool {
+        self.which_is_unsatisfied().is_none()
+    }
+
+    pub fn num_constraints(&self) -> usize {
+        self.constraints.len()
+    }
+
+    pub fn set(&mut self, path: &str, to: E::Fr) {
+        match self.named_objects.get(path) {
+            Some(&NamedObject::Var(ref v)) => match v.get_unchecked() {
+                Index::Input(index) => self.inputs[index].0 = to,
+                Index::Aux(index) => self.aux[index].0 = to,
+            },
+            Some(e) => panic!(
+                "tried to set path `{}` to value, but `{:?}` already exists there.",
+                path, e
+            ),
+            _ => panic!("no variable exists at path: {}", path),
+        }
+    }
+
+    pub fn verify(&self, expected: &[E::Fr]) -> bool {
+        assert_eq!(expected.len() + 1, self.inputs.len());
+
+        for (a, b) in self.inputs.iter().skip(1).zip(expected.iter()) {
+            if &a.0 != b {
+                return false;
+            }
+        }
+
+        true
+    }
+
+    pub fn num_inputs(&self) -> usize {
+        self.inputs.len()
+    }
+
+    pub fn get_input(&mut self, index: usize, path: &str) -> E::Fr {
+        let (assignment, name) = self.inputs[index].clone();
+
+        assert_eq!(path, name);
+
+        assignment
+    }
+
+    pub fn get(&mut self, path: &str) -> E::Fr {
+        match self.named_objects.get(path) {
+            Some(&NamedObject::Var(ref v)) => match v.get_unchecked() {
+                Index::Input(index) => self.inputs[index].0,
+                Index::Aux(index) => self.aux[index].0,
+            },
+            Some(e) => panic!(
+                "tried to get value of path `{}`, but `{:?}` exists there (not a variable)",
+                path, e
+            ),
+            _ => panic!("no variable exists at path: {}", path),
+        }
+    }
+
+    fn set_named_obj(&mut self, path: String, to: NamedObject) {
+        if self.named_objects.contains_key(&path) {
+            panic!("tried to create object at existing path: {}", path);
+        }
+
+        self.named_objects.insert(path, to);
+    }
+}
+
+fn compute_path(ns: &[String], this: String) -> String {
+    if this.chars().any(|a| a == '/') {
+        panic!("'/' is not allowed in names");
+    }
+
+    let mut name = String::new();
+
+    let mut needs_separation = false;
+    for ns in ns.iter().chain(Some(&this).into_iter()) {
+        if needs_separation {
+            name += "/";
+        }
+
+        name += ns;
+        needs_separation = true;
+    }
+
+    name
+}
+
+impl<E: ScalarEngine> ConstraintSystem<E> for TestConstraintSystem<E> {
+    type Root = Self;
+
+    fn alloc<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        let index = self.aux.len();
+        let path = compute_path(&self.current_namespace, annotation().into());
+        self.aux.push((f()?, path.clone()));
+        let var = Variable::new_unchecked(Index::Aux(index));
+        self.set_named_obj(path, NamedObject::Var(var));
+
+        Ok(var)
+    }
+
+    fn alloc_input<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        let index = self.inputs.len();
+        let path = compute_path(&self.current_namespace, annotation().into());
+        self.inputs.push((f()?, path.clone()));
+        let var = Variable::new_unchecked(Index::Input(index));
+        self.set_named_obj(path, NamedObject::Var(var));
+
+        Ok(var)
+    }
+
+    fn enforce<A, AR, LA, LB, LC>(&mut self, annotation: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+    {
+        let path = compute_path(&self.current_namespace, annotation().into());
+        let index = self.constraints.len();
+        self.set_named_obj(path.clone(), NamedObject::Constraint(index));
+
+        let a = a(LinearCombination::zero());
+        let b = b(LinearCombination::zero());
+        let c = c(LinearCombination::zero());
+
+        self.constraints.push((a, b, c, path));
+    }
+
+    fn push_namespace<NR, N>(&mut self, name_fn: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        let name = name_fn().into();
+        let path = compute_path(&self.current_namespace, name.clone());
+        self.set_named_obj(path.clone(), NamedObject::Namespace);
+        self.current_namespace.push(name);
+    }
+
+    fn pop_namespace(&mut self) {
+        assert!(self.current_namespace.pop().is_some());
+    }
+
+    fn get_root(&mut self) -> &mut Self::Root {
+        self
+    }
+}
+
+#[test]
+fn test_cs() {
+    use ff::PrimeField;
+    use pairing::bls12_381::{Bls12, Fr};
+
+    let mut cs = TestConstraintSystem::<Bls12>::new();
+    assert!(cs.is_satisfied());
+    assert_eq!(cs.num_constraints(), 0);
+    let a = cs
+        .namespace(|| "a")
+        .alloc(|| "var", || Ok(Fr::from_str("10").unwrap()))
+        .unwrap();
+    let b = cs
+        .namespace(|| "b")
+        .alloc(|| "var", || Ok(Fr::from_str("4").unwrap()))
+        .unwrap();
+    let c = cs
+        .alloc(|| "product", || Ok(Fr::from_str("40").unwrap()))
+        .unwrap();
+
+    cs.enforce(|| "mult", |lc| lc + a, |lc| lc + b, |lc| lc + c);
+    assert!(cs.is_satisfied());
+    assert_eq!(cs.num_constraints(), 1);
+
+    cs.set("a/var", Fr::from_str("4").unwrap());
+
+    let one = TestConstraintSystem::<Bls12>::one();
+    cs.enforce(|| "eq", |lc| lc + a, |lc| lc + one, |lc| lc + b);
+
+    assert!(!cs.is_satisfied());
+    assert!(cs.which_is_unsatisfied() == Some("mult"));
+
+    assert!(cs.get("product") == Fr::from_str("40").unwrap());
+
+    cs.set("product", Fr::from_str("16").unwrap());
+    assert!(cs.is_satisfied());
+
+    {
+        let mut cs = cs.namespace(|| "test1");
+        let mut cs = cs.namespace(|| "test2");
+        cs.alloc(|| "hehe", || Ok(Fr::one())).unwrap();
+    }
+
+    assert!(cs.get("test1/test2/hehe") == Fr::one());
+}

bellman/src/gadgets/uint32.rs

@@ -0,0 +1,757 @@
+//! Circuit representation of a [`u32`], with helpers for the [`sha256`]
+//! gadgets.
+//!
+//! [`sha256`]: crate::gadgets::sha256
+
+use ff::{Field, PrimeField, ScalarEngine};
+
+use crate::{ConstraintSystem, LinearCombination, SynthesisError};
+
+use super::boolean::{AllocatedBit, Boolean};
+
+use super::multieq::MultiEq;
+
+/// Represents an interpretation of 32 `Boolean` objects as an
+/// unsigned integer.
+#[derive(Clone)]
+pub struct UInt32 {
+    // Least significant bit first
+    bits: Vec<Boolean>,
+    value: Option<u32>,
+}
+
+impl UInt32 {
+    /// Construct a constant `UInt32` from a `u32`
+    pub fn constant(value: u32) -> Self {
+        let mut bits = Vec::with_capacity(32);
+
+        let mut tmp = value;
+        for _ in 0..32 {
+            if tmp & 1 == 1 {
+                bits.push(Boolean::constant(true))
+            } else {
+                bits.push(Boolean::constant(false))
+            }
+
+            tmp >>= 1;
+        }
+
+        UInt32 {
+            bits,
+            value: Some(value),
+        }
+    }
+
+    /// Allocate a `UInt32` in the constraint system
+    pub fn alloc<E, CS>(mut cs: CS, value: Option<u32>) -> Result<Self, SynthesisError>
+    where
+        E: ScalarEngine,
+        CS: ConstraintSystem<E>,
+    {
+        let values = match value {
+            Some(mut val) => {
+                let mut v = Vec::with_capacity(32);
+
+                for _ in 0..32 {
+                    v.push(Some(val & 1 == 1));
+                    val >>= 1;
+                }
+
+                v
+            }
+            None => vec![None; 32],
+        };
+
+        let bits = values
+            .into_iter()
+            .enumerate()
+            .map(|(i, v)| {
+                Ok(Boolean::from(AllocatedBit::alloc(
+                    cs.namespace(|| format!("allocated bit {}", i)),
+                    v,
+                )?))
+            })
+            .collect::<Result<Vec<_>, SynthesisError>>()?;
+
+        Ok(UInt32 { bits, value })
+    }
+
+    pub fn into_bits_be(self) -> Vec<Boolean> {
+        let mut ret = self.bits;
+        ret.reverse();
+        ret
+    }
+
+    pub fn from_bits_be(bits: &[Boolean]) -> Self {
+        assert_eq!(bits.len(), 32);
+
+        let mut value = Some(0u32);
+        for b in bits {
+            value.as_mut().map(|v| *v <<= 1);
+
+            match b.get_value() {
+                Some(true) => {
+                    value.as_mut().map(|v| *v |= 1);
+                }
+                Some(false) => {}
+                None => {
+                    value = None;
+                }
+            }
+        }
+
+        UInt32 {
+            value,
+            bits: bits.iter().rev().cloned().collect(),
+        }
+    }
+
+    /// Turns this `UInt32` into its little-endian byte order representation.
+    pub fn into_bits(self) -> Vec<Boolean> {
+        self.bits
+    }
+
+    /// Converts a little-endian byte order representation of bits into a
+    /// `UInt32`.
+    pub fn from_bits(bits: &[Boolean]) -> Self {
+        assert_eq!(bits.len(), 32);
+
+        let new_bits = bits.to_vec();
+
+        let mut value = Some(0u32);
+        for b in new_bits.iter().rev() {
+            value.as_mut().map(|v| *v <<= 1);
+
+            match *b {
+                Boolean::Constant(b) => {
+                    if b {
+                        value.as_mut().map(|v| *v |= 1);
+                    }
+                }
+                Boolean::Is(ref b) => match b.get_value() {
+                    Some(true) => {
+                        value.as_mut().map(|v| *v |= 1);
+                    }
+                    Some(false) => {}
+                    None => value = None,
+                },
+                Boolean::Not(ref b) => match b.get_value() {
+                    Some(false) => {
+                        value.as_mut().map(|v| *v |= 1);
+                    }
+                    Some(true) => {}
+                    None => value = None,
+                },
+            }
+        }
+
+        UInt32 {
+            value,
+            bits: new_bits,
+        }
+    }
+
+    pub fn rotr(&self, by: usize) -> Self {
+        let by = by % 32;
+
+        let new_bits = self
+            .bits
+            .iter()
+            .skip(by)
+            .chain(self.bits.iter())
+            .take(32)
+            .cloned()
+            .collect();
+
+        UInt32 {
+            bits: new_bits,
+            value: self.value.map(|v| v.rotate_right(by as u32)),
+        }
+    }
+
+    pub fn shr(&self, by: usize) -> Self {
+        let by = by % 32;
+
+        let fill = Boolean::constant(false);
+
+        let new_bits = self
+            .bits
+            .iter() // The bits are least significant first
+            .skip(by) // Skip the bits that will be lost during the shift
+            .chain(Some(&fill).into_iter().cycle()) // Rest will be zeros
+            .take(32) // Only 32 bits needed!
+            .cloned()
+            .collect();
+
+        UInt32 {
+            bits: new_bits,
+            value: self.value.map(|v| v >> by as u32),
+        }
+    }
+
+    fn triop<E, CS, F, U>(
+        mut cs: CS,
+        a: &Self,
+        b: &Self,
+        c: &Self,
+        tri_fn: F,
+        circuit_fn: U,
+    ) -> Result<Self, SynthesisError>
+    where
+        E: ScalarEngine,
+        CS: ConstraintSystem<E>,
+        F: Fn(u32, u32, u32) -> u32,
+        U: Fn(&mut CS, usize, &Boolean, &Boolean, &Boolean) -> Result<Boolean, SynthesisError>,
+    {
+        let new_value = match (a.value, b.value, c.value) {
+            (Some(a), Some(b), Some(c)) => Some(tri_fn(a, b, c)),
+            _ => None,
+        };
+
+        let bits = a
+            .bits
+            .iter()
+            .zip(b.bits.iter())
+            .zip(c.bits.iter())
+            .enumerate()
+            .map(|(i, ((a, b), c))| circuit_fn(&mut cs, i, a, b, c))
+            .collect::<Result<_, _>>()?;
+
+        Ok(UInt32 {
+            bits,
+            value: new_value,
+        })
+    }
+
+    /// Compute the `maj` value (a and b) xor (a and c) xor (b and c)
+    /// during SHA256.
+    pub fn sha256_maj<E, CS>(cs: CS, a: &Self, b: &Self, c: &Self) -> Result<Self, SynthesisError>
+    where
+        E: ScalarEngine,
+        CS: ConstraintSystem<E>,
+    {
+        Self::triop(
+            cs,
+            a,
+            b,
+            c,
+            |a, b, c| (a & b) ^ (a & c) ^ (b & c),
+            |cs, i, a, b, c| Boolean::sha256_maj(cs.namespace(|| format!("maj {}", i)), a, b, c),
+        )
+    }
+
+    /// Compute the `ch` value `(a and b) xor ((not a) and c)`
+    /// during SHA256.
+    pub fn sha256_ch<E, CS>(cs: CS, a: &Self, b: &Self, c: &Self) -> Result<Self, SynthesisError>
+    where
+        E: ScalarEngine,
+        CS: ConstraintSystem<E>,
+    {
+        Self::triop(
+            cs,
+            a,
+            b,
+            c,
+            |a, b, c| (a & b) ^ ((!a) & c),
+            |cs, i, a, b, c| Boolean::sha256_ch(cs.namespace(|| format!("ch {}", i)), a, b, c),
+        )
+    }
+
+    /// XOR this `UInt32` with another `UInt32`
+    pub fn xor<E, CS>(&self, mut cs: CS, other: &Self) -> Result<Self, SynthesisError>
+    where
+        E: ScalarEngine,
+        CS: ConstraintSystem<E>,
+    {
+        let new_value = match (self.value, other.value) {
+            (Some(a), Some(b)) => Some(a ^ b),
+            _ => None,
+        };
+
+        let bits = self
+            .bits
+            .iter()
+            .zip(other.bits.iter())
+            .enumerate()
+            .map(|(i, (a, b))| Boolean::xor(cs.namespace(|| format!("xor of bit {}", i)), a, b))
+            .collect::<Result<_, _>>()?;
+
+        Ok(UInt32 {
+            bits,
+            value: new_value,
+        })
+    }
+
+    /// Perform modular addition of several `UInt32` objects.
+    pub fn addmany<E, CS, M>(mut cs: M, operands: &[Self]) -> Result<Self, SynthesisError>
+    where
+        E: ScalarEngine,
+        CS: ConstraintSystem<E>,
+        M: ConstraintSystem<E, Root = MultiEq<E, CS>>,
+    {
+        // Make some arbitrary bounds for ourselves to avoid overflows
+        // in the scalar field
+        assert!(E::Fr::NUM_BITS >= 64);
+        assert!(operands.len() >= 2); // Weird trivial cases that should never happen
+        assert!(operands.len() <= 10);
+
+        // Compute the maximum value of the sum so we allocate enough bits for
+        // the result
+        let mut max_value = (operands.len() as u64) * (u64::from(u32::max_value()));
+
+        // Keep track of the resulting value
+        let mut result_value = Some(0u64);
+
+        // This is a linear combination that we will enforce to equal the
+        // output
+        let mut lc = LinearCombination::zero();
+
+        let mut all_constants = true;
+
+        // Iterate over the operands
+        for op in operands {
+            // Accumulate the value
+            match op.value {
+                Some(val) => {
+                    result_value.as_mut().map(|v| *v += u64::from(val));
+                }
+                None => {
+                    // If any of our operands have unknown value, we won't
+                    // know the value of the result
+                    result_value = None;
+                }
+            }
+
+            // Iterate over each bit of the operand and add the operand to
+            // the linear combination
+            let mut coeff = E::Fr::one();
+            for bit in &op.bits {
+                lc = lc + &bit.lc(CS::one(), coeff);
+
+                all_constants &= bit.is_constant();
+
+                coeff.double();
+            }
+        }
+
+        // The value of the actual result is modulo 2^32
+        let modular_value = result_value.map(|v| v as u32);
+
+        if all_constants && modular_value.is_some() {
+            // We can just return a constant, rather than
+            // unpacking the result into allocated bits.
+
+            return Ok(UInt32::constant(modular_value.unwrap()));
+        }
+
+        // Storage area for the resulting bits
+        let mut result_bits = vec![];
+
+        // Linear combination representing the output,
+        // for comparison with the sum of the operands
+        let mut result_lc = LinearCombination::zero();
+
+        // Allocate each bit of the result
+        let mut coeff = E::Fr::one();
+        let mut i = 0;
+        while max_value != 0 {
+            // Allocate the bit
+            let b = AllocatedBit::alloc(
+                cs.namespace(|| format!("result bit {}", i)),
+                result_value.map(|v| (v >> i) & 1 == 1),
+            )?;
+
+            // Add this bit to the result combination
+            result_lc = result_lc + (coeff, b.get_variable());
+
+            result_bits.push(b.into());
+
+            max_value >>= 1;
+            i += 1;
+            coeff.double();
+        }
+
+        // Enforce equality between the sum and result
+        cs.get_root().enforce_equal(i, &lc, &result_lc);
+
+        // Discard carry bits that we don't care about
+        result_bits.truncate(32);
+
+        Ok(UInt32 {
+            bits: result_bits,
+            value: modular_value,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::UInt32;
+    use crate::gadgets::boolean::Boolean;
+    use crate::gadgets::multieq::MultiEq;
+    use crate::gadgets::test::*;
+    use crate::ConstraintSystem;
+    use ff::Field;
+    use pairing::bls12_381::Bls12;
+    use rand_core::{RngCore, SeedableRng};
+    use rand_xorshift::XorShiftRng;
+
+    #[test]
+    fn test_uint32_from_bits_be() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let v = (0..32)
+                .map(|_| Boolean::constant(rng.next_u32() % 2 != 0))
+                .collect::<Vec<_>>();
+
+            let b = UInt32::from_bits_be(&v);
+
+            for (i, bit) in b.bits.iter().enumerate() {
+                match *bit {
+                    Boolean::Constant(bit) => {
+                        assert!(bit == ((b.value.unwrap() >> i) & 1 == 1));
+                    }
+                    _ => unreachable!(),
+                }
+            }
+
+            let expected_to_be_same = b.into_bits_be();
+
+            for x in v.iter().zip(expected_to_be_same.iter()) {
+                match x {
+                    (&Boolean::Constant(true), &Boolean::Constant(true)) => {}
+                    (&Boolean::Constant(false), &Boolean::Constant(false)) => {}
+                    _ => unreachable!(),
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_uint32_from_bits() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let v = (0..32)
+                .map(|_| Boolean::constant(rng.next_u32() % 2 != 0))
+                .collect::<Vec<_>>();
+
+            let b = UInt32::from_bits(&v);
+
+            for (i, bit) in b.bits.iter().enumerate() {
+                match *bit {
+                    Boolean::Constant(bit) => {
+                        assert!(bit == ((b.value.unwrap() >> i) & 1 == 1));
+                    }
+                    _ => unreachable!(),
+                }
+            }
+
+            let expected_to_be_same = b.into_bits();
+
+            for x in v.iter().zip(expected_to_be_same.iter()) {
+                match x {
+                    (&Boolean::Constant(true), &Boolean::Constant(true)) => {}
+                    (&Boolean::Constant(false), &Boolean::Constant(false)) => {}
+                    _ => unreachable!(),
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_uint32_xor() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = rng.next_u32();
+            let b = rng.next_u32();
+            let c = rng.next_u32();
+
+            let mut expected = a ^ b ^ c;
+
+            let a_bit = UInt32::alloc(cs.namespace(|| "a_bit"), Some(a)).unwrap();
+            let b_bit = UInt32::constant(b);
+            let c_bit = UInt32::alloc(cs.namespace(|| "c_bit"), Some(c)).unwrap();
+
+            let r = a_bit.xor(cs.namespace(|| "first xor"), &b_bit).unwrap();
+            let r = r.xor(cs.namespace(|| "second xor"), &c_bit).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            assert!(r.value == Some(expected));
+
+            for b in r.bits.iter() {
+                match *b {
+                    Boolean::Is(ref b) => {
+                        assert!(b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    Boolean::Not(ref b) => {
+                        assert!(!b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    Boolean::Constant(b) => {
+                        assert!(b == (expected & 1 == 1));
+                    }
+                }
+
+                expected >>= 1;
+            }
+        }
+    }
+
+    #[test]
+    fn test_uint32_addmany_constants() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = rng.next_u32();
+            let b = rng.next_u32();
+            let c = rng.next_u32();
+
+            let a_bit = UInt32::constant(a);
+            let b_bit = UInt32::constant(b);
+            let c_bit = UInt32::constant(c);
+
+            let mut expected = a.wrapping_add(b).wrapping_add(c);
+
+            let r = {
+                let mut cs = MultiEq::new(&mut cs);
+                let r =
+                    UInt32::addmany(cs.namespace(|| "addition"), &[a_bit, b_bit, c_bit]).unwrap();
+                r
+            };
+
+            assert!(r.value == Some(expected));
+
+            for b in r.bits.iter() {
+                match *b {
+                    Boolean::Is(_) => panic!(),
+                    Boolean::Not(_) => panic!(),
+                    Boolean::Constant(b) => {
+                        assert!(b == (expected & 1 == 1));
+                    }
+                }
+
+                expected >>= 1;
+            }
+        }
+    }
+
+    #[test]
+    fn test_uint32_addmany() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = rng.next_u32();
+            let b = rng.next_u32();
+            let c = rng.next_u32();
+            let d = rng.next_u32();
+
+            let mut expected = (a ^ b).wrapping_add(c).wrapping_add(d);
+
+            let a_bit = UInt32::alloc(cs.namespace(|| "a_bit"), Some(a)).unwrap();
+            let b_bit = UInt32::constant(b);
+            let c_bit = UInt32::constant(c);
+            let d_bit = UInt32::alloc(cs.namespace(|| "d_bit"), Some(d)).unwrap();
+
+            let r = a_bit.xor(cs.namespace(|| "xor"), &b_bit).unwrap();
+            let r = {
+                let mut cs = MultiEq::new(&mut cs);
+                UInt32::addmany(cs.namespace(|| "addition"), &[r, c_bit, d_bit]).unwrap()
+            };
+
+            assert!(cs.is_satisfied());
+
+            assert!(r.value == Some(expected));
+
+            for b in r.bits.iter() {
+                match *b {
+                    Boolean::Is(ref b) => {
+                        assert!(b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    Boolean::Not(ref b) => {
+                        assert!(!b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    Boolean::Constant(_) => unreachable!(),
+                }
+
+                expected >>= 1;
+            }
+
+            // Flip a bit and see if the addition constraint still works
+            if cs.get("addition/result bit 0/boolean").is_zero() {
+                cs.set("addition/result bit 0/boolean", Field::one());
+            } else {
+                cs.set("addition/result bit 0/boolean", Field::zero());
+            }
+
+            assert!(!cs.is_satisfied());
+        }
+    }
+
+    #[test]
+    fn test_uint32_rotr() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let mut num = rng.next_u32();
+
+        let a = UInt32::constant(num);
+
+        for i in 0..32 {
+            let b = a.rotr(i);
+            assert_eq!(a.bits.len(), b.bits.len());
+
+            assert!(b.value.unwrap() == num);
+
+            let mut tmp = num;
+            for b in &b.bits {
+                match *b {
+                    Boolean::Constant(b) => {
+                        assert_eq!(b, tmp & 1 == 1);
+                    }
+                    _ => unreachable!(),
+                }
+
+                tmp >>= 1;
+            }
+
+            num = num.rotate_right(1);
+        }
+    }
+
+    #[test]
+    fn test_uint32_shr() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..50 {
+            for i in 0..60 {
+                let num = rng.next_u32();
+                let a = UInt32::constant(num).shr(i);
+                let b = UInt32::constant(num.wrapping_shr(i as u32));
+
+                assert_eq!(a.value.unwrap(), num.wrapping_shr(i as u32));
+
+                assert_eq!(a.bits.len(), b.bits.len());
+                for (a, b) in a.bits.iter().zip(b.bits.iter()) {
+                    assert_eq!(a.get_value().unwrap(), b.get_value().unwrap());
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn test_uint32_sha256_maj() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = rng.next_u32();
+            let b = rng.next_u32();
+            let c = rng.next_u32();
+
+            let mut expected = (a & b) ^ (a & c) ^ (b & c);
+
+            let a_bit = UInt32::alloc(cs.namespace(|| "a_bit"), Some(a)).unwrap();
+            let b_bit = UInt32::constant(b);
+            let c_bit = UInt32::alloc(cs.namespace(|| "c_bit"), Some(c)).unwrap();
+
+            let r = UInt32::sha256_maj(&mut cs, &a_bit, &b_bit, &c_bit).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            assert!(r.value == Some(expected));
+
+            for b in r.bits.iter() {
+                match b {
+                    &Boolean::Is(ref b) => {
+                        assert!(b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    &Boolean::Not(ref b) => {
+                        assert!(!b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    &Boolean::Constant(b) => {
+                        assert!(b == (expected & 1 == 1));
+                    }
+                }
+
+                expected >>= 1;
+            }
+        }
+    }
+
+    #[test]
+    fn test_uint32_sha256_ch() {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a = rng.next_u32();
+            let b = rng.next_u32();
+            let c = rng.next_u32();
+
+            let mut expected = (a & b) ^ ((!a) & c);
+
+            let a_bit = UInt32::alloc(cs.namespace(|| "a_bit"), Some(a)).unwrap();
+            let b_bit = UInt32::constant(b);
+            let c_bit = UInt32::alloc(cs.namespace(|| "c_bit"), Some(c)).unwrap();
+
+            let r = UInt32::sha256_ch(&mut cs, &a_bit, &b_bit, &c_bit).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            assert!(r.value == Some(expected));
+
+            for b in r.bits.iter() {
+                match b {
+                    &Boolean::Is(ref b) => {
+                        assert!(b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    &Boolean::Not(ref b) => {
+                        assert!(!b.get_value().unwrap() == (expected & 1 == 1));
+                    }
+                    &Boolean::Constant(b) => {
+                        assert!(b == (expected & 1 == 1));
+                    }
+                }
+
+                expected >>= 1;
+            }
+        }
+    }
+}

bellman/src/groth16/generator.rs

@@ -0,0 +1,478 @@
+use rand_core::RngCore;
+
+use std::sync::Arc;
+
+use ff::{Field, PrimeField};
+use group::{CurveAffine, CurveProjective, Wnaf};
+use pairing::Engine;
+
+use super::{Parameters, VerifyingKey};
+
+use crate::{Circuit, ConstraintSystem, Index, LinearCombination, SynthesisError, Variable};
+
+use crate::domain::{EvaluationDomain, Scalar};
+
+use crate::multicore::Worker;
+
+/// Generates a random common reference string for
+/// a circuit.
+pub fn generate_random_parameters<E, C, R>(
+    circuit: C,
+    rng: &mut R,
+) -> Result<Parameters<E>, SynthesisError>
+where
+    E: Engine,
+    C: Circuit<E>,
+    R: RngCore,
+{
+    let g1 = E::G1::random(rng);
+    let g2 = E::G2::random(rng);
+    let alpha = E::Fr::random(rng);
+    let beta = E::Fr::random(rng);
+    let gamma = E::Fr::random(rng);
+    let delta = E::Fr::random(rng);
+    let tau = E::Fr::random(rng);
+
+    generate_parameters::<E, C>(circuit, g1, g2, alpha, beta, gamma, delta, tau)
+}
+
+/// This is our assembly structure that we'll use to synthesize the
+/// circuit into a QAP.
+struct KeypairAssembly<E: Engine> {
+    num_inputs: usize,
+    num_aux: usize,
+    num_constraints: usize,
+    at_inputs: Vec<Vec<(E::Fr, usize)>>,
+    bt_inputs: Vec<Vec<(E::Fr, usize)>>,
+    ct_inputs: Vec<Vec<(E::Fr, usize)>>,
+    at_aux: Vec<Vec<(E::Fr, usize)>>,
+    bt_aux: Vec<Vec<(E::Fr, usize)>>,
+    ct_aux: Vec<Vec<(E::Fr, usize)>>,
+}
+
+impl<E: Engine> ConstraintSystem<E> for KeypairAssembly<E> {
+    type Root = Self;
+
+    fn alloc<F, A, AR>(&mut self, _: A, _: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        // There is no assignment, so we don't even invoke the
+        // function for obtaining one.
+
+        let index = self.num_aux;
+        self.num_aux += 1;
+
+        self.at_aux.push(vec![]);
+        self.bt_aux.push(vec![]);
+        self.ct_aux.push(vec![]);
+
+        Ok(Variable(Index::Aux(index)))
+    }
+
+    fn alloc_input<F, A, AR>(&mut self, _: A, _: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        // There is no assignment, so we don't even invoke the
+        // function for obtaining one.
+
+        let index = self.num_inputs;
+        self.num_inputs += 1;
+
+        self.at_inputs.push(vec![]);
+        self.bt_inputs.push(vec![]);
+        self.ct_inputs.push(vec![]);
+
+        Ok(Variable(Index::Input(index)))
+    }
+
+    fn enforce<A, AR, LA, LB, LC>(&mut self, _: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+    {
+        fn eval<E: Engine>(
+            l: LinearCombination<E>,
+            inputs: &mut [Vec<(E::Fr, usize)>],
+            aux: &mut [Vec<(E::Fr, usize)>],
+            this_constraint: usize,
+        ) {
+            for (index, coeff) in l.0 {
+                match index {
+                    Variable(Index::Input(id)) => inputs[id].push((coeff, this_constraint)),
+                    Variable(Index::Aux(id)) => aux[id].push((coeff, this_constraint)),
+                }
+            }
+        }
+
+        eval(
+            a(LinearCombination::zero()),
+            &mut self.at_inputs,
+            &mut self.at_aux,
+            self.num_constraints,
+        );
+        eval(
+            b(LinearCombination::zero()),
+            &mut self.bt_inputs,
+            &mut self.bt_aux,
+            self.num_constraints,
+        );
+        eval(
+            c(LinearCombination::zero()),
+            &mut self.ct_inputs,
+            &mut self.ct_aux,
+            self.num_constraints,
+        );
+
+        self.num_constraints += 1;
+    }
+
+    fn push_namespace<NR, N>(&mut self, _: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        // Do nothing; we don't care about namespaces in this context.
+    }
+
+    fn pop_namespace(&mut self) {
+        // Do nothing; we don't care about namespaces in this context.
+    }
+
+    fn get_root(&mut self) -> &mut Self::Root {
+        self
+    }
+}
+
+/// Create parameters for a circuit, given some toxic waste.
+pub fn generate_parameters<E, C>(
+    circuit: C,
+    g1: E::G1,
+    g2: E::G2,
+    alpha: E::Fr,
+    beta: E::Fr,
+    gamma: E::Fr,
+    delta: E::Fr,
+    tau: E::Fr,
+) -> Result<Parameters<E>, SynthesisError>
+where
+    E: Engine,
+    C: Circuit<E>,
+{
+    let mut assembly = KeypairAssembly {
+        num_inputs: 0,
+        num_aux: 0,
+        num_constraints: 0,
+        at_inputs: vec![],
+        bt_inputs: vec![],
+        ct_inputs: vec![],
+        at_aux: vec![],
+        bt_aux: vec![],
+        ct_aux: vec![],
+    };
+
+    // Allocate the "one" input variable
+    assembly.alloc_input(|| "", || Ok(E::Fr::one()))?;
+
+    // Synthesize the circuit.
+    circuit.synthesize(&mut assembly)?;
+
+    // Input constraints to ensure full density of IC query
+    // x * 0 = 0
+    for i in 0..assembly.num_inputs {
+        assembly.enforce(|| "", |lc| lc + Variable(Index::Input(i)), |lc| lc, |lc| lc);
+    }
+
+    // Create bases for blind evaluation of polynomials at tau
+    let powers_of_tau = vec![Scalar::<E>(E::Fr::zero()); assembly.num_constraints];
+    let mut powers_of_tau = EvaluationDomain::from_coeffs(powers_of_tau)?;
+
+    // Compute G1 window table
+    let mut g1_wnaf = Wnaf::new();
+    let g1_wnaf = g1_wnaf.base(g1, {
+        // H query
+        (powers_of_tau.as_ref().len() - 1)
+        // IC/L queries
+        + assembly.num_inputs + assembly.num_aux
+        // A query
+        + assembly.num_inputs + assembly.num_aux
+        // B query
+        + assembly.num_inputs + assembly.num_aux
+    });
+
+    // Compute G2 window table
+    let mut g2_wnaf = Wnaf::new();
+    let g2_wnaf = g2_wnaf.base(g2, {
+        // B query
+        assembly.num_inputs + assembly.num_aux
+    });
+
+    let gamma_inverse = gamma.inverse().ok_or(SynthesisError::UnexpectedIdentity)?;
+    let delta_inverse = delta.inverse().ok_or(SynthesisError::UnexpectedIdentity)?;
+
+    let worker = Worker::new();
+
+    let mut h = vec![E::G1::zero(); powers_of_tau.as_ref().len() - 1];
+    {
+        // Compute powers of tau
+        {
+            let powers_of_tau = powers_of_tau.as_mut();
+            worker.scope(powers_of_tau.len(), |scope, chunk| {
+                for (i, powers_of_tau) in powers_of_tau.chunks_mut(chunk).enumerate() {
+                    scope.spawn(move |_scope| {
+                        let mut current_tau_power = tau.pow(&[(i * chunk) as u64]);
+
+                        for p in powers_of_tau {
+                            p.0 = current_tau_power;
+                            current_tau_power.mul_assign(&tau);
+                        }
+                    });
+                }
+            });
+        }
+
+        // coeff = t(x) / delta
+        let mut coeff = powers_of_tau.z(&tau);
+        coeff.mul_assign(&delta_inverse);
+
+        // Compute the H query with multiple threads
+        worker.scope(h.len(), |scope, chunk| {
+            for (h, p) in h
+                .chunks_mut(chunk)
+                .zip(powers_of_tau.as_ref().chunks(chunk))
+            {
+                let mut g1_wnaf = g1_wnaf.shared();
+
+                scope.spawn(move |_scope| {
+                    // Set values of the H query to g1^{(tau^i * t(tau)) / delta}
+                    for (h, p) in h.iter_mut().zip(p.iter()) {
+                        // Compute final exponent
+                        let mut exp = p.0;
+                        exp.mul_assign(&coeff);
+
+                        // Exponentiate
+                        *h = g1_wnaf.scalar(exp.into_repr());
+                    }
+
+                    // Batch normalize
+                    E::G1::batch_normalization(h);
+                });
+            }
+        });
+    }
+
+    // Use inverse FFT to convert powers of tau to Lagrange coefficients
+    powers_of_tau.ifft(&worker);
+    let powers_of_tau = powers_of_tau.into_coeffs();
+
+    let mut a = vec![E::G1::zero(); assembly.num_inputs + assembly.num_aux];
+    let mut b_g1 = vec![E::G1::zero(); assembly.num_inputs + assembly.num_aux];
+    let mut b_g2 = vec![E::G2::zero(); assembly.num_inputs + assembly.num_aux];
+    let mut ic = vec![E::G1::zero(); assembly.num_inputs];
+    let mut l = vec![E::G1::zero(); assembly.num_aux];
+
+    fn eval<E: Engine>(
+        // wNAF window tables
+        g1_wnaf: &Wnaf<usize, &[E::G1], &mut Vec<i64>>,
+        g2_wnaf: &Wnaf<usize, &[E::G2], &mut Vec<i64>>,
+
+        // Lagrange coefficients for tau
+        powers_of_tau: &[Scalar<E>],
+
+        // QAP polynomials
+        at: &[Vec<(E::Fr, usize)>],
+        bt: &[Vec<(E::Fr, usize)>],
+        ct: &[Vec<(E::Fr, usize)>],
+
+        // Resulting evaluated QAP polynomials
+        a: &mut [E::G1],
+        b_g1: &mut [E::G1],
+        b_g2: &mut [E::G2],
+        ext: &mut [E::G1],
+
+        // Inverse coefficient for ext elements
+        inv: &E::Fr,
+
+        // Trapdoors
+        alpha: &E::Fr,
+        beta: &E::Fr,
+
+        // Worker
+        worker: &Worker,
+    ) {
+        // Sanity check
+        assert_eq!(a.len(), at.len());
+        assert_eq!(a.len(), bt.len());
+        assert_eq!(a.len(), ct.len());
+        assert_eq!(a.len(), b_g1.len());
+        assert_eq!(a.len(), b_g2.len());
+        assert_eq!(a.len(), ext.len());
+
+        // Evaluate polynomials in multiple threads
+        worker.scope(a.len(), |scope, chunk| {
+            for ((((((a, b_g1), b_g2), ext), at), bt), ct) in a
+                .chunks_mut(chunk)
+                .zip(b_g1.chunks_mut(chunk))
+                .zip(b_g2.chunks_mut(chunk))
+                .zip(ext.chunks_mut(chunk))
+                .zip(at.chunks(chunk))
+                .zip(bt.chunks(chunk))
+                .zip(ct.chunks(chunk))
+            {
+                let mut g1_wnaf = g1_wnaf.shared();
+                let mut g2_wnaf = g2_wnaf.shared();
+
+                scope.spawn(move |_scope| {
+                    for ((((((a, b_g1), b_g2), ext), at), bt), ct) in a
+                        .iter_mut()
+                        .zip(b_g1.iter_mut())
+                        .zip(b_g2.iter_mut())
+                        .zip(ext.iter_mut())
+                        .zip(at.iter())
+                        .zip(bt.iter())
+                        .zip(ct.iter())
+                    {
+                        fn eval_at_tau<E: Engine>(
+                            powers_of_tau: &[Scalar<E>],
+                            p: &[(E::Fr, usize)],
+                        ) -> E::Fr {
+                            let mut acc = E::Fr::zero();
+
+                            for &(ref coeff, index) in p {
+                                let mut n = powers_of_tau[index].0;
+                                n.mul_assign(coeff);
+                                acc.add_assign(&n);
+                            }
+
+                            acc
+                        }
+
+                        // Evaluate QAP polynomials at tau
+                        let mut at = eval_at_tau(powers_of_tau, at);
+                        let mut bt = eval_at_tau(powers_of_tau, bt);
+                        let ct = eval_at_tau(powers_of_tau, ct);
+
+                        // Compute A query (in G1)
+                        if !at.is_zero() {
+                            *a = g1_wnaf.scalar(at.into_repr());
+                        }
+
+                        // Compute B query (in G1/G2)
+                        if !bt.is_zero() {
+                            let bt_repr = bt.into_repr();
+                            *b_g1 = g1_wnaf.scalar(bt_repr);
+                            *b_g2 = g2_wnaf.scalar(bt_repr);
+                        }
+
+                        at.mul_assign(&beta);
+                        bt.mul_assign(&alpha);
+
+                        let mut e = at;
+                        e.add_assign(&bt);
+                        e.add_assign(&ct);
+                        e.mul_assign(inv);
+
+                        *ext = g1_wnaf.scalar(e.into_repr());
+                    }
+
+                    // Batch normalize
+                    E::G1::batch_normalization(a);
+                    E::G1::batch_normalization(b_g1);
+                    E::G2::batch_normalization(b_g2);
+                    E::G1::batch_normalization(ext);
+                });
+            }
+        });
+    }
+
+    // Evaluate for inputs.
+    eval(
+        &g1_wnaf,
+        &g2_wnaf,
+        &powers_of_tau,
+        &assembly.at_inputs,
+        &assembly.bt_inputs,
+        &assembly.ct_inputs,
+        &mut a[0..assembly.num_inputs],
+        &mut b_g1[0..assembly.num_inputs],
+        &mut b_g2[0..assembly.num_inputs],
+        &mut ic,
+        &gamma_inverse,
+        &alpha,
+        &beta,
+        &worker,
+    );
+
+    // Evaluate for auxiliary variables.
+    eval(
+        &g1_wnaf,
+        &g2_wnaf,
+        &powers_of_tau,
+        &assembly.at_aux,
+        &assembly.bt_aux,
+        &assembly.ct_aux,
+        &mut a[assembly.num_inputs..],
+        &mut b_g1[assembly.num_inputs..],
+        &mut b_g2[assembly.num_inputs..],
+        &mut l,
+        &delta_inverse,
+        &alpha,
+        &beta,
+        &worker,
+    );
+
+    // Don't allow any elements be unconstrained, so that
+    // the L query is always fully dense.
+    for e in l.iter() {
+        if e.is_zero() {
+            return Err(SynthesisError::UnconstrainedVariable);
+        }
+    }
+
+    let g1 = g1.into_affine();
+    let g2 = g2.into_affine();
+
+    let vk = VerifyingKey::<E> {
+        alpha_g1: g1.mul(alpha).into_affine(),
+        beta_g1: g1.mul(beta).into_affine(),
+        beta_g2: g2.mul(beta).into_affine(),
+        gamma_g2: g2.mul(gamma).into_affine(),
+        delta_g1: g1.mul(delta).into_affine(),
+        delta_g2: g2.mul(delta).into_affine(),
+        ic: ic.into_iter().map(|e| e.into_affine()).collect(),
+    };
+
+    Ok(Parameters {
+        vk,
+        h: Arc::new(h.into_iter().map(|e| e.into_affine()).collect()),
+        l: Arc::new(l.into_iter().map(|e| e.into_affine()).collect()),
+
+        // Filter points at infinity away from A/B queries
+        a: Arc::new(
+            a.into_iter()
+                .filter(|e| !e.is_zero())
+                .map(|e| e.into_affine())
+                .collect(),
+        ),
+        b_g1: Arc::new(
+            b_g1.into_iter()
+                .filter(|e| !e.is_zero())
+                .map(|e| e.into_affine())
+                .collect(),
+        ),
+        b_g2: Arc::new(
+            b_g2.into_iter()
+                .filter(|e| !e.is_zero())
+                .map(|e| e.into_affine())
+                .collect(),
+        ),
+    })
+}

bellman/src/groth16/mod.rs

@@ -0,0 +1,558 @@
+//! The [Groth16] proving system.
+//!
+//! [Groth16]: https://eprint.iacr.org/2016/260
+
+use group::{CurveAffine, EncodedPoint};
+use pairing::{Engine, PairingCurveAffine};
+
+use crate::SynthesisError;
+
+use crate::multiexp::SourceBuilder;
+use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
+use std::io::{self, Read, Write};
+use std::sync::Arc;
+
+#[cfg(test)]
+mod tests;
+
+mod generator;
+mod prover;
+mod verifier;
+
+pub use self::generator::*;
+pub use self::prover::*;
+pub use self::verifier::*;
+
+#[derive(Clone)]
+pub struct Proof<E: Engine> {
+    pub a: E::G1Affine,
+    pub b: E::G2Affine,
+    pub c: E::G1Affine,
+}
+
+impl<E: Engine> PartialEq for Proof<E> {
+    fn eq(&self, other: &Self) -> bool {
+        self.a == other.a && self.b == other.b && self.c == other.c
+    }
+}
+
+impl<E: Engine> Proof<E> {
+    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
+        writer.write_all(self.a.into_compressed().as_ref())?;
+        writer.write_all(self.b.into_compressed().as_ref())?;
+        writer.write_all(self.c.into_compressed().as_ref())?;
+
+        Ok(())
+    }
+
+    pub fn read<R: Read>(mut reader: R) -> io::Result<Self> {
+        let mut g1_repr = <E::G1Affine as CurveAffine>::Compressed::empty();
+        let mut g2_repr = <E::G2Affine as CurveAffine>::Compressed::empty();
+
+        reader.read_exact(g1_repr.as_mut())?;
+        let a = g1_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+            .and_then(|e| {
+                if e.is_zero() {
+                    Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        "point at infinity",
+                    ))
+                } else {
+                    Ok(e)
+                }
+            })?;
+
+        reader.read_exact(g2_repr.as_mut())?;
+        let b = g2_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+            .and_then(|e| {
+                if e.is_zero() {
+                    Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        "point at infinity",
+                    ))
+                } else {
+                    Ok(e)
+                }
+            })?;
+
+        reader.read_exact(g1_repr.as_mut())?;
+        let c = g1_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+            .and_then(|e| {
+                if e.is_zero() {
+                    Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        "point at infinity",
+                    ))
+                } else {
+                    Ok(e)
+                }
+            })?;
+
+        Ok(Proof { a, b, c })
+    }
+}
+
+#[derive(Clone)]
+pub struct VerifyingKey<E: Engine> {
+    // alpha in g1 for verifying and for creating A/C elements of
+    // proof. Never the point at infinity.
+    pub alpha_g1: E::G1Affine,
+
+    // beta in g1 and g2 for verifying and for creating B/C elements
+    // of proof. Never the point at infinity.
+    pub beta_g1: E::G1Affine,
+    pub beta_g2: E::G2Affine,
+
+    // gamma in g2 for verifying. Never the point at infinity.
+    pub gamma_g2: E::G2Affine,
+
+    // delta in g1/g2 for verifying and proving, essentially the magic
+    // trapdoor that forces the prover to evaluate the C element of the
+    // proof with only components from the CRS. Never the point at
+    // infinity.
+    pub delta_g1: E::G1Affine,
+    pub delta_g2: E::G2Affine,
+
+    // Elements of the form (beta * u_i(tau) + alpha v_i(tau) + w_i(tau)) / gamma
+    // for all public inputs. Because all public inputs have a dummy constraint,
+    // this is the same size as the number of inputs, and never contains points
+    // at infinity.
+    pub ic: Vec<E::G1Affine>,
+}
+
+impl<E: Engine> PartialEq for VerifyingKey<E> {
+    fn eq(&self, other: &Self) -> bool {
+        self.alpha_g1 == other.alpha_g1
+            && self.beta_g1 == other.beta_g1
+            && self.beta_g2 == other.beta_g2
+            && self.gamma_g2 == other.gamma_g2
+            && self.delta_g1 == other.delta_g1
+            && self.delta_g2 == other.delta_g2
+            && self.ic == other.ic
+    }
+}
+
+impl<E: Engine> VerifyingKey<E> {
+    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
+        writer.write_all(self.alpha_g1.into_uncompressed().as_ref())?;
+        writer.write_all(self.beta_g1.into_uncompressed().as_ref())?;
+        writer.write_all(self.beta_g2.into_uncompressed().as_ref())?;
+        writer.write_all(self.gamma_g2.into_uncompressed().as_ref())?;
+        writer.write_all(self.delta_g1.into_uncompressed().as_ref())?;
+        writer.write_all(self.delta_g2.into_uncompressed().as_ref())?;
+        writer.write_u32::<BigEndian>(self.ic.len() as u32)?;
+        for ic in &self.ic {
+            writer.write_all(ic.into_uncompressed().as_ref())?;
+        }
+
+        Ok(())
+    }
+
+    pub fn read<R: Read>(mut reader: R) -> io::Result<Self> {
+        let mut g1_repr = <E::G1Affine as CurveAffine>::Uncompressed::empty();
+        let mut g2_repr = <E::G2Affine as CurveAffine>::Uncompressed::empty();
+
+        reader.read_exact(g1_repr.as_mut())?;
+        let alpha_g1 = g1_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+
+        reader.read_exact(g1_repr.as_mut())?;
+        let beta_g1 = g1_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+
+        reader.read_exact(g2_repr.as_mut())?;
+        let beta_g2 = g2_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+
+        reader.read_exact(g2_repr.as_mut())?;
+        let gamma_g2 = g2_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+
+        reader.read_exact(g1_repr.as_mut())?;
+        let delta_g1 = g1_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+
+        reader.read_exact(g2_repr.as_mut())?;
+        let delta_g2 = g2_repr
+            .into_affine()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+
+        let ic_len = reader.read_u32::<BigEndian>()? as usize;
+
+        let mut ic = vec![];
+
+        for _ in 0..ic_len {
+            reader.read_exact(g1_repr.as_mut())?;
+            let g1 = g1_repr
+                .into_affine()
+                .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+                .and_then(|e| {
+                    if e.is_zero() {
+                        Err(io::Error::new(
+                            io::ErrorKind::InvalidData,
+                            "point at infinity",
+                        ))
+                    } else {
+                        Ok(e)
+                    }
+                })?;
+
+            ic.push(g1);
+        }
+
+        Ok(VerifyingKey {
+            alpha_g1,
+            beta_g1,
+            beta_g2,
+            gamma_g2,
+            delta_g1,
+            delta_g2,
+            ic,
+        })
+    }
+}
+
+#[derive(Clone)]
+pub struct Parameters<E: Engine> {
+    pub vk: VerifyingKey<E>,
+
+    // Elements of the form ((tau^i * t(tau)) / delta) for i between 0 and
+    // m-2 inclusive. Never contains points at infinity.
+    pub h: Arc<Vec<E::G1Affine>>,
+
+    // Elements of the form (beta * u_i(tau) + alpha v_i(tau) + w_i(tau)) / delta
+    // for all auxiliary inputs. Variables can never be unconstrained, so this
+    // never contains points at infinity.
+    pub l: Arc<Vec<E::G1Affine>>,
+
+    // QAP "A" polynomials evaluated at tau in the Lagrange basis. Never contains
+    // points at infinity: polynomials that evaluate to zero are omitted from
+    // the CRS and the prover can deterministically skip their evaluation.
+    pub a: Arc<Vec<E::G1Affine>>,
+
+    // QAP "B" polynomials evaluated at tau in the Lagrange basis. Needed in
+    // G1 and G2 for C/B queries, respectively. Never contains points at
+    // infinity for the same reason as the "A" polynomials.
+    pub b_g1: Arc<Vec<E::G1Affine>>,
+    pub b_g2: Arc<Vec<E::G2Affine>>,
+}
+
+impl<E: Engine> PartialEq for Parameters<E> {
+    fn eq(&self, other: &Self) -> bool {
+        self.vk == other.vk
+            && self.h == other.h
+            && self.l == other.l
+            && self.a == other.a
+            && self.b_g1 == other.b_g1
+            && self.b_g2 == other.b_g2
+    }
+}
+
+impl<E: Engine> Parameters<E> {
+    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
+        self.vk.write(&mut writer)?;
+
+        writer.write_u32::<BigEndian>(self.h.len() as u32)?;
+        for g in &self.h[..] {
+            writer.write_all(g.into_uncompressed().as_ref())?;
+        }
+
+        writer.write_u32::<BigEndian>(self.l.len() as u32)?;
+        for g in &self.l[..] {
+            writer.write_all(g.into_uncompressed().as_ref())?;
+        }
+
+        writer.write_u32::<BigEndian>(self.a.len() as u32)?;
+        for g in &self.a[..] {
+            writer.write_all(g.into_uncompressed().as_ref())?;
+        }
+
+        writer.write_u32::<BigEndian>(self.b_g1.len() as u32)?;
+        for g in &self.b_g1[..] {
+            writer.write_all(g.into_uncompressed().as_ref())?;
+        }
+
+        writer.write_u32::<BigEndian>(self.b_g2.len() as u32)?;
+        for g in &self.b_g2[..] {
+            writer.write_all(g.into_uncompressed().as_ref())?;
+        }
+
+        Ok(())
+    }
+
+    pub fn read<R: Read>(mut reader: R, checked: bool) -> io::Result<Self> {
+        let read_g1 = |reader: &mut R| -> io::Result<E::G1Affine> {
+            let mut repr = <E::G1Affine as CurveAffine>::Uncompressed::empty();
+            reader.read_exact(repr.as_mut())?;
+
+            if checked {
+                repr.into_affine()
+            } else {
+                repr.into_affine_unchecked()
+            }
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+            .and_then(|e| {
+                if e.is_zero() {
+                    Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        "point at infinity",
+                    ))
+                } else {
+                    Ok(e)
+                }
+            })
+        };
+
+        let read_g2 = |reader: &mut R| -> io::Result<E::G2Affine> {
+            let mut repr = <E::G2Affine as CurveAffine>::Uncompressed::empty();
+            reader.read_exact(repr.as_mut())?;
+
+            if checked {
+                repr.into_affine()
+            } else {
+                repr.into_affine_unchecked()
+            }
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+            .and_then(|e| {
+                if e.is_zero() {
+                    Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        "point at infinity",
+                    ))
+                } else {
+                    Ok(e)
+                }
+            })
+        };
+
+        let vk = VerifyingKey::<E>::read(&mut reader)?;
+
+        let mut h = vec![];
+        let mut l = vec![];
+        let mut a = vec![];
+        let mut b_g1 = vec![];
+        let mut b_g2 = vec![];
+
+        {
+            let len = reader.read_u32::<BigEndian>()? as usize;
+            for _ in 0..len {
+                h.push(read_g1(&mut reader)?);
+            }
+        }
+
+        {
+            let len = reader.read_u32::<BigEndian>()? as usize;
+            for _ in 0..len {
+                l.push(read_g1(&mut reader)?);
+            }
+        }
+
+        {
+            let len = reader.read_u32::<BigEndian>()? as usize;
+            for _ in 0..len {
+                a.push(read_g1(&mut reader)?);
+            }
+        }
+
+        {
+            let len = reader.read_u32::<BigEndian>()? as usize;
+            for _ in 0..len {
+                b_g1.push(read_g1(&mut reader)?);
+            }
+        }
+
+        {
+            let len = reader.read_u32::<BigEndian>()? as usize;
+            for _ in 0..len {
+                b_g2.push(read_g2(&mut reader)?);
+            }
+        }
+
+        Ok(Parameters {
+            vk,
+            h: Arc::new(h),
+            l: Arc::new(l),
+            a: Arc::new(a),
+            b_g1: Arc::new(b_g1),
+            b_g2: Arc::new(b_g2),
+        })
+    }
+}
+
+pub struct PreparedVerifyingKey<E: Engine> {
+    /// Pairing result of alpha*beta
+    alpha_g1_beta_g2: E::Fqk,
+    /// -gamma in G2
+    neg_gamma_g2: <E::G2Affine as PairingCurveAffine>::Prepared,
+    /// -delta in G2
+    neg_delta_g2: <E::G2Affine as PairingCurveAffine>::Prepared,
+    /// Copy of IC from `VerifiyingKey`.
+    ic: Vec<E::G1Affine>,
+}
+
+pub trait ParameterSource<E: Engine> {
+    type G1Builder: SourceBuilder<E::G1Affine>;
+    type G2Builder: SourceBuilder<E::G2Affine>;
+
+    fn get_vk(&mut self, num_ic: usize) -> Result<VerifyingKey<E>, SynthesisError>;
+    fn get_h(&mut self, num_h: usize) -> Result<Self::G1Builder, SynthesisError>;
+    fn get_l(&mut self, num_l: usize) -> Result<Self::G1Builder, SynthesisError>;
+    fn get_a(
+        &mut self,
+        num_inputs: usize,
+        num_aux: usize,
+    ) -> Result<(Self::G1Builder, Self::G1Builder), SynthesisError>;
+    fn get_b_g1(
+        &mut self,
+        num_inputs: usize,
+        num_aux: usize,
+    ) -> Result<(Self::G1Builder, Self::G1Builder), SynthesisError>;
+    fn get_b_g2(
+        &mut self,
+        num_inputs: usize,
+        num_aux: usize,
+    ) -> Result<(Self::G2Builder, Self::G2Builder), SynthesisError>;
+}
+
+impl<'a, E: Engine> ParameterSource<E> for &'a Parameters<E> {
+    type G1Builder = (Arc<Vec<E::G1Affine>>, usize);
+    type G2Builder = (Arc<Vec<E::G2Affine>>, usize);
+
+    fn get_vk(&mut self, _: usize) -> Result<VerifyingKey<E>, SynthesisError> {
+        Ok(self.vk.clone())
+    }
+
+    fn get_h(&mut self, _: usize) -> Result<Self::G1Builder, SynthesisError> {
+        Ok((self.h.clone(), 0))
+    }
+
+    fn get_l(&mut self, _: usize) -> Result<Self::G1Builder, SynthesisError> {
+        Ok((self.l.clone(), 0))
+    }
+
+    fn get_a(
+        &mut self,
+        num_inputs: usize,
+        _: usize,
+    ) -> Result<(Self::G1Builder, Self::G1Builder), SynthesisError> {
+        Ok(((self.a.clone(), 0), (self.a.clone(), num_inputs)))
+    }
+
+    fn get_b_g1(
+        &mut self,
+        num_inputs: usize,
+        _: usize,
+    ) -> Result<(Self::G1Builder, Self::G1Builder), SynthesisError> {
+        Ok(((self.b_g1.clone(), 0), (self.b_g1.clone(), num_inputs)))
+    }
+
+    fn get_b_g2(
+        &mut self,
+        num_inputs: usize,
+        _: usize,
+    ) -> Result<(Self::G2Builder, Self::G2Builder), SynthesisError> {
+        Ok(((self.b_g2.clone(), 0), (self.b_g2.clone(), num_inputs)))
+    }
+}
+
+#[cfg(test)]
+mod test_with_bls12_381 {
+    use super::*;
+    use crate::{Circuit, ConstraintSystem, SynthesisError};
+
+    use ff::Field;
+    use pairing::bls12_381::{Bls12, Fr};
+    use rand::thread_rng;
+
+    #[test]
+    fn serialization() {
+        struct MySillyCircuit<E: Engine> {
+            a: Option<E::Fr>,
+            b: Option<E::Fr>,
+        }
+
+        impl<E: Engine> Circuit<E> for MySillyCircuit<E> {
+            fn synthesize<CS: ConstraintSystem<E>>(
+                self,
+                cs: &mut CS,
+            ) -> Result<(), SynthesisError> {
+                let a = cs.alloc(|| "a", || self.a.ok_or(SynthesisError::AssignmentMissing))?;
+                let b = cs.alloc(|| "b", || self.b.ok_or(SynthesisError::AssignmentMissing))?;
+                let c = cs.alloc_input(
+                    || "c",
+                    || {
+                        let mut a = self.a.ok_or(SynthesisError::AssignmentMissing)?;
+                        let b = self.b.ok_or(SynthesisError::AssignmentMissing)?;
+
+                        a.mul_assign(&b);
+                        Ok(a)
+                    },
+                )?;
+
+                cs.enforce(|| "a*b=c", |lc| lc + a, |lc| lc + b, |lc| lc + c);
+
+                Ok(())
+            }
+        }
+
+        let rng = &mut thread_rng();
+
+        let params =
+            generate_random_parameters::<Bls12, _, _>(MySillyCircuit { a: None, b: None }, rng)
+                .unwrap();
+
+        {
+            let mut v = vec![];
+
+            params.write(&mut v).unwrap();
+            assert_eq!(v.len(), 2136);
+
+            let de_params = Parameters::read(&v[..], true).unwrap();
+            assert!(params == de_params);
+
+            let de_params = Parameters::read(&v[..], false).unwrap();
+            assert!(params == de_params);
+        }
+
+        let pvk = prepare_verifying_key::<Bls12>(&params.vk);
+
+        for _ in 0..100 {
+            let a = Fr::random(rng);
+            let b = Fr::random(rng);
+            let mut c = a;
+            c.mul_assign(&b);
+
+            let proof = create_random_proof(
+                MySillyCircuit {
+                    a: Some(a),
+                    b: Some(b),
+                },
+                &params,
+                rng,
+            )
+            .unwrap();
+
+            let mut v = vec![];
+            proof.write(&mut v).unwrap();
+
+            assert_eq!(v.len(), 192);
+
+            let de_proof = Proof::read(&v[..]).unwrap();
+            assert!(proof == de_proof);
+
+            assert!(verify_proof(&pvk, &proof, &[c]).unwrap());
+            assert!(!verify_proof(&pvk, &proof, &[a]).unwrap());
+        }
+    }
+}

bellman/src/groth16/prover.rs

@@ -0,0 +1,351 @@
+use rand_core::RngCore;
+
+use std::sync::Arc;
+
+use futures::Future;
+
+use ff::{Field, PrimeField};
+use group::{CurveAffine, CurveProjective};
+use pairing::Engine;
+
+use super::{ParameterSource, Proof};
+
+use crate::{Circuit, ConstraintSystem, Index, LinearCombination, SynthesisError, Variable};
+
+use crate::domain::{EvaluationDomain, Scalar};
+
+use crate::multiexp::{multiexp, DensityTracker, FullDensity};
+
+use crate::multicore::Worker;
+
+fn eval<E: Engine>(
+    lc: &LinearCombination<E>,
+    mut input_density: Option<&mut DensityTracker>,
+    mut aux_density: Option<&mut DensityTracker>,
+    input_assignment: &[E::Fr],
+    aux_assignment: &[E::Fr],
+) -> E::Fr {
+    let mut acc = E::Fr::zero();
+
+    for &(index, coeff) in lc.0.iter() {
+        let mut tmp;
+
+        match index {
+            Variable(Index::Input(i)) => {
+                tmp = input_assignment[i];
+                if let Some(ref mut v) = input_density {
+                    v.inc(i);
+                }
+            }
+            Variable(Index::Aux(i)) => {
+                tmp = aux_assignment[i];
+                if let Some(ref mut v) = aux_density {
+                    v.inc(i);
+                }
+            }
+        }
+
+        if coeff == E::Fr::one() {
+            acc.add_assign(&tmp);
+        } else {
+            tmp.mul_assign(&coeff);
+            acc.add_assign(&tmp);
+        }
+    }
+
+    acc
+}
+
+struct ProvingAssignment<E: Engine> {
+    // Density of queries
+    a_aux_density: DensityTracker,
+    b_input_density: DensityTracker,
+    b_aux_density: DensityTracker,
+
+    // Evaluations of A, B, C polynomials
+    a: Vec<Scalar<E>>,
+    b: Vec<Scalar<E>>,
+    c: Vec<Scalar<E>>,
+
+    // Assignments of variables
+    input_assignment: Vec<E::Fr>,
+    aux_assignment: Vec<E::Fr>,
+}
+
+impl<E: Engine> ConstraintSystem<E> for ProvingAssignment<E> {
+    type Root = Self;
+
+    fn alloc<F, A, AR>(&mut self, _: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        self.aux_assignment.push(f()?);
+        self.a_aux_density.add_element();
+        self.b_aux_density.add_element();
+
+        Ok(Variable(Index::Aux(self.aux_assignment.len() - 1)))
+    }
+
+    fn alloc_input<F, A, AR>(&mut self, _: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        self.input_assignment.push(f()?);
+        self.b_input_density.add_element();
+
+        Ok(Variable(Index::Input(self.input_assignment.len() - 1)))
+    }
+
+    fn enforce<A, AR, LA, LB, LC>(&mut self, _: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+    {
+        let a = a(LinearCombination::zero());
+        let b = b(LinearCombination::zero());
+        let c = c(LinearCombination::zero());
+
+        self.a.push(Scalar(eval(
+            &a,
+            // Inputs have full density in the A query
+            // because there are constraints of the
+            // form x * 0 = 0 for each input.
+            None,
+            Some(&mut self.a_aux_density),
+            &self.input_assignment,
+            &self.aux_assignment,
+        )));
+        self.b.push(Scalar(eval(
+            &b,
+            Some(&mut self.b_input_density),
+            Some(&mut self.b_aux_density),
+            &self.input_assignment,
+            &self.aux_assignment,
+        )));
+        self.c.push(Scalar(eval(
+            &c,
+            // There is no C polynomial query,
+            // though there is an (beta)A + (alpha)B + C
+            // query for all aux variables.
+            // However, that query has full density.
+            None,
+            None,
+            &self.input_assignment,
+            &self.aux_assignment,
+        )));
+    }
+
+    fn push_namespace<NR, N>(&mut self, _: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        // Do nothing; we don't care about namespaces in this context.
+    }
+
+    fn pop_namespace(&mut self) {
+        // Do nothing; we don't care about namespaces in this context.
+    }
+
+    fn get_root(&mut self) -> &mut Self::Root {
+        self
+    }
+}
+
+pub fn create_random_proof<E, C, R, P: ParameterSource<E>>(
+    circuit: C,
+    params: P,
+    rng: &mut R,
+) -> Result<Proof<E>, SynthesisError>
+where
+    E: Engine,
+    C: Circuit<E>,
+    R: RngCore,
+{
+    let r = E::Fr::random(rng);
+    let s = E::Fr::random(rng);
+
+    create_proof::<E, C, P>(circuit, params, r, s)
+}
+
+pub fn create_proof<E, C, P: ParameterSource<E>>(
+    circuit: C,
+    mut params: P,
+    r: E::Fr,
+    s: E::Fr,
+) -> Result<Proof<E>, SynthesisError>
+where
+    E: Engine,
+    C: Circuit<E>,
+{
+    let mut prover = ProvingAssignment {
+        a_aux_density: DensityTracker::new(),
+        b_input_density: DensityTracker::new(),
+        b_aux_density: DensityTracker::new(),
+        a: vec![],
+        b: vec![],
+        c: vec![],
+        input_assignment: vec![],
+        aux_assignment: vec![],
+    };
+
+    prover.alloc_input(|| "", || Ok(E::Fr::one()))?;
+
+    circuit.synthesize(&mut prover)?;
+
+    for i in 0..prover.input_assignment.len() {
+        prover.enforce(|| "", |lc| lc + Variable(Index::Input(i)), |lc| lc, |lc| lc);
+    }
+
+    let worker = Worker::new();
+
+    let vk = params.get_vk(prover.input_assignment.len())?;
+
+    let h = {
+        let mut a = EvaluationDomain::from_coeffs(prover.a)?;
+        let mut b = EvaluationDomain::from_coeffs(prover.b)?;
+        let mut c = EvaluationDomain::from_coeffs(prover.c)?;
+        a.ifft(&worker);
+        a.coset_fft(&worker);
+        b.ifft(&worker);
+        b.coset_fft(&worker);
+        c.ifft(&worker);
+        c.coset_fft(&worker);
+
+        a.mul_assign(&worker, &b);
+        drop(b);
+        a.sub_assign(&worker, &c);
+        drop(c);
+        a.divide_by_z_on_coset(&worker);
+        a.icoset_fft(&worker);
+        let mut a = a.into_coeffs();
+        let a_len = a.len() - 1;
+        a.truncate(a_len);
+        // TODO: parallelize if it's even helpful
+        let a = Arc::new(a.into_iter().map(|s| s.0.into_repr()).collect::<Vec<_>>());
+
+        multiexp(&worker, params.get_h(a.len())?, FullDensity, a)
+    };
+
+    // TODO: parallelize if it's even helpful
+    let input_assignment = Arc::new(
+        prover
+            .input_assignment
+            .into_iter()
+            .map(|s| s.into_repr())
+            .collect::<Vec<_>>(),
+    );
+    let aux_assignment = Arc::new(
+        prover
+            .aux_assignment
+            .into_iter()
+            .map(|s| s.into_repr())
+            .collect::<Vec<_>>(),
+    );
+
+    let l = multiexp(
+        &worker,
+        params.get_l(aux_assignment.len())?,
+        FullDensity,
+        aux_assignment.clone(),
+    );
+
+    let a_aux_density_total = prover.a_aux_density.get_total_density();
+
+    let (a_inputs_source, a_aux_source) =
+        params.get_a(input_assignment.len(), a_aux_density_total)?;
+
+    let a_inputs = multiexp(
+        &worker,
+        a_inputs_source,
+        FullDensity,
+        input_assignment.clone(),
+    );
+    let a_aux = multiexp(
+        &worker,
+        a_aux_source,
+        Arc::new(prover.a_aux_density),
+        aux_assignment.clone(),
+    );
+
+    let b_input_density = Arc::new(prover.b_input_density);
+    let b_input_density_total = b_input_density.get_total_density();
+    let b_aux_density = Arc::new(prover.b_aux_density);
+    let b_aux_density_total = b_aux_density.get_total_density();
+
+    let (b_g1_inputs_source, b_g1_aux_source) =
+        params.get_b_g1(b_input_density_total, b_aux_density_total)?;
+
+    let b_g1_inputs = multiexp(
+        &worker,
+        b_g1_inputs_source,
+        b_input_density.clone(),
+        input_assignment.clone(),
+    );
+    let b_g1_aux = multiexp(
+        &worker,
+        b_g1_aux_source,
+        b_aux_density.clone(),
+        aux_assignment.clone(),
+    );
+
+    let (b_g2_inputs_source, b_g2_aux_source) =
+        params.get_b_g2(b_input_density_total, b_aux_density_total)?;
+
+    let b_g2_inputs = multiexp(
+        &worker,
+        b_g2_inputs_source,
+        b_input_density,
+        input_assignment,
+    );
+    let b_g2_aux = multiexp(&worker, b_g2_aux_source, b_aux_density, aux_assignment);
+
+    if vk.delta_g1.is_zero() || vk.delta_g2.is_zero() {
+        // If this element is zero, someone is trying to perform a
+        // subversion-CRS attack.
+        return Err(SynthesisError::UnexpectedIdentity);
+    }
+
+    let mut g_a = vk.delta_g1.mul(r);
+    g_a.add_assign_mixed(&vk.alpha_g1);
+    let mut g_b = vk.delta_g2.mul(s);
+    g_b.add_assign_mixed(&vk.beta_g2);
+    let mut g_c;
+    {
+        let mut rs = r;
+        rs.mul_assign(&s);
+
+        g_c = vk.delta_g1.mul(rs);
+        g_c.add_assign(&vk.alpha_g1.mul(s));
+        g_c.add_assign(&vk.beta_g1.mul(r));
+    }
+    let mut a_answer = a_inputs.wait()?;
+    a_answer.add_assign(&a_aux.wait()?);
+    g_a.add_assign(&a_answer);
+    a_answer.mul_assign(s);
+    g_c.add_assign(&a_answer);
+
+    let mut b1_answer = b_g1_inputs.wait()?;
+    b1_answer.add_assign(&b_g1_aux.wait()?);
+    let mut b2_answer = b_g2_inputs.wait()?;
+    b2_answer.add_assign(&b_g2_aux.wait()?);
+
+    g_b.add_assign(&b2_answer);
+    b1_answer.mul_assign(r);
+    g_c.add_assign(&b1_answer);
+    g_c.add_assign(&h.wait()?);
+    g_c.add_assign(&l.wait()?);
+
+    Ok(Proof {
+        a: g_a.into_affine(),
+        b: g_b.into_affine(),
+        c: g_c.into_affine(),
+    })
+}

bellman/src/groth16/tests/dummy_engine.rs

@@ -0,0 +1,448 @@
+use ff::{
+    Field, LegendreSymbol, PrimeField, PrimeFieldDecodingError, PrimeFieldRepr, ScalarEngine,
+    SqrtField,
+};
+use group::{CurveAffine, CurveProjective, EncodedPoint, GroupDecodingError};
+use pairing::{Engine, PairingCurveAffine};
+
+use rand_core::RngCore;
+use std::cmp::Ordering;
+use std::fmt;
+use std::num::Wrapping;
+
+const MODULUS_R: Wrapping<u32> = Wrapping(64513);
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Fr(Wrapping<u32>);
+
+impl fmt::Display for Fr {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        write!(f, "{}", (self.0).0)
+    }
+}
+
+impl Field for Fr {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+        Fr(Wrapping(rng.next_u32()) % MODULUS_R)
+    }
+
+    fn zero() -> Self {
+        Fr(Wrapping(0))
+    }
+
+    fn one() -> Self {
+        Fr(Wrapping(1))
+    }
+
+    fn is_zero(&self) -> bool {
+        (self.0).0 == 0
+    }
+
+    fn square(&mut self) {
+        self.0 = (self.0 * self.0) % MODULUS_R;
+    }
+
+    fn double(&mut self) {
+        self.0 = (self.0 << 1) % MODULUS_R;
+    }
+
+    fn negate(&mut self) {
+        if !<Fr as Field>::is_zero(self) {
+            self.0 = MODULUS_R - self.0;
+        }
+    }
+
+    fn add_assign(&mut self, other: &Self) {
+        self.0 = (self.0 + other.0) % MODULUS_R;
+    }
+
+    fn sub_assign(&mut self, other: &Self) {
+        self.0 = ((MODULUS_R + self.0) - other.0) % MODULUS_R;
+    }
+
+    fn mul_assign(&mut self, other: &Self) {
+        self.0 = (self.0 * other.0) % MODULUS_R;
+    }
+
+    fn inverse(&self) -> Option<Self> {
+        if <Fr as Field>::is_zero(self) {
+            None
+        } else {
+            Some(self.pow(&[(MODULUS_R.0 as u64) - 2]))
+        }
+    }
+
+    fn frobenius_map(&mut self, _: usize) {
+        // identity
+    }
+}
+
+impl SqrtField for Fr {
+    fn legendre(&self) -> LegendreSymbol {
+        // s = self^((r - 1) // 2)
+        let s = self.pow([32256]);
+        if s == <Fr as Field>::zero() {
+            LegendreSymbol::Zero
+        } else if s == <Fr as Field>::one() {
+            LegendreSymbol::QuadraticResidue
+        } else {
+            LegendreSymbol::QuadraticNonResidue
+        }
+    }
+
+    fn sqrt(&self) -> Option<Self> {
+        // Tonelli-Shank's algorithm for q mod 16 = 1
+        // https://eprint.iacr.org/2012/685.pdf (page 12, algorithm 5)
+        match self.legendre() {
+            LegendreSymbol::Zero => Some(*self),
+            LegendreSymbol::QuadraticNonResidue => None,
+            LegendreSymbol::QuadraticResidue => {
+                let mut c = Fr::root_of_unity();
+                // r = self^((t + 1) // 2)
+                let mut r = self.pow([32]);
+                // t = self^t
+                let mut t = self.pow([63]);
+                let mut m = Fr::S;
+
+                while t != <Fr as Field>::one() {
+                    let mut i = 1;
+                    {
+                        let mut t2i = t;
+                        t2i.square();
+                        loop {
+                            if t2i == <Fr as Field>::one() {
+                                break;
+                            }
+                            t2i.square();
+                            i += 1;
+                        }
+                    }
+
+                    for _ in 0..(m - i - 1) {
+                        c.square();
+                    }
+                    <Fr as Field>::mul_assign(&mut r, &c);
+                    c.square();
+                    <Fr as Field>::mul_assign(&mut t, &c);
+                    m = i;
+                }
+
+                Some(r)
+            }
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct FrRepr([u64; 1]);
+
+impl Ord for FrRepr {
+    fn cmp(&self, other: &FrRepr) -> Ordering {
+        (self.0)[0].cmp(&(other.0)[0])
+    }
+}
+
+impl PartialOrd for FrRepr {
+    fn partial_cmp(&self, other: &FrRepr) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl fmt::Display for FrRepr {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        write!(f, "{}", (self.0)[0])
+    }
+}
+
+impl From<u64> for FrRepr {
+    fn from(v: u64) -> FrRepr {
+        FrRepr([v])
+    }
+}
+
+impl From<Fr> for FrRepr {
+    fn from(v: Fr) -> FrRepr {
+        FrRepr([(v.0).0 as u64])
+    }
+}
+
+impl AsMut<[u64]> for FrRepr {
+    fn as_mut(&mut self) -> &mut [u64] {
+        &mut self.0[..]
+    }
+}
+
+impl AsRef<[u64]> for FrRepr {
+    fn as_ref(&self) -> &[u64] {
+        &self.0[..]
+    }
+}
+
+impl Default for FrRepr {
+    fn default() -> FrRepr {
+        FrRepr::from(0u64)
+    }
+}
+
+impl PrimeFieldRepr for FrRepr {
+    fn sub_noborrow(&mut self, other: &Self) {
+        self.0[0] = self.0[0].wrapping_sub(other.0[0]);
+    }
+    fn add_nocarry(&mut self, other: &Self) {
+        self.0[0] = self.0[0].wrapping_add(other.0[0]);
+    }
+    fn num_bits(&self) -> u32 {
+        64 - self.0[0].leading_zeros()
+    }
+    fn is_zero(&self) -> bool {
+        self.0[0] == 0
+    }
+    fn is_odd(&self) -> bool {
+        !self.is_even()
+    }
+    fn is_even(&self) -> bool {
+        self.0[0] % 2 == 0
+    }
+    fn div2(&mut self) {
+        self.shr(1)
+    }
+    fn shr(&mut self, amt: u32) {
+        self.0[0] >>= amt;
+    }
+    fn mul2(&mut self) {
+        self.shl(1)
+    }
+    fn shl(&mut self, amt: u32) {
+        self.0[0] <<= amt;
+    }
+}
+
+impl PrimeField for Fr {
+    type Repr = FrRepr;
+
+    const NUM_BITS: u32 = 16;
+    const CAPACITY: u32 = 15;
+    const S: u32 = 10;
+
+    fn from_repr(repr: FrRepr) -> Result<Self, PrimeFieldDecodingError> {
+        if repr.0[0] >= (MODULUS_R.0 as u64) {
+            Err(PrimeFieldDecodingError::NotInField(format!("{}", repr)))
+        } else {
+            Ok(Fr(Wrapping(repr.0[0] as u32)))
+        }
+    }
+
+    fn into_repr(&self) -> FrRepr {
+        FrRepr::from(*self)
+    }
+
+    fn char() -> FrRepr {
+        Fr(MODULUS_R).into()
+    }
+
+    fn multiplicative_generator() -> Fr {
+        Fr(Wrapping(5))
+    }
+
+    fn root_of_unity() -> Fr {
+        Fr(Wrapping(57751))
+    }
+}
+
+#[derive(Clone)]
+pub struct DummyEngine;
+
+impl ScalarEngine for DummyEngine {
+    type Fr = Fr;
+}
+
+impl Engine for DummyEngine {
+    type G1 = Fr;
+    type G1Affine = Fr;
+    type G2 = Fr;
+    type G2Affine = Fr;
+    type Fq = Fr;
+    type Fqe = Fr;
+
+    // TODO: This should be F_645131 or something. Doesn't matter for now.
+    type Fqk = Fr;
+
+    fn miller_loop<'a, I>(i: I) -> Self::Fqk
+    where
+        I: IntoIterator<
+            Item = &'a (
+                &'a <Self::G1Affine as PairingCurveAffine>::Prepared,
+                &'a <Self::G2Affine as PairingCurveAffine>::Prepared,
+            ),
+        >,
+    {
+        let mut acc = <Fr as Field>::zero();
+
+        for &(a, b) in i {
+            let mut tmp = *a;
+            <Fr as Field>::mul_assign(&mut tmp, b);
+            <Fr as Field>::add_assign(&mut acc, &tmp);
+        }
+
+        acc
+    }
+
+    /// Perform final exponentiation of the result of a miller loop.
+    fn final_exponentiation(this: &Self::Fqk) -> Option<Self::Fqk> {
+        Some(*this)
+    }
+}
+
+impl CurveProjective for Fr {
+    type Affine = Fr;
+    type Base = Fr;
+    type Scalar = Fr;
+    type Engine = DummyEngine;
+
+    fn random<R: RngCore>(rng: &mut R) -> Self {
+        <Fr as Field>::random(rng)
+    }
+
+    fn zero() -> Self {
+        <Fr as Field>::zero()
+    }
+
+    fn one() -> Self {
+        <Fr as Field>::one()
+    }
+
+    fn is_zero(&self) -> bool {
+        <Fr as Field>::is_zero(self)
+    }
+
+    fn batch_normalization(_: &mut [Self]) {}
+
+    fn is_normalized(&self) -> bool {
+        true
+    }
+
+    fn double(&mut self) {
+        <Fr as Field>::double(self);
+    }
+
+    fn add_assign(&mut self, other: &Self) {
+        <Fr as Field>::add_assign(self, other);
+    }
+
+    fn add_assign_mixed(&mut self, other: &Self) {
+        <Fr as Field>::add_assign(self, other);
+    }
+
+    fn negate(&mut self) {
+        <Fr as Field>::negate(self);
+    }
+
+    fn mul_assign<S: Into<<Self::Scalar as PrimeField>::Repr>>(&mut self, other: S) {
+        let tmp = Fr::from_repr(other.into()).unwrap();
+
+        <Fr as Field>::mul_assign(self, &tmp);
+    }
+
+    fn into_affine(&self) -> Fr {
+        *self
+    }
+
+    fn recommended_wnaf_for_scalar(_: <Self::Scalar as PrimeField>::Repr) -> usize {
+        3
+    }
+
+    fn recommended_wnaf_for_num_scalars(_: usize) -> usize {
+        3
+    }
+}
+
+#[derive(Copy, Clone)]
+pub struct FakePoint;
+
+impl AsMut<[u8]> for FakePoint {
+    fn as_mut(&mut self) -> &mut [u8] {
+        unimplemented!()
+    }
+}
+
+impl AsRef<[u8]> for FakePoint {
+    fn as_ref(&self) -> &[u8] {
+        unimplemented!()
+    }
+}
+
+impl EncodedPoint for FakePoint {
+    type Affine = Fr;
+
+    fn empty() -> Self {
+        unimplemented!()
+    }
+
+    fn size() -> usize {
+        unimplemented!()
+    }
+
+    fn into_affine(&self) -> Result<Self::Affine, GroupDecodingError> {
+        unimplemented!()
+    }
+
+    fn into_affine_unchecked(&self) -> Result<Self::Affine, GroupDecodingError> {
+        unimplemented!()
+    }
+
+    fn from_affine(_: Self::Affine) -> Self {
+        unimplemented!()
+    }
+}
+
+impl CurveAffine for Fr {
+    type Compressed = FakePoint;
+    type Uncompressed = FakePoint;
+    type Projective = Fr;
+    type Base = Fr;
+    type Scalar = Fr;
+    type Engine = DummyEngine;
+
+    fn zero() -> Self {
+        <Fr as Field>::zero()
+    }
+
+    fn one() -> Self {
+        <Fr as Field>::one()
+    }
+
+    fn is_zero(&self) -> bool {
+        <Fr as Field>::is_zero(self)
+    }
+
+    fn negate(&mut self) {
+        <Fr as Field>::negate(self);
+    }
+
+    fn mul<S: Into<<Self::Scalar as PrimeField>::Repr>>(&self, other: S) -> Self::Projective {
+        let mut res = *self;
+        let tmp = Fr::from_repr(other.into()).unwrap();
+
+        <Fr as Field>::mul_assign(&mut res, &tmp);
+
+        res
+    }
+
+    fn into_projective(&self) -> Self::Projective {
+        *self
+    }
+}
+
+impl PairingCurveAffine for Fr {
+    type Prepared = Fr;
+    type Pair = Fr;
+    type PairingResult = Fr;
+
+    fn prepare(&self) -> Self::Prepared {
+        *self
+    }
+
+    fn pairing_with(&self, other: &Self::Pair) -> Self::PairingResult {
+        self.mul(*other)
+    }
+}

bellman/src/groth16/tests/mod.rs

@@ -0,0 +1,381 @@
+use ff::{Field, PrimeField};
+use pairing::Engine;
+
+mod dummy_engine;
+use self::dummy_engine::*;
+
+use std::marker::PhantomData;
+
+use crate::{Circuit, ConstraintSystem, SynthesisError};
+
+use super::{create_proof, generate_parameters, prepare_verifying_key, verify_proof};
+
+struct XORDemo<E: Engine> {
+    a: Option<bool>,
+    b: Option<bool>,
+    _marker: PhantomData<E>,
+}
+
+impl<E: Engine> Circuit<E> for XORDemo<E> {
+    fn synthesize<CS: ConstraintSystem<E>>(self, cs: &mut CS) -> Result<(), SynthesisError> {
+        let a_var = cs.alloc(
+            || "a",
+            || {
+                if self.a.is_some() {
+                    if self.a.unwrap() {
+                        Ok(E::Fr::one())
+                    } else {
+                        Ok(E::Fr::zero())
+                    }
+                } else {
+                    Err(SynthesisError::AssignmentMissing)
+                }
+            },
+        )?;
+
+        cs.enforce(
+            || "a_boolean_constraint",
+            |lc| lc + CS::one() - a_var,
+            |lc| lc + a_var,
+            |lc| lc,
+        );
+
+        let b_var = cs.alloc(
+            || "b",
+            || {
+                if self.b.is_some() {
+                    if self.b.unwrap() {
+                        Ok(E::Fr::one())
+                    } else {
+                        Ok(E::Fr::zero())
+                    }
+                } else {
+                    Err(SynthesisError::AssignmentMissing)
+                }
+            },
+        )?;
+
+        cs.enforce(
+            || "b_boolean_constraint",
+            |lc| lc + CS::one() - b_var,
+            |lc| lc + b_var,
+            |lc| lc,
+        );
+
+        let c_var = cs.alloc_input(
+            || "c",
+            || {
+                if self.a.is_some() && self.b.is_some() {
+                    if self.a.unwrap() ^ self.b.unwrap() {
+                        Ok(E::Fr::one())
+                    } else {
+                        Ok(E::Fr::zero())
+                    }
+                } else {
+                    Err(SynthesisError::AssignmentMissing)
+                }
+            },
+        )?;
+
+        cs.enforce(
+            || "c_xor_constraint",
+            |lc| lc + a_var + a_var,
+            |lc| lc + b_var,
+            |lc| lc + a_var + b_var - c_var,
+        );
+
+        Ok(())
+    }
+}
+
+#[test]
+fn test_xordemo() {
+    let g1 = Fr::one();
+    let g2 = Fr::one();
+    let alpha = Fr::from_str("48577").unwrap();
+    let beta = Fr::from_str("22580").unwrap();
+    let gamma = Fr::from_str("53332").unwrap();
+    let delta = Fr::from_str("5481").unwrap();
+    let tau = Fr::from_str("3673").unwrap();
+
+    let params = {
+        let c = XORDemo::<DummyEngine> {
+            a: None,
+            b: None,
+            _marker: PhantomData,
+        };
+
+        generate_parameters(c, g1, g2, alpha, beta, gamma, delta, tau).unwrap()
+    };
+
+    // This will synthesize the constraint system:
+    //
+    // public inputs: a_0 = 1, a_1 = c
+    // aux inputs: a_2 = a, a_3 = b
+    // constraints:
+    //     (a_0 - a_2) * (a_2) = 0
+    //     (a_0 - a_3) * (a_3) = 0
+    //     (a_2 + a_2) * (a_3) = (a_2 + a_3 - a_1)
+    //     (a_0) * 0 = 0
+    //     (a_1) * 0 = 0
+
+    // The evaluation domain is 8. The H query should
+    // have 7 elements (it's a quotient polynomial)
+    assert_eq!(7, params.h.len());
+
+    let mut root_of_unity = Fr::root_of_unity();
+
+    // We expect this to be a 2^10 root of unity
+    assert_eq!(Fr::one(), root_of_unity.pow(&[1 << 10]));
+
+    // Let's turn it into a 2^3 root of unity.
+    root_of_unity = root_of_unity.pow(&[1 << 7]);
+    assert_eq!(Fr::one(), root_of_unity.pow(&[1 << 3]));
+    assert_eq!(Fr::from_str("20201").unwrap(), root_of_unity);
+
+    // Let's compute all the points in our evaluation domain.
+    let mut points = Vec::with_capacity(8);
+    for i in 0..8 {
+        points.push(root_of_unity.pow(&[i]));
+    }
+
+    // Let's compute t(tau) = (tau - p_0)(tau - p_1)...
+    //                      = tau^8 - 1
+    let mut t_at_tau = tau.pow(&[8]);
+    t_at_tau.sub_assign(&Fr::one());
+    {
+        let mut tmp = Fr::one();
+        for p in &points {
+            let mut term = tau;
+            term.sub_assign(p);
+            tmp.mul_assign(&term);
+        }
+        assert_eq!(tmp, t_at_tau);
+    }
+
+    // We expect our H query to be 7 elements of the form...
+    // {tau^i t(tau) / delta}
+    let delta_inverse = delta.inverse().unwrap();
+    let gamma_inverse = gamma.inverse().unwrap();
+    {
+        let mut coeff = delta_inverse;
+        coeff.mul_assign(&t_at_tau);
+
+        let mut cur = Fr::one();
+        for h in params.h.iter() {
+            let mut tmp = cur;
+            tmp.mul_assign(&coeff);
+
+            assert_eq!(*h, tmp);
+
+            cur.mul_assign(&tau);
+        }
+    }
+
+    // The density of the IC query is 2 (2 inputs)
+    assert_eq!(2, params.vk.ic.len());
+
+    // The density of the L query is 2 (2 aux variables)
+    assert_eq!(2, params.l.len());
+
+    // The density of the A query is 4 (each variable is in at least one A term)
+    assert_eq!(4, params.a.len());
+
+    // The density of the B query is 2 (two variables are in at least one B term)
+    assert_eq!(2, params.b_g1.len());
+    assert_eq!(2, params.b_g2.len());
+
+    /*
+    Lagrange interpolation polynomials in our evaluation domain:
+
+    ,-------------------------------. ,-------------------------------. ,-------------------------------.
+    |            A TERM             | |            B TERM             | |            C TERM             |
+    `-------------------------------. `-------------------------------' `-------------------------------'
+    | a_0   | a_1   | a_2   | a_3   | | a_0   | a_1   | a_2   | a_3   | | a_0   | a_1   | a_2   | a_3   |
+    | 1     | 0     | 64512 | 0     | | 0     | 0     | 1     | 0     | | 0     | 0     | 0     | 0     |
+    | 1     | 0     | 0     | 64512 | | 0     | 0     | 0     | 1     | | 0     | 0     | 0     | 0     |
+    | 0     | 0     | 2     | 0     | | 0     | 0     | 0     | 1     | | 0     | 64512 | 1     | 1     |
+    | 1     | 0     | 0     | 0     | | 0     | 0     | 0     | 0     | | 0     | 0     | 0     | 0     |
+    | 0     | 1     | 0     | 0     | | 0     | 0     | 0     | 0     | | 0     | 0     | 0     | 0     |
+    `-------'-------'-------'-------' `-------'-------'-------'-------' `-------'-------'-------'-------'
+
+    Example for u_0:
+
+    sage: r = 64513
+    sage: Fr = GF(r)
+    sage: omega = (Fr(5)^63)^(2^7)
+    sage: tau = Fr(3673)
+    sage: R.<x> = PolynomialRing(Fr, 'x')
+    sage: def eval(tau, c0, c1, c2, c3, c4):
+    ....:     p = R.lagrange_polynomial([(omega^0, c0), (omega^1, c1), (omega^2, c2), (omega^3, c3), (omega^4, c4), (omega^5, 0), (omega^6, 0), (omega^7, 0)])
+    ....:     return p.substitute(tau)
+    sage: eval(tau, 1, 1, 0, 1, 0)
+    59158
+    */
+
+    let u_i = [59158, 48317, 21767, 10402]
+        .iter()
+        .map(|e| Fr::from_str(&format!("{}", e)).unwrap())
+        .collect::<Vec<Fr>>();
+    let v_i = [0, 0, 60619, 30791]
+        .iter()
+        .map(|e| Fr::from_str(&format!("{}", e)).unwrap())
+        .collect::<Vec<Fr>>();
+    let w_i = [0, 23320, 41193, 41193]
+        .iter()
+        .map(|e| Fr::from_str(&format!("{}", e)).unwrap())
+        .collect::<Vec<Fr>>();
+
+    for (u, a) in u_i.iter().zip(&params.a[..]) {
+        assert_eq!(u, a);
+    }
+
+    for (v, b) in v_i
+        .iter()
+        .filter(|&&e| e != Fr::zero())
+        .zip(&params.b_g1[..])
+    {
+        assert_eq!(v, b);
+    }
+
+    for (v, b) in v_i
+        .iter()
+        .filter(|&&e| e != Fr::zero())
+        .zip(&params.b_g2[..])
+    {
+        assert_eq!(v, b);
+    }
+
+    for i in 0..4 {
+        let mut tmp1 = beta;
+        tmp1.mul_assign(&u_i[i]);
+
+        let mut tmp2 = alpha;
+        tmp2.mul_assign(&v_i[i]);
+
+        tmp1.add_assign(&tmp2);
+        tmp1.add_assign(&w_i[i]);
+
+        if i < 2 {
+            // Check the correctness of the IC query elements
+            tmp1.mul_assign(&gamma_inverse);
+
+            assert_eq!(tmp1, params.vk.ic[i]);
+        } else {
+            // Check the correctness of the L query elements
+            tmp1.mul_assign(&delta_inverse);
+
+            assert_eq!(tmp1, params.l[i - 2]);
+        }
+    }
+
+    // Check consistency of the other elements
+    assert_eq!(alpha, params.vk.alpha_g1);
+    assert_eq!(beta, params.vk.beta_g1);
+    assert_eq!(beta, params.vk.beta_g2);
+    assert_eq!(gamma, params.vk.gamma_g2);
+    assert_eq!(delta, params.vk.delta_g1);
+    assert_eq!(delta, params.vk.delta_g2);
+
+    let pvk = prepare_verifying_key(&params.vk);
+
+    let r = Fr::from_str("27134").unwrap();
+    let s = Fr::from_str("17146").unwrap();
+
+    let proof = {
+        let c = XORDemo {
+            a: Some(true),
+            b: Some(false),
+            _marker: PhantomData,
+        };
+
+        create_proof(c, &params, r, s).unwrap()
+    };
+
+    // A(x) =
+    //  a_0 * (44865*x^7 + 56449*x^6 + 44865*x^5 + 8064*x^4 + 3520*x^3 + 56449*x^2 + 3520*x + 40321) +
+    //  a_1 * (8064*x^7 + 56449*x^6 + 8064*x^5 + 56449*x^4 + 8064*x^3 + 56449*x^2 + 8064*x + 56449) +
+    //  a_2 * (16983*x^7 + 24192*x^6 + 63658*x^5 + 56449*x^4 + 16983*x^3 + 24192*x^2 + 63658*x + 56449) +
+    //  a_3 * (5539*x^7 + 27797*x^6 + 6045*x^5 + 56449*x^4 + 58974*x^3 + 36716*x^2 + 58468*x + 8064) +
+    {
+        // proof A = alpha + A(tau) + delta * r
+        let mut expected_a = delta;
+        expected_a.mul_assign(&r);
+        expected_a.add_assign(&alpha);
+        expected_a.add_assign(&u_i[0]); // a_0 = 1
+        expected_a.add_assign(&u_i[1]); // a_1 = 1
+        expected_a.add_assign(&u_i[2]); // a_2 = 1
+                                        // a_3 = 0
+        assert_eq!(proof.a, expected_a);
+    }
+
+    // B(x) =
+    // a_0 * (0) +
+    // a_1 * (0) +
+    // a_2 * (56449*x^7 + 56449*x^6 + 56449*x^5 + 56449*x^4 + 56449*x^3 + 56449*x^2 + 56449*x + 56449) +
+    // a_3 * (31177*x^7 + 44780*x^6 + 21752*x^5 + 42255*x^3 + 35861*x^2 + 33842*x + 48385)
+    {
+        // proof B = beta + B(tau) + delta * s
+        let mut expected_b = delta;
+        expected_b.mul_assign(&s);
+        expected_b.add_assign(&beta);
+        expected_b.add_assign(&v_i[0]); // a_0 = 1
+        expected_b.add_assign(&v_i[1]); // a_1 = 1
+        expected_b.add_assign(&v_i[2]); // a_2 = 1
+                                        // a_3 = 0
+        assert_eq!(proof.b, expected_b);
+    }
+
+    // C(x) =
+    // a_0 * (0) +
+    // a_1 * (27797*x^7 + 56449*x^6 + 36716*x^5 + 8064*x^4 + 27797*x^3 + 56449*x^2 + 36716*x + 8064) +
+    // a_2 * (36716*x^7 + 8064*x^6 + 27797*x^5 + 56449*x^4 + 36716*x^3 + 8064*x^2 + 27797*x + 56449) +
+    // a_3 * (36716*x^7 + 8064*x^6 + 27797*x^5 + 56449*x^4 + 36716*x^3 + 8064*x^2 + 27797*x + 56449)
+    //
+    // If A * B = C at each point in the domain, then the following polynomial...
+    // P(x) = A(x) * B(x) - C(x)
+    //      = 49752*x^14 + 13914*x^13 + 29243*x^12 + 27227*x^11 + 62362*x^10 + 35703*x^9 + 4032*x^8 + 14761*x^6 + 50599*x^5 + 35270*x^4 + 37286*x^3 + 2151*x^2 + 28810*x + 60481
+    //
+    // ... should be divisible by t(x), producing the quotient polynomial:
+    // h(x) = P(x) / t(x)
+    //      = 49752*x^6 + 13914*x^5 + 29243*x^4 + 27227*x^3 + 62362*x^2 + 35703*x + 4032
+    {
+        let mut expected_c = Fr::zero();
+
+        // A * s
+        let mut tmp = proof.a;
+        tmp.mul_assign(&s);
+        expected_c.add_assign(&tmp);
+
+        // B * r
+        let mut tmp = proof.b;
+        tmp.mul_assign(&r);
+        expected_c.add_assign(&tmp);
+
+        // delta * r * s
+        let mut tmp = delta;
+        tmp.mul_assign(&r);
+        tmp.mul_assign(&s);
+        expected_c.sub_assign(&tmp);
+
+        // L query answer
+        // a_2 = 1, a_3 = 0
+        expected_c.add_assign(&params.l[0]);
+
+        // H query answer
+        for (i, coeff) in [5040, 11763, 10755, 63633, 128, 9747, 8739]
+            .iter()
+            .enumerate()
+        {
+            let coeff = Fr::from_str(&format!("{}", coeff)).unwrap();
+
+            let mut tmp = params.h[i];
+            tmp.mul_assign(&coeff);
+            expected_c.add_assign(&tmp);
+        }
+
+        assert_eq!(expected_c, proof.c);
+    }
+
+    assert!(verify_proof(&pvk, &proof, &[Fr::one()]).unwrap());
+}

bellman/src/groth16/verifier.rs

@@ -0,0 +1,56 @@
+use ff::PrimeField;
+use group::{CurveAffine, CurveProjective};
+use pairing::{Engine, PairingCurveAffine};
+
+use super::{PreparedVerifyingKey, Proof, VerifyingKey};
+
+use crate::SynthesisError;
+
+pub fn prepare_verifying_key<E: Engine>(vk: &VerifyingKey<E>) -> PreparedVerifyingKey<E> {
+    let mut gamma = vk.gamma_g2;
+    gamma.negate();
+    let mut delta = vk.delta_g2;
+    delta.negate();
+
+    PreparedVerifyingKey {
+        alpha_g1_beta_g2: E::pairing(vk.alpha_g1, vk.beta_g2),
+        neg_gamma_g2: gamma.prepare(),
+        neg_delta_g2: delta.prepare(),
+        ic: vk.ic.clone(),
+    }
+}
+
+pub fn verify_proof<'a, E: Engine>(
+    pvk: &'a PreparedVerifyingKey<E>,
+    proof: &Proof<E>,
+    public_inputs: &[E::Fr],
+) -> Result<bool, SynthesisError> {
+    if (public_inputs.len() + 1) != pvk.ic.len() {
+        return Err(SynthesisError::MalformedVerifyingKey);
+    }
+
+    let mut acc = pvk.ic[0].into_projective();
+
+    for (i, b) in public_inputs.iter().zip(pvk.ic.iter().skip(1)) {
+        acc.add_assign(&b.mul(i.into_repr()));
+    }
+
+    // The original verification equation is:
+    // A * B = alpha * beta + inputs * gamma + C * delta
+    // ... however, we rearrange it so that it is:
+    // A * B - inputs * gamma - C * delta = alpha * beta
+    // or equivalently:
+    // A * B + inputs * (-gamma) + C * (-delta) = alpha * beta
+    // which allows us to do a single final exponentiation.
+
+    Ok(E::final_exponentiation(&E::miller_loop(
+        [
+            (&proof.a.prepare(), &proof.b.prepare()),
+            (&acc.into_affine().prepare(), &pvk.neg_gamma_g2),
+            (&proof.c.prepare(), &pvk.neg_delta_g2),
+        ]
+        .iter(),
+    ))
+    .unwrap()
+        == pvk.alpha_g1_beta_g2)
+}

bellman/src/lib.rs

@@ -0,0 +1,537 @@
+//! `bellman` is a crate for building zk-SNARK circuits. It provides circuit
+//! traits and and primitive structures, as well as basic gadget implementations
+//! such as booleans and number abstractions.
+//!
+//! # Example circuit
+//!
+//! Say we want to write a circuit that proves we know the preimage to some hash
+//! computed using SHA-256d (calling SHA-256 twice). The preimage must have a
+//! fixed length known in advance (because the circuit parameters will depend on
+//! it), but can otherwise have any value. We take the following strategy:
+//!
+//! - Witness each bit of the preimage.
+//! - Compute `hash = SHA-256d(preimage)` inside the circuit.
+//! - Expose `hash` as a public input using multiscalar packing.
+//!
+//! ```
+//! use bellman::{
+//!     gadgets::{
+//!         boolean::{AllocatedBit, Boolean},
+//!         multipack,
+//!         sha256::sha256,
+//!     },
+//!     groth16, Circuit, ConstraintSystem, SynthesisError,
+//! };
+//! use pairing::{bls12_381::Bls12, Engine};
+//! use rand::rngs::OsRng;
+//! use sha2::{Digest, Sha256};
+//!
+//! /// Our own SHA-256d gadget. Input and output are in little-endian bit order.
+//! fn sha256d<E: Engine, CS: ConstraintSystem<E>>(
+//!     mut cs: CS,
+//!     data: &[Boolean],
+//! ) -> Result<Vec<Boolean>, SynthesisError> {
+//!     // Flip endianness of each input byte
+//!     let input: Vec<_> = data
+//!         .chunks(8)
+//!         .map(|c| c.iter().rev())
+//!         .flatten()
+//!         .cloned()
+//!         .collect();
+//!
+//!     let mid = sha256(cs.namespace(|| "SHA-256(input)"), &input)?;
+//!     let res = sha256(cs.namespace(|| "SHA-256(mid)"), &mid)?;
+//!
+//!     // Flip endianness of each output byte
+//!     Ok(res
+//!         .chunks(8)
+//!         .map(|c| c.iter().rev())
+//!         .flatten()
+//!         .cloned()
+//!         .collect())
+//! }
+//!
+//! struct MyCircuit {
+//!     /// The input to SHA-256d we are proving that we know. Set to `None` when we
+//!     /// are verifying a proof (and do not have the witness data).
+//!     preimage: Option<[u8; 80]>,
+//! }
+//!
+//! impl<E: Engine> Circuit<E> for MyCircuit {
+//!     fn synthesize<CS: ConstraintSystem<E>>(self, cs: &mut CS) -> Result<(), SynthesisError> {
+//!         // Compute the values for the bits of the preimage. If we are verifying a proof,
+//!         // we still need to create the same constraints, so we return an equivalent-size
+//!         // Vec of None (indicating that the value of each bit is unknown).
+//!         let bit_values = if let Some(preimage) = self.preimage {
+//!             preimage
+//!                 .into_iter()
+//!                 .map(|byte| (0..8).map(move |i| (byte >> i) & 1u8 == 1u8))
+//!                 .flatten()
+//!                 .map(|b| Some(b))
+//!                 .collect()
+//!         } else {
+//!             vec![None; 80 * 8]
+//!         };
+//!         assert_eq!(bit_values.len(), 80 * 8);
+//!
+//!         // Witness the bits of the preimage.
+//!         let preimage_bits = bit_values
+//!             .into_iter()
+//!             .enumerate()
+//!             // Allocate each bit.
+//!             .map(|(i, b)| {
+//!                 AllocatedBit::alloc(cs.namespace(|| format!("preimage bit {}", i)), b)
+//!             })
+//!             // Convert the AllocatedBits into Booleans (required for the sha256 gadget).
+//!             .map(|b| b.map(Boolean::from))
+//!             .collect::<Result<Vec<_>, _>>()?;
+//!
+//!         // Compute hash = SHA-256d(preimage).
+//!         let hash = sha256d(cs.namespace(|| "SHA-256d(preimage)"), &preimage_bits)?;
+//!
+//!         // Expose the vector of 32 boolean variables as compact public inputs.
+//!         multipack::pack_into_inputs(cs.namespace(|| "pack hash"), &hash)
+//!     }
+//! }
+//!
+//! // Create parameters for our circuit. In a production deployment these would
+//! // be generated securely using a multiparty computation.
+//! let params = {
+//!     let c = MyCircuit { preimage: None };
+//!     groth16::generate_random_parameters::<Bls12, _, _>(c, &mut OsRng).unwrap()
+//! };
+//!
+//! // Prepare the verification key (for proof verification).
+//! let pvk = groth16::prepare_verifying_key(&params.vk);
+//!
+//! // Pick a preimage and compute its hash.
+//! let preimage = [42; 80];
+//! let hash = Sha256::digest(&Sha256::digest(&preimage));
+//!
+//! // Create an instance of our circuit (with the preimage as a witness).
+//! let c = MyCircuit {
+//!     preimage: Some(preimage),
+//! };
+//!
+//! // Create a Groth16 proof with our parameters.
+//! let proof = groth16::create_random_proof(c, &params, &mut OsRng).unwrap();
+//!
+//! // Pack the hash as inputs for proof verification.
+//! let hash_bits = multipack::bytes_to_bits_le(&hash);
+//! let inputs = multipack::compute_multipacking::<Bls12>(&hash_bits);
+//!
+//! // Check the proof!
+//! assert!(groth16::verify_proof(&pvk, &proof, &inputs).unwrap());
+//! ```
+//!
+//! # Roadmap
+//!
+//! `bellman` is being refactored into a generic proving library. Currently it
+//! is pairing-specific, and different types of proving systems need to be
+//! implemented as sub-modules. After the refactor, `bellman` will be generic
+//! using the [`ff`] and [`group`] crates, while specific proving systems will
+//! be separate crates that pull in the dependencies they require.
+
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
+pub mod domain;
+pub mod gadgets;
+#[cfg(feature = "groth16")]
+pub mod groth16;
+pub mod multicore;
+mod multiexp;
+
+use ff::{Field, ScalarEngine};
+
+use std::error::Error;
+use std::fmt;
+use std::io;
+use std::marker::PhantomData;
+use std::ops::{Add, Sub};
+
+/// Computations are expressed in terms of arithmetic circuits, in particular
+/// rank-1 quadratic constraint systems. The `Circuit` trait represents a
+/// circuit that can be synthesized. The `synthesize` method is called during
+/// CRS generation and during proving.
+pub trait Circuit<E: ScalarEngine> {
+    /// Synthesize the circuit into a rank-1 quadratic constraint system
+    fn synthesize<CS: ConstraintSystem<E>>(self, cs: &mut CS) -> Result<(), SynthesisError>;
+}
+
+/// Represents a variable in our constraint system.
+#[derive(Copy, Clone, Debug)]
+pub struct Variable(Index);
+
+impl Variable {
+    /// This constructs a variable with an arbitrary index.
+    /// Circuit implementations are not recommended to use this.
+    pub fn new_unchecked(idx: Index) -> Variable {
+        Variable(idx)
+    }
+
+    /// This returns the index underlying the variable.
+    /// Circuit implementations are not recommended to use this.
+    pub fn get_unchecked(&self) -> Index {
+        self.0
+    }
+}
+
+/// Represents the index of either an input variable or
+/// auxiliary variable.
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub enum Index {
+    Input(usize),
+    Aux(usize),
+}
+
+/// This represents a linear combination of some variables, with coefficients
+/// in the scalar field of a pairing-friendly elliptic curve group.
+#[derive(Clone)]
+pub struct LinearCombination<E: ScalarEngine>(Vec<(Variable, E::Fr)>);
+
+impl<E: ScalarEngine> AsRef<[(Variable, E::Fr)]> for LinearCombination<E> {
+    fn as_ref(&self) -> &[(Variable, E::Fr)] {
+        &self.0
+    }
+}
+
+impl<E: ScalarEngine> LinearCombination<E> {
+    pub fn zero() -> LinearCombination<E> {
+        LinearCombination(vec![])
+    }
+}
+
+impl<E: ScalarEngine> Add<(E::Fr, Variable)> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn add(mut self, (coeff, var): (E::Fr, Variable)) -> LinearCombination<E> {
+        self.0.push((var, coeff));
+
+        self
+    }
+}
+
+impl<E: ScalarEngine> Sub<(E::Fr, Variable)> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    #[allow(clippy::suspicious_arithmetic_impl)]
+    fn sub(self, (mut coeff, var): (E::Fr, Variable)) -> LinearCombination<E> {
+        coeff.negate();
+
+        self + (coeff, var)
+    }
+}
+
+impl<E: ScalarEngine> Add<Variable> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn add(self, other: Variable) -> LinearCombination<E> {
+        self + (E::Fr::one(), other)
+    }
+}
+
+impl<E: ScalarEngine> Sub<Variable> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn sub(self, other: Variable) -> LinearCombination<E> {
+        self - (E::Fr::one(), other)
+    }
+}
+
+impl<'a, E: ScalarEngine> Add<&'a LinearCombination<E>> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn add(mut self, other: &'a LinearCombination<E>) -> LinearCombination<E> {
+        for s in &other.0 {
+            self = self + (s.1, s.0);
+        }
+
+        self
+    }
+}
+
+impl<'a, E: ScalarEngine> Sub<&'a LinearCombination<E>> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn sub(mut self, other: &'a LinearCombination<E>) -> LinearCombination<E> {
+        for s in &other.0 {
+            self = self - (s.1, s.0);
+        }
+
+        self
+    }
+}
+
+impl<'a, E: ScalarEngine> Add<(E::Fr, &'a LinearCombination<E>)> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn add(mut self, (coeff, other): (E::Fr, &'a LinearCombination<E>)) -> LinearCombination<E> {
+        for s in &other.0 {
+            let mut tmp = s.1;
+            tmp.mul_assign(&coeff);
+            self = self + (tmp, s.0);
+        }
+
+        self
+    }
+}
+
+impl<'a, E: ScalarEngine> Sub<(E::Fr, &'a LinearCombination<E>)> for LinearCombination<E> {
+    type Output = LinearCombination<E>;
+
+    fn sub(mut self, (coeff, other): (E::Fr, &'a LinearCombination<E>)) -> LinearCombination<E> {
+        for s in &other.0 {
+            let mut tmp = s.1;
+            tmp.mul_assign(&coeff);
+            self = self - (tmp, s.0);
+        }
+
+        self
+    }
+}
+
+/// This is an error that could occur during circuit synthesis contexts,
+/// such as CRS generation, proving or verification.
+#[derive(Debug)]
+pub enum SynthesisError {
+    /// During synthesis, we lacked knowledge of a variable assignment.
+    AssignmentMissing,
+    /// During synthesis, we divided by zero.
+    DivisionByZero,
+    /// During synthesis, we constructed an unsatisfiable constraint system.
+    Unsatisfiable,
+    /// During synthesis, our polynomials ended up being too high of degree
+    PolynomialDegreeTooLarge,
+    /// During proof generation, we encountered an identity in the CRS
+    UnexpectedIdentity,
+    /// During proof generation, we encountered an I/O error with the CRS
+    IoError(io::Error),
+    /// During verification, our verifying key was malformed.
+    MalformedVerifyingKey,
+    /// During CRS generation, we observed an unconstrained auxiliary variable
+    UnconstrainedVariable,
+}
+
+impl From<io::Error> for SynthesisError {
+    fn from(e: io::Error) -> SynthesisError {
+        SynthesisError::IoError(e)
+    }
+}
+
+impl Error for SynthesisError {
+    fn description(&self) -> &str {
+        match *self {
+            SynthesisError::AssignmentMissing => {
+                "an assignment for a variable could not be computed"
+            }
+            SynthesisError::DivisionByZero => "division by zero",
+            SynthesisError::Unsatisfiable => "unsatisfiable constraint system",
+            SynthesisError::PolynomialDegreeTooLarge => "polynomial degree is too large",
+            SynthesisError::UnexpectedIdentity => "encountered an identity element in the CRS",
+            SynthesisError::IoError(_) => "encountered an I/O error",
+            SynthesisError::MalformedVerifyingKey => "malformed verifying key",
+            SynthesisError::UnconstrainedVariable => "auxiliary variable was unconstrained",
+        }
+    }
+}
+
+impl fmt::Display for SynthesisError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        if let SynthesisError::IoError(ref e) = *self {
+            write!(f, "I/O error: ")?;
+            e.fmt(f)
+        } else {
+            write!(f, "{}", self.description())
+        }
+    }
+}
+
+/// Represents a constraint system which can have new variables
+/// allocated and constrains between them formed.
+pub trait ConstraintSystem<E: ScalarEngine>: Sized {
+    /// Represents the type of the "root" of this constraint system
+    /// so that nested namespaces can minimize indirection.
+    type Root: ConstraintSystem<E>;
+
+    /// Return the "one" input variable
+    fn one() -> Variable {
+        Variable::new_unchecked(Index::Input(0))
+    }
+
+    /// Allocate a private variable in the constraint system. The provided function is used to
+    /// determine the assignment of the variable. The given `annotation` function is invoked
+    /// in testing contexts in order to derive a unique name for this variable in the current
+    /// namespace.
+    fn alloc<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>;
+
+    /// Allocate a public variable in the constraint system. The provided function is used to
+    /// determine the assignment of the variable.
+    fn alloc_input<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>;
+
+    /// Enforce that `A` * `B` = `C`. The `annotation` function is invoked in testing contexts
+    /// in order to derive a unique name for the constraint in the current namespace.
+    fn enforce<A, AR, LA, LB, LC>(&mut self, annotation: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>;
+
+    /// Create a new (sub)namespace and enter into it. Not intended
+    /// for downstream use; use `namespace` instead.
+    fn push_namespace<NR, N>(&mut self, name_fn: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR;
+
+    /// Exit out of the existing namespace. Not intended for
+    /// downstream use; use `namespace` instead.
+    fn pop_namespace(&mut self);
+
+    /// Gets the "root" constraint system, bypassing the namespacing.
+    /// Not intended for downstream use; use `namespace` instead.
+    fn get_root(&mut self) -> &mut Self::Root;
+
+    /// Begin a namespace for this constraint system.
+    fn namespace<NR, N>(&mut self, name_fn: N) -> Namespace<'_, E, Self::Root>
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        self.get_root().push_namespace(name_fn);
+
+        Namespace(self.get_root(), PhantomData)
+    }
+}
+
+/// This is a "namespaced" constraint system which borrows a constraint system (pushing
+/// a namespace context) and, when dropped, pops out of the namespace context.
+pub struct Namespace<'a, E: ScalarEngine, CS: ConstraintSystem<E>>(&'a mut CS, PhantomData<E>);
+
+impl<'cs, E: ScalarEngine, CS: ConstraintSystem<E>> ConstraintSystem<E> for Namespace<'cs, E, CS> {
+    type Root = CS::Root;
+
+    fn one() -> Variable {
+        CS::one()
+    }
+
+    fn alloc<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        self.0.alloc(annotation, f)
+    }
+
+    fn alloc_input<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        self.0.alloc_input(annotation, f)
+    }
+
+    fn enforce<A, AR, LA, LB, LC>(&mut self, annotation: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+    {
+        self.0.enforce(annotation, a, b, c)
+    }
+
+    // Downstream users who use `namespace` will never interact with these
+    // functions and they will never be invoked because the namespace is
+    // never a root constraint system.
+
+    fn push_namespace<NR, N>(&mut self, _: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        panic!("only the root's push_namespace should be called");
+    }
+
+    fn pop_namespace(&mut self) {
+        panic!("only the root's pop_namespace should be called");
+    }
+
+    fn get_root(&mut self) -> &mut Self::Root {
+        self.0.get_root()
+    }
+}
+
+impl<'a, E: ScalarEngine, CS: ConstraintSystem<E>> Drop for Namespace<'a, E, CS> {
+    fn drop(&mut self) {
+        self.get_root().pop_namespace()
+    }
+}
+
+/// Convenience implementation of ConstraintSystem<E> for mutable references to
+/// constraint systems.
+impl<'cs, E: ScalarEngine, CS: ConstraintSystem<E>> ConstraintSystem<E> for &'cs mut CS {
+    type Root = CS::Root;
+
+    fn one() -> Variable {
+        CS::one()
+    }
+
+    fn alloc<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        (**self).alloc(annotation, f)
+    }
+
+    fn alloc_input<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
+    where
+        F: FnOnce() -> Result<E::Fr, SynthesisError>,
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+    {
+        (**self).alloc_input(annotation, f)
+    }
+
+    fn enforce<A, AR, LA, LB, LC>(&mut self, annotation: A, a: LA, b: LB, c: LC)
+    where
+        A: FnOnce() -> AR,
+        AR: Into<String>,
+        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
+    {
+        (**self).enforce(annotation, a, b, c)
+    }
+
+    fn push_namespace<NR, N>(&mut self, name_fn: N)
+    where
+        NR: Into<String>,
+        N: FnOnce() -> NR,
+    {
+        (**self).push_namespace(name_fn)
+    }
+
+    fn pop_namespace(&mut self) {
+        (**self).pop_namespace()
+    }
+
+    fn get_root(&mut self) -> &mut Self::Root {
+        (**self).get_root()
+    }
+}

bellman/src/multicore.rs

@@ -0,0 +1,164 @@
+//! An interface for dealing with the kinds of parallel computations involved in
+//! `bellman`. It's currently just a thin wrapper around [`CpuPool`] and
+//! [`crossbeam`] but may be extended in the future to allow for various
+//! parallelism strategies.
+//!
+//! [`CpuPool`]: futures_cpupool::CpuPool
+
+#[cfg(feature = "multicore")]
+mod implementation {
+    use crossbeam::{self, thread::Scope};
+    use futures::{Future, IntoFuture, Poll};
+    use futures_cpupool::{CpuFuture, CpuPool};
+    use num_cpus;
+
+    #[derive(Clone)]
+    pub struct Worker {
+        cpus: usize,
+        pool: CpuPool,
+    }
+
+    impl Worker {
+        // We don't expose this outside the library so that
+        // all `Worker` instances have the same number of
+        // CPUs configured.
+        pub(crate) fn new_with_cpus(cpus: usize) -> Worker {
+            Worker {
+                cpus,
+                pool: CpuPool::new(cpus),
+            }
+        }
+
+        pub fn new() -> Worker {
+            Self::new_with_cpus(num_cpus::get())
+        }
+
+        pub fn log_num_cpus(&self) -> u32 {
+            log2_floor(self.cpus)
+        }
+
+        pub fn compute<F, R>(&self, f: F) -> WorkerFuture<R::Item, R::Error>
+        where
+            F: FnOnce() -> R + Send + 'static,
+            R: IntoFuture + 'static,
+            R::Future: Send + 'static,
+            R::Item: Send + 'static,
+            R::Error: Send + 'static,
+        {
+            WorkerFuture {
+                future: self.pool.spawn_fn(f),
+            }
+        }
+
+        pub fn scope<'a, F, R>(&self, elements: usize, f: F) -> R
+        where
+            F: FnOnce(&Scope<'a>, usize) -> R,
+        {
+            let chunk_size = if elements < self.cpus {
+                1
+            } else {
+                elements / self.cpus
+            };
+
+            // TODO: Handle case where threads fail
+            crossbeam::scope(|scope| f(scope, chunk_size))
+                .expect("Threads aren't allowed to fail yet")
+        }
+    }
+
+    pub struct WorkerFuture<T, E> {
+        future: CpuFuture<T, E>,
+    }
+
+    impl<T: Send + 'static, E: Send + 'static> Future for WorkerFuture<T, E> {
+        type Item = T;
+        type Error = E;
+
+        fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+            self.future.poll()
+        }
+    }
+
+    fn log2_floor(num: usize) -> u32 {
+        assert!(num > 0);
+
+        let mut pow = 0;
+
+        while (1 << (pow + 1)) <= num {
+            pow += 1;
+        }
+
+        pow
+    }
+
+    #[test]
+    fn test_log2_floor() {
+        assert_eq!(log2_floor(1), 0);
+        assert_eq!(log2_floor(2), 1);
+        assert_eq!(log2_floor(3), 1);
+        assert_eq!(log2_floor(4), 2);
+        assert_eq!(log2_floor(5), 2);
+        assert_eq!(log2_floor(6), 2);
+        assert_eq!(log2_floor(7), 2);
+        assert_eq!(log2_floor(8), 3);
+    }
+}
+
+#[cfg(not(feature = "multicore"))]
+mod implementation {
+    use futures::{future, Future, IntoFuture, Poll};
+
+    #[derive(Clone)]
+    pub struct Worker;
+
+    impl Worker {
+        pub fn new() -> Worker {
+            Worker
+        }
+
+        pub fn log_num_cpus(&self) -> u32 {
+            0
+        }
+
+        pub fn compute<F, R>(&self, f: F) -> R::Future
+        where
+            F: FnOnce() -> R + Send + 'static,
+            R: IntoFuture + 'static,
+            R::Future: Send + 'static,
+            R::Item: Send + 'static,
+            R::Error: Send + 'static,
+        {
+            f().into_future()
+        }
+
+        pub fn scope<F, R>(&self, elements: usize, f: F) -> R
+        where
+            F: FnOnce(&DummyScope, usize) -> R,
+        {
+            f(&DummyScope, elements)
+        }
+    }
+
+    pub struct WorkerFuture<T, E> {
+        future: future::FutureResult<T, E>,
+    }
+
+    impl<T: Send + 'static, E: Send + 'static> Future for WorkerFuture<T, E> {
+        type Item = T;
+        type Error = E;
+
+        fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+            self.future.poll()
+        }
+    }
+
+    pub struct DummyScope;
+
+    impl DummyScope {
+        pub fn spawn<F: FnOnce(&DummyScope)>(&self, f: F) {
+            f(self);
+        }
+    }
+}
+
+pub use self::implementation::*;

bellman/src/multiexp.rs

@@ -0,0 +1,324 @@
+use super::multicore::Worker;
+use bit_vec::{self, BitVec};
+use ff::{Field, PrimeField, PrimeFieldRepr, ScalarEngine};
+use futures::Future;
+use group::{CurveAffine, CurveProjective};
+use std::io;
+use std::iter;
+use std::sync::Arc;
+
+use super::SynthesisError;
+
+/// An object that builds a source of bases.
+pub trait SourceBuilder<G: CurveAffine>: Send + Sync + 'static + Clone {
+    type Source: Source<G>;
+
+    fn new(self) -> Self::Source;
+}
+
+/// A source of bases, like an iterator.
+pub trait Source<G: CurveAffine> {
+    /// Parses the element from the source. Fails if the point is at infinity.
+    fn add_assign_mixed(
+        &mut self,
+        to: &mut <G as CurveAffine>::Projective,
+    ) -> Result<(), SynthesisError>;
+
+    /// Skips `amt` elements from the source, avoiding deserialization.
+    fn skip(&mut self, amt: usize) -> Result<(), SynthesisError>;
+}
+
+impl<G: CurveAffine> SourceBuilder<G> for (Arc<Vec<G>>, usize) {
+    type Source = (Arc<Vec<G>>, usize);
+
+    fn new(self) -> (Arc<Vec<G>>, usize) {
+        (self.0.clone(), self.1)
+    }
+}
+
+impl<G: CurveAffine> Source<G> for (Arc<Vec<G>>, usize) {
+    fn add_assign_mixed(
+        &mut self,
+        to: &mut <G as CurveAffine>::Projective,
+    ) -> Result<(), SynthesisError> {
+        if self.0.len() <= self.1 {
+            return Err(io::Error::new(
+                io::ErrorKind::UnexpectedEof,
+                "expected more bases from source",
+            )
+            .into());
+        }
+
+        if self.0[self.1].is_zero() {
+            return Err(SynthesisError::UnexpectedIdentity);
+        }
+
+        to.add_assign_mixed(&self.0[self.1]);
+
+        self.1 += 1;
+
+        Ok(())
+    }
+
+    fn skip(&mut self, amt: usize) -> Result<(), SynthesisError> {
+        if self.0.len() <= self.1 {
+            return Err(io::Error::new(
+                io::ErrorKind::UnexpectedEof,
+                "expected more bases from source",
+            )
+            .into());
+        }
+
+        self.1 += amt;
+
+        Ok(())
+    }
+}
+
+pub trait QueryDensity {
+    /// Returns whether the base exists.
+    type Iter: Iterator<Item = bool>;
+
+    fn iter(self) -> Self::Iter;
+    fn get_query_size(self) -> Option<usize>;
+}
+
+#[derive(Clone)]
+pub struct FullDensity;
+
+impl AsRef<FullDensity> for FullDensity {
+    fn as_ref(&self) -> &FullDensity {
+        self
+    }
+}
+
+impl<'a> QueryDensity for &'a FullDensity {
+    type Iter = iter::Repeat<bool>;
+
+    fn iter(self) -> Self::Iter {
+        iter::repeat(true)
+    }
+
+    fn get_query_size(self) -> Option<usize> {
+        None
+    }
+}
+
+pub struct DensityTracker {
+    bv: BitVec,
+    total_density: usize,
+}
+
+impl<'a> QueryDensity for &'a DensityTracker {
+    type Iter = bit_vec::Iter<'a>;
+
+    fn iter(self) -> Self::Iter {
+        self.bv.iter()
+    }
+
+    fn get_query_size(self) -> Option<usize> {
+        Some(self.bv.len())
+    }
+}
+
+impl DensityTracker {
+    pub fn new() -> DensityTracker {
+        DensityTracker {
+            bv: BitVec::new(),
+            total_density: 0,
+        }
+    }
+
+    pub fn add_element(&mut self) {
+        self.bv.push(false);
+    }
+
+    pub fn inc(&mut self, idx: usize) {
+        if !self.bv.get(idx).unwrap() {
+            self.bv.set(idx, true);
+            self.total_density += 1;
+        }
+    }
+
+    pub fn get_total_density(&self) -> usize {
+        self.total_density
+    }
+}
+
+fn multiexp_inner<Q, D, G, S>(
+    pool: &Worker,
+    bases: S,
+    density_map: D,
+    exponents: Arc<Vec<<<G::Engine as ScalarEngine>::Fr as PrimeField>::Repr>>,
+    mut skip: u32,
+    c: u32,
+    handle_trivial: bool,
+) -> Box<dyn Future<Item = <G as CurveAffine>::Projective, Error = SynthesisError>>
+where
+    for<'a> &'a Q: QueryDensity,
+    D: Send + Sync + 'static + Clone + AsRef<Q>,
+    G: CurveAffine,
+    S: SourceBuilder<G>,
+{
+    // Perform this region of the multiexp
+    let this = {
+        let bases = bases.clone();
+        let exponents = exponents.clone();
+        let density_map = density_map.clone();
+
+        pool.compute(move || {
+            // Accumulate the result
+            let mut acc = G::Projective::zero();
+
+            // Build a source for the bases
+            let mut bases = bases.new();
+
+            // Create space for the buckets
+            let mut buckets = vec![<G as CurveAffine>::Projective::zero(); (1 << c) - 1];
+
+            let zero = <G::Engine as ScalarEngine>::Fr::zero().into_repr();
+            let one = <G::Engine as ScalarEngine>::Fr::one().into_repr();
+
+            // Sort the bases into buckets
+            for (&exp, density) in exponents.iter().zip(density_map.as_ref().iter()) {
+                if density {
+                    if exp == zero {
+                        bases.skip(1)?;
+                    } else if exp == one {
+                        if handle_trivial {
+                            bases.add_assign_mixed(&mut acc)?;
+                        } else {
+                            bases.skip(1)?;
+                        }
+                    } else {
+                        let mut exp = exp;
+                        exp.shr(skip);
+                        let exp = exp.as_ref()[0] % (1 << c);
+
+                        if exp != 0 {
+                            bases.add_assign_mixed(&mut buckets[(exp - 1) as usize])?;
+                        } else {
+                            bases.skip(1)?;
+                        }
+                    }
+                }
+            }
+
+            // Summation by parts
+            // e.g. 3a + 2b + 1c = a +
+            //                    (a) + b +
+            //                    ((a) + b) + c
+            let mut running_sum = G::Projective::zero();
+            for exp in buckets.into_iter().rev() {
+                running_sum.add_assign(&exp);
+                acc.add_assign(&running_sum);
+            }
+
+            Ok(acc)
+        })
+    };
+
+    skip += c;
+
+    if skip >= <G::Engine as ScalarEngine>::Fr::NUM_BITS {
+        // There isn't another region.
+        Box::new(this)
+    } else {
+        // There's another region more significant. Calculate and join it with
+        // this region recursively.
+        Box::new(
+            this.join(multiexp_inner(
+                pool,
+                bases,
+                density_map,
+                exponents,
+                skip,
+                c,
+                false,
+            ))
+            .map(move |(this, mut higher)| {
+                for _ in 0..c {
+                    higher.double();
+                }
+
+                higher.add_assign(&this);
+
+                higher
+            }),
+        )
+    }
+}
+
+/// Perform multi-exponentiation. The caller is responsible for ensuring the
+/// query size is the same as the number of exponents.
+pub fn multiexp<Q, D, G, S>(
+    pool: &Worker,
+    bases: S,
+    density_map: D,
+    exponents: Arc<Vec<<<G::Engine as ScalarEngine>::Fr as PrimeField>::Repr>>,
+) -> Box<dyn Future<Item = <G as CurveAffine>::Projective, Error = SynthesisError>>
+where
+    for<'a> &'a Q: QueryDensity,
+    D: Send + Sync + 'static + Clone + AsRef<Q>,
+    G: CurveAffine,
+    S: SourceBuilder<G>,
+{
+    let c = if exponents.len() < 32 {
+        3u32
+    } else {
+        (f64::from(exponents.len() as u32)).ln().ceil() as u32
+    };
+
+    if let Some(query_size) = density_map.as_ref().get_query_size() {
+        // If the density map has a known query size, it should not be
+        // inconsistent with the number of exponents.
+
+        assert!(query_size == exponents.len());
+    }
+
+    multiexp_inner(pool, bases, density_map, exponents, 0, c, true)
+}
+
+#[cfg(feature = "pairing")]
+#[test]
+fn test_with_bls12() {
+    fn naive_multiexp<G: CurveAffine>(
+        bases: Arc<Vec<G>>,
+        exponents: Arc<Vec<<G::Scalar as PrimeField>::Repr>>,
+    ) -> G::Projective {
+        assert_eq!(bases.len(), exponents.len());
+
+        let mut acc = G::Projective::zero();
+
+        for (base, exp) in bases.iter().zip(exponents.iter()) {
+            acc.add_assign(&base.mul(*exp));
+        }
+
+        acc
+    }
+
+    use pairing::{bls12_381::Bls12, Engine};
+    use rand;
+
+    const SAMPLES: usize = 1 << 14;
+
+    let rng = &mut rand::thread_rng();
+    let v = Arc::new(
+        (0..SAMPLES)
+            .map(|_| <Bls12 as ScalarEngine>::Fr::random(rng).into_repr())
+            .collect::<Vec<_>>(),
+    );
+    let g = Arc::new(
+        (0..SAMPLES)
+            .map(|_| <Bls12 as Engine>::G1::random(rng).into_affine())
+            .collect::<Vec<_>>(),
+    );
+
+    let naive = naive_multiexp(g.clone(), v.clone());
+
+    let pool = Worker::new();
+
+    let fast = multiexp(&pool, (g, 0), FullDensity, v).wait().unwrap();
+
+    assert_eq!(naive, fast);
+}

bellman/tests/mimc.rs

@@ -0,0 +1,229 @@
+// For randomness (during paramgen and proof generation)
+use rand::thread_rng;
+
+// For benchmarking
+use std::time::{Duration, Instant};
+
+// Bring in some tools for using pairing-friendly curves
+use ff::{Field, ScalarEngine};
+use pairing::Engine;
+
+// We're going to use the BLS12-381 pairing-friendly elliptic curve.
+use pairing::bls12_381::Bls12;
+
+// We'll use these interfaces to construct our circuit.
+use bellman::{Circuit, ConstraintSystem, SynthesisError};
+
+// We're going to use the Groth16 proving system.
+use bellman::groth16::{
+    create_random_proof, generate_random_parameters, prepare_verifying_key, verify_proof, Proof,
+};
+
+const MIMC_ROUNDS: usize = 322;
+
+/// This is an implementation of MiMC, specifically a
+/// variant named `LongsightF322p3` for BLS12-381.
+/// See http://eprint.iacr.org/2016/492 for more
+/// information about this construction.
+///
+/// ```
+/// function LongsightF322p3(xL ⦂ Fp, xR ⦂ Fp) {
+///     for i from 0 up to 321 {
+///         xL, xR := xR + (xL + Ci)^3, xL
+///     }
+///     return xL
+/// }
+/// ```
+fn mimc<E: Engine>(mut xl: E::Fr, mut xr: E::Fr, constants: &[E::Fr]) -> E::Fr {
+    assert_eq!(constants.len(), MIMC_ROUNDS);
+
+    for i in 0..MIMC_ROUNDS {
+        let mut tmp1 = xl;
+        tmp1.add_assign(&constants[i]);
+        let mut tmp2 = tmp1;
+        tmp2.square();
+        tmp2.mul_assign(&tmp1);
+        tmp2.add_assign(&xr);
+        xr = xl;
+        xl = tmp2;
+    }
+
+    xl
+}
+
+/// This is our demo circuit for proving knowledge of the
+/// preimage of a MiMC hash invocation.
+struct MiMCDemo<'a, E: Engine> {
+    xl: Option<E::Fr>,
+    xr: Option<E::Fr>,
+    constants: &'a [E::Fr],
+}
+
+/// Our demo circuit implements this `Circuit` trait which
+/// is used during paramgen and proving in order to
+/// synthesize the constraint system.
+impl<'a, E: Engine> Circuit<E> for MiMCDemo<'a, E> {
+    fn synthesize<CS: ConstraintSystem<E>>(self, cs: &mut CS) -> Result<(), SynthesisError> {
+        assert_eq!(self.constants.len(), MIMC_ROUNDS);
+
+        // Allocate the first component of the preimage.
+        let mut xl_value = self.xl;
+        let mut xl = cs.alloc(
+            || "preimage xl",
+            || xl_value.ok_or(SynthesisError::AssignmentMissing),
+        )?;
+
+        // Allocate the second component of the preimage.
+        let mut xr_value = self.xr;
+        let mut xr = cs.alloc(
+            || "preimage xr",
+            || xr_value.ok_or(SynthesisError::AssignmentMissing),
+        )?;
+
+        for i in 0..MIMC_ROUNDS {
+            // xL, xR := xR + (xL + Ci)^3, xL
+            let cs = &mut cs.namespace(|| format!("round {}", i));
+
+            // tmp = (xL + Ci)^2
+            let tmp_value = xl_value.map(|mut e| {
+                e.add_assign(&self.constants[i]);
+                e.square();
+                e
+            });
+            let tmp = cs.alloc(
+                || "tmp",
+                || tmp_value.ok_or(SynthesisError::AssignmentMissing),
+            )?;
+
+            cs.enforce(
+                || "tmp = (xL + Ci)^2",
+                |lc| lc + xl + (self.constants[i], CS::one()),
+                |lc| lc + xl + (self.constants[i], CS::one()),
+                |lc| lc + tmp,
+            );
+
+            // new_xL = xR + (xL + Ci)^3
+            // new_xL = xR + tmp * (xL + Ci)
+            // new_xL - xR = tmp * (xL + Ci)
+            let new_xl_value = xl_value.map(|mut e| {
+                e.add_assign(&self.constants[i]);
+                e.mul_assign(&tmp_value.unwrap());
+                e.add_assign(&xr_value.unwrap());
+                e
+            });
+
+            let new_xl = if i == (MIMC_ROUNDS - 1) {
+                // This is the last round, xL is our image and so
+                // we allocate a public input.
+                cs.alloc_input(
+                    || "image",
+                    || new_xl_value.ok_or(SynthesisError::AssignmentMissing),
+                )?
+            } else {
+                cs.alloc(
+                    || "new_xl",
+                    || new_xl_value.ok_or(SynthesisError::AssignmentMissing),
+                )?
+            };
+
+            cs.enforce(
+                || "new_xL = xR + (xL + Ci)^3",
+                |lc| lc + tmp,
+                |lc| lc + xl + (self.constants[i], CS::one()),
+                |lc| lc + new_xl - xr,
+            );
+
+            // xR = xL
+            xr = xl;
+            xr_value = xl_value;
+
+            // xL = new_xL
+            xl = new_xl;
+            xl_value = new_xl_value;
+        }
+
+        Ok(())
+    }
+}
+
+#[test]
+fn test_mimc() {
+    // This may not be cryptographically safe, use
+    // `OsRng` (for example) in production software.
+    let rng = &mut thread_rng();
+
+    // Generate the MiMC round constants
+    let constants = (0..MIMC_ROUNDS)
+        .map(|_| <Bls12 as ScalarEngine>::Fr::random(rng))
+        .collect::<Vec<_>>();
+
+    println!("Creating parameters...");
+
+    // Create parameters for our circuit
+    let params = {
+        let c = MiMCDemo::<Bls12> {
+            xl: None,
+            xr: None,
+            constants: &constants,
+        };
+
+        generate_random_parameters(c, rng).unwrap()
+    };
+
+    // Prepare the verification key (for proof verification)
+    let pvk = prepare_verifying_key(&params.vk);
+
+    println!("Creating proofs...");
+
+    // Let's benchmark stuff!
+    const SAMPLES: u32 = 50;
+    let mut total_proving = Duration::new(0, 0);
+    let mut total_verifying = Duration::new(0, 0);
+
+    // Just a place to put the proof data, so we can
+    // benchmark deserialization.
+    let mut proof_vec = vec![];
+
+    for _ in 0..SAMPLES {
+        // Generate a random preimage and compute the image
+        let xl = <Bls12 as ScalarEngine>::Fr::random(rng);
+        let xr = <Bls12 as ScalarEngine>::Fr::random(rng);
+        let image = mimc::<Bls12>(xl, xr, &constants);
+
+        proof_vec.truncate(0);
+
+        let start = Instant::now();
+        {
+            // Create an instance of our circuit (with the
+            // witness)
+            let c = MiMCDemo {
+                xl: Some(xl),
+                xr: Some(xr),
+                constants: &constants,
+            };
+
+            // Create a groth16 proof with our parameters.
+            let proof = create_random_proof(c, &params, rng).unwrap();
+
+            proof.write(&mut proof_vec).unwrap();
+        }
+
+        total_proving += start.elapsed();
+
+        let start = Instant::now();
+        let proof = Proof::read(&proof_vec[..]).unwrap();
+        // Check the proof
+        assert!(verify_proof(&pvk, &proof, &[image]).unwrap());
+        total_verifying += start.elapsed();
+    }
+    let proving_avg = total_proving / SAMPLES;
+    let proving_avg =
+        proving_avg.subsec_nanos() as f64 / 1_000_000_000f64 + (proving_avg.as_secs() as f64);
+
+    let verifying_avg = total_verifying / SAMPLES;
+    let verifying_avg =
+        verifying_avg.subsec_nanos() as f64 / 1_000_000_000f64 + (verifying_avg.as_secs() as f64);
+
+    println!("Average proving time: {:?} seconds", proving_avg);
+    println!("Average verifying time: {:?} seconds", verifying_avg);
+}

ff/.gitignore

@@ -0,0 +1,3 @@
+target/
+**/*.rs.bk
+Cargo.lock

ff/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "ff"
+version = "0.5.2"
+authors = ["Sean Bowe <ewillbefull@gmail.com>"]
+description = "Library for building and interfacing with finite fields"
+readme = "README.md"
+documentation = "https://docs.rs/ff/"
+homepage = "https://github.com/ebfull/ff"
+license = "MIT/Apache-2.0"
+repository = "https://github.com/ebfull/ff"
+edition = "2018"
+
+[dependencies]
+byteorder = "1"
+ff_derive = { version = "^0.4.1", path = "ff_derive", optional = true }
+rand_core = "0.5"
+
+[features]
+default = []
+derive = ["ff_derive"]
+
+[badges]
+maintenance = { status = "actively-developed" }

ff/LICENSE-APACHE

@@ -0,0 +1,202 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
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+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
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+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
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+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
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+   file or class name and description of purpose be included on the
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+Copyright [yyyy] [name of copyright owner]
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
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+
+Unless required by applicable law or agreed to in writing, software
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+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+

ff/LICENSE-MIT

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2017 Sean Bowe
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

ff/README.md

@@ -0,0 +1,67 @@
+# ff
+
+`ff` is a finite field library written in pure Rust, with no `unsafe{}` code.
+
+## Disclaimers
+
+* This library does not provide constant-time guarantees.
+
+## Usage
+
+Add the `ff` crate to your `Cargo.toml`:
+
+```toml
+[dependencies]
+ff = "0.5"
+```
+
+The `ff` crate contains `Field`, `PrimeField`, `PrimeFieldRepr` and `SqrtField` traits.
+See the **[documentation](https://docs.rs/ff/)** for more.
+
+### #![derive(PrimeField)]
+
+If you need an implementation of a prime field, this library also provides a procedural
+macro that will expand into an efficient implementation of a prime field when supplied
+with the modulus. `PrimeFieldGenerator` must be an element of Fp of p-1 order, that is
+also quadratic nonresidue.
+
+First, enable the `derive` crate feature:
+
+```toml
+[dependencies]
+ff = { version = "0.4", features = ["derive"] }
+```
+
+And then use the macro like so:
+
+```rust
+extern crate rand;
+#[macro_use]
+extern crate ff;
+
+#[derive(PrimeField)]
+#[PrimeFieldModulus = "52435875175126190479447740508185965837690552500527637822603658699938581184513"]
+#[PrimeFieldGenerator = "7"]
+struct Fp(FpRepr);
+```
+
+And that's it! `Fp` now implements `Field` and `PrimeField`. `Fp` will also implement
+`SqrtField` if supported. The library implements `FpRepr` itself and derives
+`PrimeFieldRepr` for it.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

ff/ff_derive/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "ff_derive"
+version = "0.4.1"
+authors = ["Sean Bowe <ewillbefull@gmail.com>"]
+description = "Procedural macro library used to build custom prime field implementations"
+documentation = "https://docs.rs/ff/"
+homepage = "https://github.com/ebfull/ff"
+license = "MIT/Apache-2.0"
+repository = "https://github.com/ebfull/ff"
+edition = "2018"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+num-bigint = "0.2"
+num-traits = "0.2"
+num-integer = "0.1"
+proc-macro2 = "1"
+quote = "1"
+syn = "1"
+
+[badges]
+maintenance = { status = "passively-maintained" }

ff/src/lib.rs

@@ -0,0 +1,393 @@
+//! This crate provides traits for working with finite fields.
+
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+#![allow(unused_imports)]
+
+#[cfg(feature = "derive")]
+pub use ff_derive::*;
+
+use rand_core::RngCore;
+use std::error::Error;
+use std::fmt;
+use std::io::{self, Read, Write};
+
+/// This trait represents an element of a field.
+pub trait Field:
+    Sized + Eq + Copy + Clone + Send + Sync + fmt::Debug + fmt::Display + 'static
+{
+    /// Returns an element chosen uniformly at random using a user-provided RNG.
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self;
+
+    /// Returns the zero element of the field, the additive identity.
+    fn zero() -> Self;
+
+    /// Returns the one element of the field, the multiplicative identity.
+    fn one() -> Self;
+
+    /// Returns true iff this element is zero.
+    fn is_zero(&self) -> bool;
+
+    /// Squares this element.
+    fn square(&mut self);
+
+    /// Doubles this element.
+    fn double(&mut self);
+
+    /// Negates this element.
+    fn negate(&mut self);
+
+    /// Adds another element to this element.
+    fn add_assign(&mut self, other: &Self);
+
+    /// Subtracts another element from this element.
+    fn sub_assign(&mut self, other: &Self);
+
+    /// Multiplies another element by this element.
+    fn mul_assign(&mut self, other: &Self);
+
+    /// Computes the multiplicative inverse of this element, if nonzero.
+    fn inverse(&self) -> Option<Self>;
+
+    /// Exponentiates this element by a power of the base prime modulus via
+    /// the Frobenius automorphism.
+    fn frobenius_map(&mut self, power: usize);
+
+    /// Exponentiates this element by a number represented with `u64` limbs,
+    /// least significant digit first.
+    fn pow<S: AsRef<[u64]>>(&self, exp: S) -> Self {
+        let mut res = Self::one();
+
+        let mut found_one = false;
+
+        for i in BitIterator::new(exp) {
+            if found_one {
+                res.square();
+            } else {
+                found_one = i;
+            }
+
+            if i {
+                res.mul_assign(self);
+            }
+        }
+
+        res
+    }
+}
+
+/// This trait represents an element of a field that has a square root operation described for it.
+pub trait SqrtField: Field {
+    /// Returns the Legendre symbol of the field element.
+    fn legendre(&self) -> LegendreSymbol;
+
+    /// Returns the square root of the field element, if it is
+    /// quadratic residue.
+    fn sqrt(&self) -> Option<Self>;
+}
+
+/// This trait represents a wrapper around a biginteger which can encode any element of a particular
+/// prime field. It is a smart wrapper around a sequence of `u64` limbs, least-significant digit
+/// first.
+pub trait PrimeFieldRepr:
+    Sized
+    + Copy
+    + Clone
+    + Eq
+    + Ord
+    + Send
+    + Sync
+    + Default
+    + fmt::Debug
+    + fmt::Display
+    + 'static
+    + AsRef<[u64]>
+    + AsMut<[u64]>
+    + From<u64>
+{
+    /// Subtract another represetation from this one.
+    fn sub_noborrow(&mut self, other: &Self);
+
+    /// Add another representation to this one.
+    fn add_nocarry(&mut self, other: &Self);
+
+    /// Compute the number of bits needed to encode this number. Always a
+    /// multiple of 64.
+    fn num_bits(&self) -> u32;
+
+    /// Returns true iff this number is zero.
+    fn is_zero(&self) -> bool;
+
+    /// Returns true iff this number is odd.
+    fn is_odd(&self) -> bool;
+
+    /// Returns true iff this number is even.
+    fn is_even(&self) -> bool;
+
+    /// Performs a rightwise bitshift of this number, effectively dividing
+    /// it by 2.
+    fn div2(&mut self);
+
+    /// Performs a rightwise bitshift of this number by some amount.
+    fn shr(&mut self, amt: u32);
+
+    /// Performs a leftwise bitshift of this number, effectively multiplying
+    /// it by 2. Overflow is ignored.
+    fn mul2(&mut self);
+
+    /// Performs a leftwise bitshift of this number by some amount.
+    fn shl(&mut self, amt: u32);
+
+    /// Writes this `PrimeFieldRepr` as a big endian integer.
+    fn write_be<W: Write>(&self, mut writer: W) -> io::Result<()> {
+        use byteorder::{BigEndian, WriteBytesExt};
+
+        for digit in self.as_ref().iter().rev() {
+            writer.write_u64::<BigEndian>(*digit)?;
+        }
+
+        Ok(())
+    }
+
+    /// Reads a big endian integer into this representation.
+    fn read_be<R: Read>(&mut self, mut reader: R) -> io::Result<()> {
+        use byteorder::{BigEndian, ReadBytesExt};
+
+        for digit in self.as_mut().iter_mut().rev() {
+            *digit = reader.read_u64::<BigEndian>()?;
+        }
+
+        Ok(())
+    }
+
+    /// Writes this `PrimeFieldRepr` as a little endian integer.
+    fn write_le<W: Write>(&self, mut writer: W) -> io::Result<()> {
+        use byteorder::{LittleEndian, WriteBytesExt};
+
+        for digit in self.as_ref().iter() {
+            writer.write_u64::<LittleEndian>(*digit)?;
+        }
+
+        Ok(())
+    }
+
+    /// Reads a little endian integer into this representation.
+    fn read_le<R: Read>(&mut self, mut reader: R) -> io::Result<()> {
+        use byteorder::{LittleEndian, ReadBytesExt};
+
+        for digit in self.as_mut().iter_mut() {
+            *digit = reader.read_u64::<LittleEndian>()?;
+        }
+
+        Ok(())
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum LegendreSymbol {
+    Zero = 0,
+    QuadraticResidue = 1,
+    QuadraticNonResidue = -1,
+}
+
+/// An error that may occur when trying to interpret a `PrimeFieldRepr` as a
+/// `PrimeField` element.
+#[derive(Debug)]
+pub enum PrimeFieldDecodingError {
+    /// The encoded value is not in the field
+    NotInField(String),
+}
+
+impl Error for PrimeFieldDecodingError {
+    fn description(&self) -> &str {
+        match *self {
+            PrimeFieldDecodingError::NotInField(..) => "not an element of the field",
+        }
+    }
+}
+
+impl fmt::Display for PrimeFieldDecodingError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        match *self {
+            PrimeFieldDecodingError::NotInField(ref repr) => {
+                write!(f, "{} is not an element of the field", repr)
+            }
+        }
+    }
+}
+
+/// This represents an element of a prime field.
+pub trait PrimeField: Field {
+    /// The prime field can be converted back and forth into this biginteger
+    /// representation.
+    type Repr: PrimeFieldRepr + From<Self>;
+
+    /// Interpret a string of numbers as a (congruent) prime field element.
+    /// Does not accept unnecessary leading zeroes or a blank string.
+    fn from_str(s: &str) -> Option<Self> {
+        if s.is_empty() {
+            return None;
+        }
+
+        if s == "0" {
+            return Some(Self::zero());
+        }
+
+        let mut res = Self::zero();
+
+        let ten = Self::from_repr(Self::Repr::from(10)).unwrap();
+
+        let mut first_digit = true;
+
+        for c in s.chars() {
+            match c.to_digit(10) {
+                Some(c) => {
+                    if first_digit {
+                        if c == 0 {
+                            return None;
+                        }
+
+                        first_digit = false;
+                    }
+
+                    res.mul_assign(&ten);
+                    res.add_assign(&Self::from_repr(Self::Repr::from(u64::from(c))).unwrap());
+                }
+                None => {
+                    return None;
+                }
+            }
+        }
+
+        Some(res)
+    }
+
+    /// Convert this prime field element into a biginteger representation.
+    fn from_repr(_: Self::Repr) -> Result<Self, PrimeFieldDecodingError>;
+
+    /// Convert a biginteger representation into a prime field element, if
+    /// the number is an element of the field.
+    fn into_repr(&self) -> Self::Repr;
+
+    /// Returns the field characteristic; the modulus.
+    fn char() -> Self::Repr;
+
+    /// How many bits are needed to represent an element of this field.
+    const NUM_BITS: u32;
+
+    /// How many bits of information can be reliably stored in the field element.
+    const CAPACITY: u32;
+
+    /// Returns the multiplicative generator of `char()` - 1 order. This element
+    /// must also be quadratic nonresidue.
+    fn multiplicative_generator() -> Self;
+
+    /// 2^s * t = `char()` - 1 with t odd.
+    const S: u32;
+
+    /// Returns the 2^s root of unity computed by exponentiating the `multiplicative_generator()`
+    /// by t.
+    fn root_of_unity() -> Self;
+}
+
+/// An "engine" is a collection of types (fields, elliptic curve groups, etc.)
+/// with well-defined relationships. Specific relationships (for example, a
+/// pairing-friendly curve) can be defined in a subtrait.
+pub trait ScalarEngine: Sized + 'static + Clone {
+    /// This is the scalar field of the engine's groups.
+    type Fr: PrimeField + SqrtField;
+}
+
+#[derive(Debug)]
+pub struct BitIterator<E> {
+    t: E,
+    n: usize,
+}
+
+impl<E: AsRef<[u64]>> BitIterator<E> {
+    pub fn new(t: E) -> Self {
+        let n = t.as_ref().len() * 64;
+
+        BitIterator { t, n }
+    }
+}
+
+impl<E: AsRef<[u64]>> Iterator for BitIterator<E> {
+    type Item = bool;
+
+    fn next(&mut self) -> Option<bool> {
+        if self.n == 0 {
+            None
+        } else {
+            self.n -= 1;
+            let part = self.n / 64;
+            let bit = self.n - (64 * part);
+
+            Some(self.t.as_ref()[part] & (1 << bit) > 0)
+        }
+    }
+}
+
+#[test]
+fn test_bit_iterator() {
+    let mut a = BitIterator::new([0xa953d79b83f6ab59, 0x6dea2059e200bd39]);
+    let expected = "01101101111010100010000001011001111000100000000010111101001110011010100101010011110101111001101110000011111101101010101101011001";
+
+    for e in expected.chars() {
+        assert!(a.next().unwrap() == (e == '1'));
+    }
+
+    assert!(a.next().is_none());
+
+    let expected = "1010010101111110101010000101101011101000011101110101001000011001100100100011011010001011011011010001011011101100110100111011010010110001000011110100110001100110011101101000101100011100100100100100001010011101010111110011101011000011101000111011011101011001";
+
+    let mut a = BitIterator::new([
+        0x429d5f3ac3a3b759,
+        0xb10f4c66768b1c92,
+        0x92368b6d16ecd3b4,
+        0xa57ea85ae8775219,
+    ]);
+
+    for e in expected.chars() {
+        assert!(a.next().unwrap() == (e == '1'));
+    }
+
+    assert!(a.next().is_none());
+}
+
+pub use self::arith_impl::*;
+
+mod arith_impl {
+    /// Calculate a - b - borrow, returning the result and modifying
+    /// the borrow value.
+    #[inline(always)]
+    pub fn sbb(a: u64, b: u64, borrow: &mut u64) -> u64 {
+        let tmp = (1u128 << 64) + u128::from(a) - u128::from(b) - u128::from(*borrow);
+
+        *borrow = if tmp >> 64 == 0 { 1 } else { 0 };
+
+        tmp as u64
+    }
+
+    /// Calculate a + b + carry, returning the sum and modifying the
+    /// carry value.
+    #[inline(always)]
+    pub fn adc(a: u64, b: u64, carry: &mut u64) -> u64 {
+        let tmp = u128::from(a) + u128::from(b) + u128::from(*carry);
+
+        *carry = (tmp >> 64) as u64;
+
+        tmp as u64
+    }
+
+    /// Calculate a + (b * c) + carry, returning the least significant digit
+    /// and setting carry to the most significant digit.
+    #[inline(always)]
+    pub fn mac_with_carry(a: u64, b: u64, c: u64, carry: &mut u64) -> u64 {
+        let tmp = (u128::from(a)) + u128::from(b) * u128::from(c) + u128::from(*carry);
+
+        *carry = (tmp >> 64) as u64;
+
+        tmp as u64
+    }
+}

group/.gitignore

@@ -0,0 +1,3 @@
+/target
+**/*.rs.bk
+Cargo.lock

group/COPYRIGHT

@@ -0,0 +1,14 @@
+Copyrights in the "group" library are retained by their contributors. No
+copyright assignment is required to contribute to the "group" library.
+
+The "group" library is licensed under either of
+
+ * Apache License, Version 2.0, (see ./LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license (see ./LICENSE-MIT or http://opensource.org/licenses/MIT)
+
+at your option.
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

group/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "group"
+version = "0.2.0"
+authors = [
+    "Sean Bowe <ewillbefull@gmail.com>",
+    "Jack Grigg <jack@z.cash>",
+]
+readme = "README.md"
+license = "MIT/Apache-2.0"
+
+description = "Elliptic curve group traits and utilities"
+documentation = "https://docs.rs/group/"
+homepage = "https://github.com/ebfull/group"
+repository = "https://github.com/ebfull/group"
+edition = "2018"
+
+[dependencies]
+ff = { version = "0.5.0", path = "../ff" }
+rand = "0.7"
+rand_xorshift = "0.2"
+
+[badges]
+maintenance = { status = "actively-developed" }

group/LICENSE-APACHE

@@ -0,0 +1,201 @@
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+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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+Unless required by applicable law or agreed to in writing, software
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+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

group/LICENSE-MIT

@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
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+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

group/README.md

@@ -0,0 +1,20 @@
+# group [![Crates.io](https://img.shields.io/crates/v/group.svg)](https://crates.io/crates/group) #
+
+`group` is a crate for working with groups over elliptic curves.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

group/src/lib.rs

@@ -0,0 +1,190 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
+use ff::{PrimeField, PrimeFieldDecodingError, ScalarEngine, SqrtField};
+use rand::RngCore;
+use std::error::Error;
+use std::fmt;
+
+pub mod tests;
+
+mod wnaf;
+pub use self::wnaf::Wnaf;
+
+/// Projective representation of an elliptic curve point guaranteed to be
+/// in the correct prime order subgroup.
+pub trait CurveProjective:
+    PartialEq + Eq + Sized + Copy + Clone + Send + Sync + fmt::Debug + fmt::Display + 'static
+{
+    type Engine: ScalarEngine<Fr = Self::Scalar>;
+    type Scalar: PrimeField + SqrtField;
+    type Base: SqrtField;
+    type Affine: CurveAffine<Projective = Self, Scalar = Self::Scalar>;
+
+    /// Returns an element chosen uniformly at random using a user-provided RNG.
+    fn random<R: RngCore>(rng: &mut R) -> Self;
+
+    /// Returns the additive identity.
+    fn zero() -> Self;
+
+    /// Returns a fixed generator of unknown exponent.
+    fn one() -> Self;
+
+    /// Determines if this point is the point at infinity.
+    fn is_zero(&self) -> bool;
+
+    /// Normalizes a slice of projective elements so that
+    /// conversion to affine is cheap.
+    fn batch_normalization(v: &mut [Self]);
+
+    /// Checks if the point is already "normalized" so that
+    /// cheap affine conversion is possible.
+    fn is_normalized(&self) -> bool;
+
+    /// Doubles this element.
+    fn double(&mut self);
+
+    /// Adds another element to this element.
+    fn add_assign(&mut self, other: &Self);
+
+    /// Subtracts another element from this element.
+    fn sub_assign(&mut self, other: &Self) {
+        let mut tmp = *other;
+        tmp.negate();
+        self.add_assign(&tmp);
+    }
+
+    /// Adds an affine element to this element.
+    fn add_assign_mixed(&mut self, other: &Self::Affine);
+
+    /// Negates this element.
+    fn negate(&mut self);
+
+    /// Performs scalar multiplication of this element.
+    fn mul_assign<S: Into<<Self::Scalar as PrimeField>::Repr>>(&mut self, other: S);
+
+    /// Converts this element into its affine representation.
+    fn into_affine(&self) -> Self::Affine;
+
+    /// Recommends a wNAF window table size given a scalar. Always returns a number
+    /// between 2 and 22, inclusive.
+    fn recommended_wnaf_for_scalar(scalar: <Self::Scalar as PrimeField>::Repr) -> usize;
+
+    /// Recommends a wNAF window size given the number of scalars you intend to multiply
+    /// a base by. Always returns a number between 2 and 22, inclusive.
+    fn recommended_wnaf_for_num_scalars(num_scalars: usize) -> usize;
+}
+
+/// Affine representation of an elliptic curve point guaranteed to be
+/// in the correct prime order subgroup.
+pub trait CurveAffine:
+    Copy + Clone + Sized + Send + Sync + fmt::Debug + fmt::Display + PartialEq + Eq + 'static
+{
+    type Engine: ScalarEngine<Fr = Self::Scalar>;
+    type Scalar: PrimeField + SqrtField;
+    type Base: SqrtField;
+    type Projective: CurveProjective<Affine = Self, Scalar = Self::Scalar>;
+    type Uncompressed: EncodedPoint<Affine = Self>;
+    type Compressed: EncodedPoint<Affine = Self>;
+
+    /// Returns the additive identity.
+    fn zero() -> Self;
+
+    /// Returns a fixed generator of unknown exponent.
+    fn one() -> Self;
+
+    /// Determines if this point represents the point at infinity; the
+    /// additive identity.
+    fn is_zero(&self) -> bool;
+
+    /// Negates this element.
+    fn negate(&mut self);
+
+    /// Performs scalar multiplication of this element with mixed addition.
+    fn mul<S: Into<<Self::Scalar as PrimeField>::Repr>>(&self, other: S) -> Self::Projective;
+
+    /// Converts this element into its affine representation.
+    fn into_projective(&self) -> Self::Projective;
+
+    /// Converts this element into its compressed encoding, so long as it's not
+    /// the point at infinity.
+    fn into_compressed(&self) -> Self::Compressed {
+        <Self::Compressed as EncodedPoint>::from_affine(*self)
+    }
+
+    /// Converts this element into its uncompressed encoding, so long as it's not
+    /// the point at infinity.
+    fn into_uncompressed(&self) -> Self::Uncompressed {
+        <Self::Uncompressed as EncodedPoint>::from_affine(*self)
+    }
+}
+
+/// An encoded elliptic curve point, which should essentially wrap a `[u8; N]`.
+pub trait EncodedPoint:
+    Sized + Send + Sync + AsRef<[u8]> + AsMut<[u8]> + Clone + Copy + 'static
+{
+    type Affine: CurveAffine;
+
+    /// Creates an empty representation.
+    fn empty() -> Self;
+
+    /// Returns the number of bytes consumed by this representation.
+    fn size() -> usize;
+
+    /// Converts an `EncodedPoint` into a `CurveAffine` element,
+    /// if the encoding represents a valid element.
+    fn into_affine(&self) -> Result<Self::Affine, GroupDecodingError>;
+
+    /// Converts an `EncodedPoint` into a `CurveAffine` element,
+    /// without guaranteeing that the encoding represents a valid
+    /// element. This is useful when the caller knows the encoding is
+    /// valid already.
+    ///
+    /// If the encoding is invalid, this can break API invariants,
+    /// so caution is strongly encouraged.
+    fn into_affine_unchecked(&self) -> Result<Self::Affine, GroupDecodingError>;
+
+    /// Creates an `EncodedPoint` from an affine point, as long as the
+    /// point is not the point at infinity.
+    fn from_affine(affine: Self::Affine) -> Self;
+}
+
+/// An error that may occur when trying to decode an `EncodedPoint`.
+#[derive(Debug)]
+pub enum GroupDecodingError {
+    /// The coordinate(s) do not lie on the curve.
+    NotOnCurve,
+    /// The element is not part of the r-order subgroup.
+    NotInSubgroup,
+    /// One of the coordinates could not be decoded
+    CoordinateDecodingError(&'static str, PrimeFieldDecodingError),
+    /// The compression mode of the encoded element was not as expected
+    UnexpectedCompressionMode,
+    /// The encoding contained bits that should not have been set
+    UnexpectedInformation,
+}
+
+impl Error for GroupDecodingError {
+    fn description(&self) -> &str {
+        match *self {
+            GroupDecodingError::NotOnCurve => "coordinate(s) do not lie on the curve",
+            GroupDecodingError::NotInSubgroup => "the element is not part of an r-order subgroup",
+            GroupDecodingError::CoordinateDecodingError(..) => "coordinate(s) could not be decoded",
+            GroupDecodingError::UnexpectedCompressionMode => {
+                "encoding has unexpected compression mode"
+            }
+            GroupDecodingError::UnexpectedInformation => "encoding has unexpected information",
+        }
+    }
+}
+
+impl fmt::Display for GroupDecodingError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        match *self {
+            GroupDecodingError::CoordinateDecodingError(description, ref err) => {
+                write!(f, "{} decoding error: {}", description, err)
+            }
+            _ => write!(f, "{}", self.description()),
+        }
+    }
+}

group/src/tests/mod.rs

@@ -0,0 +1,449 @@
+use ff::{Field, PrimeField};
+use rand::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use crate::{CurveAffine, CurveProjective, EncodedPoint};
+
+pub fn curve_tests<G: CurveProjective>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    // Negation edge case with zero.
+    {
+        let mut z = G::zero();
+        z.negate();
+        assert!(z.is_zero());
+    }
+
+    // Doubling edge case with zero.
+    {
+        let mut z = G::zero();
+        z.double();
+        assert!(z.is_zero());
+    }
+
+    // Addition edge cases with zero
+    {
+        let mut r = G::random(&mut rng);
+        let rcopy = r;
+        r.add_assign(&G::zero());
+        assert_eq!(r, rcopy);
+        r.add_assign_mixed(&G::Affine::zero());
+        assert_eq!(r, rcopy);
+
+        let mut z = G::zero();
+        z.add_assign(&G::zero());
+        assert!(z.is_zero());
+        z.add_assign_mixed(&G::Affine::zero());
+        assert!(z.is_zero());
+
+        let mut z2 = z;
+        z2.add_assign(&r);
+
+        z.add_assign_mixed(&r.into_affine());
+
+        assert_eq!(z, z2);
+        assert_eq!(z, r);
+    }
+
+    // Transformations
+    {
+        let a = G::random(&mut rng);
+        let b = a.into_affine().into_projective();
+        let c = a
+            .into_affine()
+            .into_projective()
+            .into_affine()
+            .into_projective();
+        assert_eq!(a, b);
+        assert_eq!(b, c);
+    }
+
+    random_addition_tests::<G>();
+    random_multiplication_tests::<G>();
+    random_doubling_tests::<G>();
+    random_negation_tests::<G>();
+    random_transformation_tests::<G>();
+    random_wnaf_tests::<G>();
+    random_encoding_tests::<G::Affine>();
+}
+
+fn random_wnaf_tests<G: CurveProjective>() {
+    use crate::wnaf::*;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    {
+        let mut table = vec![];
+        let mut wnaf = vec![];
+
+        for w in 2..14 {
+            for _ in 0..100 {
+                let g = G::random(&mut rng);
+                let s = G::Scalar::random(&mut rng).into_repr();
+                let mut g1 = g;
+                g1.mul_assign(s);
+
+                wnaf_table(&mut table, g, w);
+                wnaf_form(&mut wnaf, s, w);
+                let g2 = wnaf_exp(&table, &wnaf);
+
+                assert_eq!(g1, g2);
+            }
+        }
+    }
+
+    {
+        fn only_compiles_if_send<S: Send>(_: &S) {}
+
+        for _ in 0..100 {
+            let g = G::random(&mut rng);
+            let s = G::Scalar::random(&mut rng).into_repr();
+            let mut g1 = g;
+            g1.mul_assign(s);
+
+            let g2 = {
+                let mut wnaf = Wnaf::new();
+                wnaf.base(g, 1).scalar(s)
+            };
+            let g3 = {
+                let mut wnaf = Wnaf::new();
+                wnaf.scalar(s).base(g)
+            };
+            let g4 = {
+                let mut wnaf = Wnaf::new();
+                let mut shared = wnaf.base(g, 1).shared();
+
+                only_compiles_if_send(&shared);
+
+                shared.scalar(s)
+            };
+            let g5 = {
+                let mut wnaf = Wnaf::new();
+                let mut shared = wnaf.scalar(s).shared();
+
+                only_compiles_if_send(&shared);
+
+                shared.base(g)
+            };
+
+            let g6 = {
+                let mut wnaf = Wnaf::new();
+                {
+                    // Populate the vectors.
+                    wnaf.base(G::random(&mut rng), 1)
+                        .scalar(G::Scalar::random(&mut rng).into_repr());
+                }
+                wnaf.base(g, 1).scalar(s)
+            };
+            let g7 = {
+                let mut wnaf = Wnaf::new();
+                {
+                    // Populate the vectors.
+                    wnaf.base(G::random(&mut rng), 1)
+                        .scalar(G::Scalar::random(&mut rng).into_repr());
+                }
+                wnaf.scalar(s).base(g)
+            };
+            let g8 = {
+                let mut wnaf = Wnaf::new();
+                {
+                    // Populate the vectors.
+                    wnaf.base(G::random(&mut rng), 1)
+                        .scalar(G::Scalar::random(&mut rng).into_repr());
+                }
+                let mut shared = wnaf.base(g, 1).shared();
+
+                only_compiles_if_send(&shared);
+
+                shared.scalar(s)
+            };
+            let g9 = {
+                let mut wnaf = Wnaf::new();
+                {
+                    // Populate the vectors.
+                    wnaf.base(G::random(&mut rng), 1)
+                        .scalar(G::Scalar::random(&mut rng).into_repr());
+                }
+                let mut shared = wnaf.scalar(s).shared();
+
+                only_compiles_if_send(&shared);
+
+                shared.base(g)
+            };
+
+            assert_eq!(g1, g2);
+            assert_eq!(g1, g3);
+            assert_eq!(g1, g4);
+            assert_eq!(g1, g5);
+            assert_eq!(g1, g6);
+            assert_eq!(g1, g7);
+            assert_eq!(g1, g8);
+            assert_eq!(g1, g9);
+        }
+    }
+}
+
+fn random_negation_tests<G: CurveProjective>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let r = G::random(&mut rng);
+
+        let s = G::Scalar::random(&mut rng);
+        let mut sneg = s;
+        sneg.negate();
+
+        let mut t1 = r;
+        t1.mul_assign(s);
+
+        let mut t2 = r;
+        t2.mul_assign(sneg);
+
+        let mut t3 = t1;
+        t3.add_assign(&t2);
+        assert!(t3.is_zero());
+
+        let mut t4 = t1;
+        t4.add_assign_mixed(&t2.into_affine());
+        assert!(t4.is_zero());
+
+        t1.negate();
+        assert_eq!(t1, t2);
+    }
+}
+
+fn random_doubling_tests<G: CurveProjective>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let mut a = G::random(&mut rng);
+        let mut b = G::random(&mut rng);
+
+        // 2(a + b)
+        let mut tmp1 = a;
+        tmp1.add_assign(&b);
+        tmp1.double();
+
+        // 2a + 2b
+        a.double();
+        b.double();
+
+        let mut tmp2 = a;
+        tmp2.add_assign(&b);
+
+        let mut tmp3 = a;
+        tmp3.add_assign_mixed(&b.into_affine());
+
+        assert_eq!(tmp1, tmp2);
+        assert_eq!(tmp1, tmp3);
+    }
+}
+
+fn random_multiplication_tests<G: CurveProjective>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let mut a = G::random(&mut rng);
+        let mut b = G::random(&mut rng);
+        let a_affine = a.into_affine();
+        let b_affine = b.into_affine();
+
+        let s = G::Scalar::random(&mut rng);
+
+        // s ( a + b )
+        let mut tmp1 = a;
+        tmp1.add_assign(&b);
+        tmp1.mul_assign(s);
+
+        // sa + sb
+        a.mul_assign(s);
+        b.mul_assign(s);
+
+        let mut tmp2 = a;
+        tmp2.add_assign(&b);
+
+        // Affine multiplication
+        let mut tmp3 = a_affine.mul(s);
+        tmp3.add_assign(&b_affine.mul(s));
+
+        assert_eq!(tmp1, tmp2);
+        assert_eq!(tmp1, tmp3);
+    }
+}
+
+fn random_addition_tests<G: CurveProjective>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let a = G::random(&mut rng);
+        let b = G::random(&mut rng);
+        let c = G::random(&mut rng);
+        let a_affine = a.into_affine();
+        let b_affine = b.into_affine();
+        let c_affine = c.into_affine();
+
+        // a + a should equal the doubling
+        {
+            let mut aplusa = a;
+            aplusa.add_assign(&a);
+
+            let mut aplusamixed = a;
+            aplusamixed.add_assign_mixed(&a.into_affine());
+
+            let mut adouble = a;
+            adouble.double();
+
+            assert_eq!(aplusa, adouble);
+            assert_eq!(aplusa, aplusamixed);
+        }
+
+        let mut tmp = vec![G::zero(); 6];
+
+        // (a + b) + c
+        tmp[0] = a;
+        tmp[0].add_assign(&b);
+        tmp[0].add_assign(&c);
+
+        // a + (b + c)
+        tmp[1] = b;
+        tmp[1].add_assign(&c);
+        tmp[1].add_assign(&a);
+
+        // (a + c) + b
+        tmp[2] = a;
+        tmp[2].add_assign(&c);
+        tmp[2].add_assign(&b);
+
+        // Mixed addition
+
+        // (a + b) + c
+        tmp[3] = a_affine.into_projective();
+        tmp[3].add_assign_mixed(&b_affine);
+        tmp[3].add_assign_mixed(&c_affine);
+
+        // a + (b + c)
+        tmp[4] = b_affine.into_projective();
+        tmp[4].add_assign_mixed(&c_affine);
+        tmp[4].add_assign_mixed(&a_affine);
+
+        // (a + c) + b
+        tmp[5] = a_affine.into_projective();
+        tmp[5].add_assign_mixed(&c_affine);
+        tmp[5].add_assign_mixed(&b_affine);
+
+        // Comparisons
+        for i in 0..6 {
+            for j in 0..6 {
+                assert_eq!(tmp[i], tmp[j]);
+                assert_eq!(tmp[i].into_affine(), tmp[j].into_affine());
+            }
+
+            assert!(tmp[i] != a);
+            assert!(tmp[i] != b);
+            assert!(tmp[i] != c);
+
+            assert!(a != tmp[i]);
+            assert!(b != tmp[i]);
+            assert!(c != tmp[i]);
+        }
+    }
+}
+
+fn random_transformation_tests<G: CurveProjective>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let g = G::random(&mut rng);
+        let g_affine = g.into_affine();
+        let g_projective = g_affine.into_projective();
+        assert_eq!(g, g_projective);
+    }
+
+    // Batch normalization
+    for _ in 0..10 {
+        let mut v = (0..1000).map(|_| G::random(&mut rng)).collect::<Vec<_>>();
+
+        for i in &v {
+            assert!(!i.is_normalized());
+        }
+
+        use rand::distributions::{Distribution, Uniform};
+        let between = Uniform::new(0, 1000);
+        // Sprinkle in some normalized points
+        for _ in 0..5 {
+            v[between.sample(&mut rng)] = G::zero();
+        }
+        for _ in 0..5 {
+            let s = between.sample(&mut rng);
+            v[s] = v[s].into_affine().into_projective();
+        }
+
+        let expected_v = v
+            .iter()
+            .map(|v| v.into_affine().into_projective())
+            .collect::<Vec<_>>();
+        G::batch_normalization(&mut v);
+
+        for i in &v {
+            assert!(i.is_normalized());
+        }
+
+        assert_eq!(v, expected_v);
+    }
+}
+
+fn random_encoding_tests<G: CurveAffine>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    assert_eq!(
+        G::zero().into_uncompressed().into_affine().unwrap(),
+        G::zero()
+    );
+
+    assert_eq!(
+        G::zero().into_compressed().into_affine().unwrap(),
+        G::zero()
+    );
+
+    for _ in 0..1000 {
+        let mut r = G::Projective::random(&mut rng).into_affine();
+
+        let uncompressed = r.into_uncompressed();
+        let de_uncompressed = uncompressed.into_affine().unwrap();
+        assert_eq!(de_uncompressed, r);
+
+        let compressed = r.into_compressed();
+        let de_compressed = compressed.into_affine().unwrap();
+        assert_eq!(de_compressed, r);
+
+        r.negate();
+
+        let compressed = r.into_compressed();
+        let de_compressed = compressed.into_affine().unwrap();
+        assert_eq!(de_compressed, r);
+    }
+}

group/src/wnaf.rs

@@ -0,0 +1,181 @@
+use ff::{PrimeField, PrimeFieldRepr};
+
+use super::CurveProjective;
+
+/// Replaces the contents of `table` with a w-NAF window table for the given window size.
+pub(crate) fn wnaf_table<G: CurveProjective>(table: &mut Vec<G>, mut base: G, window: usize) {
+    table.truncate(0);
+    table.reserve(1 << (window - 1));
+
+    let mut dbl = base;
+    dbl.double();
+
+    for _ in 0..(1 << (window - 1)) {
+        table.push(base);
+        base.add_assign(&dbl);
+    }
+}
+
+/// Replaces the contents of `wnaf` with the w-NAF representation of a scalar.
+pub(crate) fn wnaf_form<S: PrimeFieldRepr>(wnaf: &mut Vec<i64>, mut c: S, window: usize) {
+    wnaf.truncate(0);
+
+    while !c.is_zero() {
+        let mut u;
+        if c.is_odd() {
+            u = (c.as_ref()[0] % (1 << (window + 1))) as i64;
+
+            if u > (1 << window) {
+                u -= 1 << (window + 1);
+            }
+
+            if u > 0 {
+                c.sub_noborrow(&S::from(u as u64));
+            } else {
+                c.add_nocarry(&S::from((-u) as u64));
+            }
+        } else {
+            u = 0;
+        }
+
+        wnaf.push(u);
+
+        c.div2();
+    }
+}
+
+/// Performs w-NAF exponentiation with the provided window table and w-NAF form scalar.
+///
+/// This function must be provided a `table` and `wnaf` that were constructed with
+/// the same window size; otherwise, it may panic or produce invalid results.
+pub(crate) fn wnaf_exp<G: CurveProjective>(table: &[G], wnaf: &[i64]) -> G {
+    let mut result = G::zero();
+
+    let mut found_one = false;
+
+    for n in wnaf.iter().rev() {
+        if found_one {
+            result.double();
+        }
+
+        if *n != 0 {
+            found_one = true;
+
+            if *n > 0 {
+                result.add_assign(&table[(n / 2) as usize]);
+            } else {
+                result.sub_assign(&table[((-n) / 2) as usize]);
+            }
+        }
+    }
+
+    result
+}
+
+/// A "w-ary non-adjacent form" exponentiation context.
+#[derive(Debug)]
+pub struct Wnaf<W, B, S> {
+    base: B,
+    scalar: S,
+    window_size: W,
+}
+
+impl<G: CurveProjective> Wnaf<(), Vec<G>, Vec<i64>> {
+    /// Construct a new wNAF context without allocating.
+    pub fn new() -> Self {
+        Wnaf {
+            base: vec![],
+            scalar: vec![],
+            window_size: (),
+        }
+    }
+
+    /// Given a base and a number of scalars, compute a window table and return a `Wnaf` object that
+    /// can perform exponentiations with `.scalar(..)`.
+    pub fn base(&mut self, base: G, num_scalars: usize) -> Wnaf<usize, &[G], &mut Vec<i64>> {
+        // Compute the appropriate window size based on the number of scalars.
+        let window_size = G::recommended_wnaf_for_num_scalars(num_scalars);
+
+        // Compute a wNAF table for the provided base and window size.
+        wnaf_table(&mut self.base, base, window_size);
+
+        // Return a Wnaf object that immutably borrows the computed base storage location,
+        // but mutably borrows the scalar storage location.
+        Wnaf {
+            base: &self.base[..],
+            scalar: &mut self.scalar,
+            window_size,
+        }
+    }
+
+    /// Given a scalar, compute its wNAF representation and return a `Wnaf` object that can perform
+    /// exponentiations with `.base(..)`.
+    pub fn scalar(
+        &mut self,
+        scalar: <<G as CurveProjective>::Scalar as PrimeField>::Repr,
+    ) -> Wnaf<usize, &mut Vec<G>, &[i64]> {
+        // Compute the appropriate window size for the scalar.
+        let window_size = G::recommended_wnaf_for_scalar(scalar);
+
+        // Compute the wNAF form of the scalar.
+        wnaf_form(&mut self.scalar, scalar, window_size);
+
+        // Return a Wnaf object that mutably borrows the base storage location, but
+        // immutably borrows the computed wNAF form scalar location.
+        Wnaf {
+            base: &mut self.base,
+            scalar: &self.scalar[..],
+            window_size,
+        }
+    }
+}
+
+impl<'a, G: CurveProjective> Wnaf<usize, &'a [G], &'a mut Vec<i64>> {
+    /// Constructs new space for the scalar representation while borrowing
+    /// the computed window table, for sending the window table across threads.
+    pub fn shared(&self) -> Wnaf<usize, &'a [G], Vec<i64>> {
+        Wnaf {
+            base: self.base,
+            scalar: vec![],
+            window_size: self.window_size,
+        }
+    }
+}
+
+impl<'a, G: CurveProjective> Wnaf<usize, &'a mut Vec<G>, &'a [i64]> {
+    /// Constructs new space for the window table while borrowing
+    /// the computed scalar representation, for sending the scalar representation
+    /// across threads.
+    pub fn shared(&self) -> Wnaf<usize, Vec<G>, &'a [i64]> {
+        Wnaf {
+            base: vec![],
+            scalar: self.scalar,
+            window_size: self.window_size,
+        }
+    }
+}
+
+impl<B, S: AsRef<[i64]>> Wnaf<usize, B, S> {
+    /// Performs exponentiation given a base.
+    pub fn base<G: CurveProjective>(&mut self, base: G) -> G
+    where
+        B: AsMut<Vec<G>>,
+    {
+        wnaf_table(self.base.as_mut(), base, self.window_size);
+        wnaf_exp(self.base.as_mut(), self.scalar.as_ref())
+    }
+}
+
+impl<B, S: AsMut<Vec<i64>>> Wnaf<usize, B, S> {
+    /// Performs exponentiation given a scalar.
+    pub fn scalar<G: CurveProjective>(
+        &mut self,
+        scalar: <<G as CurveProjective>::Scalar as PrimeField>::Repr,
+    ) -> G
+    where
+        B: AsRef<[G]>,
+    {
+        wnaf_form(self.scalar.as_mut(), scalar, self.window_size);
+        wnaf_exp(self.base.as_ref(), self.scalar.as_mut())
+    }
+}

librustzcash/Cargo.toml

@@ -0,0 +1,36 @@
+[package]
+name = "librustzcash"
+description = "Rust FFI used by the zcashd binary. Not an official API."
+version = "0.2.0"
+authors = [
+    "Sean Bowe <ewillbefull@gmail.com>",
+    "Jack Grigg <jack@z.cash>",
+    "Jay Graber <jay@z.cash>",
+    "Simon Liu <simon@z.cash>"
+]
+homepage = "https://github.com/zcash/librustzcash"
+repository = "https://github.com/zcash/librustzcash"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+edition = "2018"
+
+[lib]
+name = "rustzcash"
+path = "src/rustzcash.rs"
+crate-type = ["staticlib"]
+
+[dependencies]
+bellman = { version = "0.2.0", path = "../bellman" }
+blake2b_simd = "0.5"
+blake2s_simd = "0.5"
+ff = { version = "0.5.0", path = "../ff" }
+libc = "0.2"
+pairing = { version = "0.15.0", path = "../pairing" }
+lazy_static = "1"
+rand_core = "0.5.1"
+zcash_history = { version = "0.0.1", path = "../zcash_history" }
+zcash_primitives = { version = "0.1.0", path = "../zcash_primitives" }
+zcash_proofs = { version = "0.1.0", path = "../zcash_proofs" }
+
+[badges]
+maintenance = { status = "deprecated" }

librustzcash/README.md

@@ -0,0 +1,25 @@
+# librustzcash
+
+`librustzcash` is an FFI library crate that exposes the Zcash Rust components to
+the `zcashd` full node.
+
+The FFI API does not have any stability guarantees, and will change as required
+by `zcashd`.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](../LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](../LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.
+

librustzcash/include/librustzcash.h

@@ -4,6 +4,12 @@
 #include <stdint.h>
 
 extern "C" {
+#ifdef WIN32
+    typedef uint16_t codeunit;
+#else
+    typedef uint8_t codeunit;
+#endif
+
     void librustzcash_to_scalar(const unsigned char *input, unsigned char *result);
 
     void librustzcash_ask_to_ak(const unsigned char *ask, unsigned char *result);
@@ -19,11 +25,14 @@ extern "C" {
     /// Loads the zk-SNARK parameters into memory and saves
     /// paths as necessary. Only called once.
     void librustzcash_init_zksnark_params(
-        const char* spend_path,
+        const codeunit* spend_path,
+        size_t spend_path_len,
         const char* spend_hash,
-        const char* output_path,
+        const codeunit* output_path,
+        size_t output_path_len,
         const char* output_hash,
-        const char* sprout_path,
+        const codeunit* sprout_path,
+        size_t sprout_path_len,
         const char* sprout_hash
     );
 
@@ -103,8 +112,7 @@ extern "C" {
     bool librustzcash_sapling_output_proof(
         void *ctx,
         const unsigned char *esk,
-        const unsigned char *diversifier,
+        const unsigned char *payment_address,
-        const unsigned char *pk_d,
         const unsigned char *rcm,
         const uint64_t value,
         unsigned char *cv,
@@ -299,6 +307,33 @@ extern "C" {
         unsigned char *j_ret,
         unsigned char *addr_ret
     );
+
+    uint32_t librustzcash_mmr_append(
+        uint32_t cbranch,
+        uint32_t t_len,
+        const uint32_t *ni_ptr,
+        const unsigned char *n_ptr,
+        size_t p_len,
+        const unsigned char *nn_ptr,
+        unsigned char *rt_ret,
+        unsigned char *buf_ret
+    );
+
+    uint32_t librustzcash_mmr_delete(
+        uint32_t cbranch,
+        uint32_t t_len,
+        const uint32_t *ni_ptr,
+        const unsigned char *n_ptr,
+        size_t p_len,
+        size_t e_len,
+        unsigned char *rt_ret
+    );
+
+    uint32_t librustzcash_mmr_hash_node(
+        uint32_t cbranch,
+        const unsigned char *n_ptr,
+        unsigned char *h_ret
+    );
 }
 
 #endif // LIBRUSTZCASH_INCLUDE_H_

librustzcash/src/tests/key_agreement.rs

@@ -1,10 +1,10 @@
+use ff::{PrimeField, PrimeFieldRepr};
 use pairing::bls12_381::Bls12;
-use pairing::{PrimeField, PrimeFieldRepr};
+use rand_core::{OsRng, RngCore};
-use rand::{OsRng, Rng};
+use zcash_primitives::jubjub::{edwards, JubjubBls12};
-use sapling_crypto::jubjub::{edwards, JubjubBls12};
+use zcash_primitives::primitives::{Diversifier, ViewingKey};
-use sapling_crypto::primitives::{Diversifier, ViewingKey};
 
-use {
+use crate::{
     librustzcash_sapling_generate_r, librustzcash_sapling_ka_agree,
     librustzcash_sapling_ka_derivepublic,
 };
@@ -12,7 +12,7 @@ use {
 #[test]
 fn test_key_agreement() {
     let params = JubjubBls12::new();
-    let mut rng = OsRng::new().unwrap();
+    let mut rng = OsRng;
 
     // Create random viewing key
     let vk = ViewingKey::<Bls12> {
@@ -22,7 +22,9 @@ fn test_key_agreement() {
 
     // Create a random address with the viewing key
     let addr = loop {
-        match vk.into_payment_address(Diversifier(rng.gen()), &params) {
+        let mut d = [0; 11];
+        rng.fill_bytes(&mut d);
+        match vk.to_payment_address(Diversifier(d), &params) {
             Some(a) => break a,
             None => {}
         }
@@ -44,7 +46,7 @@ fn test_key_agreement() {
 
     // Serialize pk_d for the call to librustzcash_sapling_ka_agree
     let mut addr_pk_d = [0u8; 32];
-    addr.pk_d.write(&mut addr_pk_d[..]).unwrap();
+    addr.pk_d().write(&mut addr_pk_d[..]).unwrap();
 
     assert!(librustzcash_sapling_ka_agree(
         &addr_pk_d,
@@ -56,7 +58,7 @@ fn test_key_agreement() {
     // using the diversifier and esk.
     let mut epk = [0u8; 32];
     assert!(librustzcash_sapling_ka_derivepublic(
-        &addr.diversifier.0,
+        &addr.diversifier().0,
         &esk,
         &mut epk
     ));

librustzcash/src/tests/key_components.rs

@@ -1,12 +1,13 @@
-use pairing::{bls12_381::Bls12, PrimeField, PrimeFieldRepr};
+use ff::{PrimeField, PrimeFieldRepr};
-use sapling_crypto::{
+use pairing::bls12_381::Bls12;
+use zcash_primitives::{
     jubjub::{fs::FsRepr, FixedGenerators, JubjubEngine, JubjubParams},
     primitives::{Diversifier, ProofGenerationKey},
 };
 
 use super::JUBJUB;
 
-use {
+use crate::{
     librustzcash_ask_to_ak, librustzcash_check_diversifier, librustzcash_crh_ivk,
     librustzcash_ivk_to_pkd, librustzcash_nsk_to_nk,
 };
@@ -27,6 +28,8 @@ fn key_components() {
         note_v: u64,
         note_r: [u8; 32],
         note_cm: [u8; 32],
+        note_pos: u64,
+        note_nf: [u8; 32],
     };
 
     // From https://github.com/zcash-hackworks/zcash-test-vectors/blob/master/sapling_key_components.py
@@ -86,6 +89,12 @@ fn key_components() {
                 0x18, 0x50, 0xc9, 0xfe, 0xd4, 0x4f, 0xce, 0x08, 0x06, 0x27, 0x8f, 0x08, 0x3e, 0xf2,
                 0xdd, 0x07, 0x64, 0x39,
             ],
+            note_pos: 0,
+            note_nf: [
+                0x44, 0xfa, 0xd6, 0x56, 0x4f, 0xfd, 0xec, 0x9f, 0xa1, 0x9c, 0x43, 0xa2, 0x8f, 0x86,
+                0x1d, 0x5e, 0xbf, 0x60, 0x23, 0x46, 0x00, 0x7d, 0xe7, 0x62, 0x67, 0xd9, 0x75, 0x27,
+                0x47, 0xab, 0x40, 0x63,
+            ],
         },
         TestVector {
             sk: [
@@ -142,6 +151,12 @@ fn key_components() {
                 0x89, 0xe1, 0x0e, 0x26, 0x6b, 0xcf, 0xa3, 0x1c, 0x31, 0xb2, 0x9a, 0x53, 0xae, 0x72,
                 0xca, 0xd4, 0x69, 0x50,
             ],
+            note_pos: 763714296,
+            note_nf: [
+                0x67, 0x9e, 0xb0, 0xc3, 0xa7, 0x57, 0xe2, 0xae, 0x83, 0xcd, 0xb4, 0x2a, 0x1a, 0xb2,
+                0x59, 0xd7, 0x83, 0x88, 0x31, 0x54, 0x19, 0xad, 0xc7, 0x1d, 0x2e, 0x37, 0x63, 0x17,
+                0x4c, 0x2e, 0x9d, 0x93,
+            ],
         },
         TestVector {
             sk: [
@@ -198,6 +213,12 @@ fn key_components() {
                 0xb7, 0x40, 0x82, 0x96, 0x66, 0x17, 0x70, 0xb1, 0x01, 0xb0, 0xaa, 0x87, 0x83, 0x9f,
                 0x4e, 0x55, 0xf1, 0x51,
             ],
+            note_pos: 1527428592,
+            note_nf: [
+                0xe9, 0x8f, 0x6a, 0x8f, 0x34, 0xff, 0x49, 0x80, 0x59, 0xb3, 0xc7, 0x31, 0xb9, 0x1f,
+                0x45, 0x11, 0x08, 0xc4, 0x95, 0x4d, 0x91, 0x94, 0x84, 0x36, 0x1c, 0xf9, 0xb4, 0x8f,
+                0x59, 0xae, 0x1d, 0x14,
+            ],
         },
         TestVector {
             sk: [
@@ -254,6 +275,12 @@ fn key_components() {
                 0xbd, 0x10, 0x5d, 0x88, 0x39, 0x21, 0x2e, 0x0d, 0x16, 0x44, 0xb9, 0xd5, 0x5c, 0xaa,
                 0x60, 0xd1, 0x9b, 0x6c,
             ],
+            note_pos: 2291142888,
+            note_nf: [
+                0x55, 0x47, 0xaa, 0x12, 0xff, 0x80, 0xa6, 0xb3, 0x30, 0x4e, 0x3b, 0x05, 0x86, 0x56,
+                0x47, 0x2a, 0xbd, 0x2c, 0x81, 0x83, 0xb5, 0x9d, 0x07, 0x37, 0xb9, 0x3c, 0xee, 0x75,
+                0x8b, 0xec, 0x47, 0xa1,
+            ],
         },
         TestVector {
             sk: [
@@ -310,6 +337,12 @@ fn key_components() {
                 0xcf, 0x1e, 0x67, 0x15, 0xbf, 0xe7, 0x0b, 0x63, 0x2d, 0x04, 0x4b, 0x26, 0xfb, 0x2b,
                 0xc7, 0x1b, 0x7f, 0x36,
             ],
+            note_pos: 3054857184,
+            note_nf: [
+                0x8a, 0x9a, 0xbd, 0xa3, 0xd4, 0xef, 0x85, 0xca, 0xf2, 0x2b, 0xfa, 0xf2, 0xc4, 0x8f,
+                0x62, 0x38, 0x2a, 0x73, 0xa1, 0x62, 0x4e, 0xb8, 0xeb, 0x2b, 0xd0, 0x0d, 0x27, 0x03,
+                0x01, 0xbf, 0x3d, 0x13,
+            ],
         },
         TestVector {
             sk: [
@@ -366,6 +399,12 @@ fn key_components() {
                 0x1d, 0x74, 0xc5, 0xbc, 0xf2, 0xe1, 0xef, 0x95, 0x66, 0x90, 0x44, 0x73, 0x01, 0x69,
                 0xde, 0x1a, 0x5b, 0x4c,
             ],
+            note_pos: 3818571480,
+            note_nf: [
+                0x33, 0x2a, 0xd9, 0x9e, 0xb9, 0xe9, 0x77, 0xeb, 0x62, 0x7a, 0x12, 0x2d, 0xbf, 0xb2,
+                0xf2, 0x5f, 0xe5, 0x88, 0xe5, 0x97, 0x75, 0x3e, 0xc5, 0x58, 0x0f, 0xf2, 0xbe, 0x20,
+                0xb6, 0xc9, 0xa7, 0xe1,
+            ],
         },
         TestVector {
             sk: [
@@ -422,6 +461,12 @@ fn key_components() {
                 0x90, 0xb6, 0xe0, 0xf2, 0xf4, 0xbf, 0x4e, 0xc4, 0xa0, 0xdb, 0x5b, 0xbc, 0xcb, 0x5b,
                 0x78, 0x3a, 0x1e, 0x55,
             ],
+            note_pos: 287318480,
+            note_nf: [
+                0xfc, 0x74, 0xcd, 0x0e, 0x4b, 0xe0, 0x49, 0x57, 0xb1, 0x96, 0xcf, 0x87, 0x34, 0xae,
+                0x99, 0x23, 0x96, 0xaf, 0x4c, 0xfa, 0x8f, 0xec, 0xbb, 0x86, 0xf9, 0x61, 0xe6, 0xb4,
+                0x07, 0xd5, 0x1e, 0x11,
+            ],
         },
         TestVector {
             sk: [
@@ -478,6 +523,12 @@ fn key_components() {
                 0x60, 0xa0, 0x06, 0xf8, 0x2b, 0xb7, 0xad, 0xcd, 0x75, 0x22, 0x3f, 0xa8, 0x59, 0x36,
                 0xf7, 0x8c, 0x2b, 0x23,
             ],
+            note_pos: 1051032776,
+            note_nf: [
+                0xd2, 0xe8, 0x87, 0xbd, 0x85, 0x4a, 0x80, 0x2b, 0xce, 0x85, 0x70, 0x53, 0x02, 0x0f,
+                0x5d, 0x3e, 0x7c, 0x8a, 0xe5, 0x26, 0x7c, 0x5b, 0x65, 0x83, 0xb3, 0xd2, 0x12, 0xcc,
+                0x8b, 0xb6, 0x98, 0x90,
+            ],
         },
         TestVector {
             sk: [
@@ -534,6 +585,12 @@ fn key_components() {
                 0x23, 0x36, 0xc2, 0xa0, 0x5a, 0x08, 0x03, 0x23, 0x9b, 0x5b, 0x88, 0xfd, 0x92, 0x07,
                 0x8f, 0xea, 0x4d, 0x04,
             ],
+            note_pos: 1814747072,
+            note_nf: [
+                0xa8, 0x2f, 0x17, 0x50, 0xcc, 0x5b, 0x2b, 0xee, 0x64, 0x9a, 0x36, 0x5c, 0x04, 0x20,
+                0xed, 0x87, 0x07, 0x5b, 0x88, 0x71, 0xfd, 0xa4, 0xa7, 0xf5, 0x84, 0x0d, 0x6b, 0xbe,
+                0xb1, 0x7c, 0xd6, 0x20,
+            ],
         },
         TestVector {
             sk: [
@@ -590,6 +647,12 @@ fn key_components() {
                 0x64, 0x41, 0x9b, 0x0e, 0x55, 0x0a, 0xbb, 0xcb, 0x8e, 0x2b, 0xcb, 0xda, 0x8b, 0x63,
                 0xe4, 0x1d, 0xeb, 0x37,
             ],
+            note_pos: 2578461368,
+            note_nf: [
+                0x65, 0x36, 0x74, 0x87, 0x3b, 0x3c, 0x67, 0x0c, 0x58, 0x85, 0x84, 0x73, 0xe7, 0xfe,
+                0x72, 0x19, 0x72, 0xfb, 0x96, 0xe2, 0x15, 0xb8, 0x73, 0x77, 0xa1, 0x7c, 0xa3, 0x71,
+                0x0d, 0x93, 0xc9, 0xe9,
+            ],
         },
     ];
 
@@ -615,7 +678,7 @@ fn key_components() {
         }
 
         let pgk = ProofGenerationKey { ak, nsk };
-        let fvk = pgk.into_viewing_key(&JUBJUB);
+        let fvk = pgk.to_viewing_key(&JUBJUB);
         {
             let mut vec = Vec::new();
             fvk.nk.write(&mut vec).unwrap();
@@ -641,10 +704,10 @@ fn key_components() {
         let diversifier = Diversifier(tv.default_d);
         assert!(librustzcash_check_diversifier(&tv.default_d));
 
-        let addr = fvk.into_payment_address(diversifier, &JUBJUB).unwrap();
+        let addr = fvk.to_payment_address(diversifier, &JUBJUB).unwrap();
         {
             let mut vec = Vec::new();
-            addr.pk_d.write(&mut vec).unwrap();
+            addr.pk_d().write(&mut vec).unwrap();
             assert_eq!(&vec, &tv.default_pk_d);
         }
         {
@@ -662,5 +725,7 @@ fn key_components() {
             note.cm(&JUBJUB).into_repr().write_le(&mut vec).unwrap();
             assert_eq!(&vec, &tv.note_cm);
         }
+
+        assert_eq!(note.nf(&fvk, tv.note_pos, &JUBJUB), tv.note_nf);
     }
 }

librustzcash/src/tests/mmr.rs

@@ -0,0 +1,225 @@
+use zcash_history::{Entry, EntryLink, NodeData};
+
+use crate::{librustzcash_mmr_append, librustzcash_mmr_delete};
+
+const NODE_DATA_16L: &[u8] = include_bytes!("./res/tree16.dat");
+const NODE_DATA_1023L: &[u8] = include_bytes!("./res/tree1023.dat");
+
+struct TreeView {
+    peaks: Vec<(u32, Entry)>,
+    extra: Vec<(u32, Entry)>,
+}
+
+fn draft(into: &mut Vec<(u32, Entry)>, nodes: &[NodeData], peak_pos: usize, h: u32) {
+    let node_data = nodes[peak_pos - 1].clone();
+    let peak: Entry = match h {
+        0 => node_data.into(),
+        _ => Entry::new(
+            node_data,
+            EntryLink::Stored((peak_pos - (1 << h) - 1) as u32),
+            EntryLink::Stored((peak_pos - 2) as u32),
+        ),
+    };
+
+    into.push(((peak_pos - 1) as u32, peak));
+}
+
+fn prepare_tree(nodes: &[NodeData]) -> TreeView {
+    assert!(!nodes.is_empty());
+
+    // integer log2 of (nodes.len()+1), -1
+    let mut h = (32 - ((nodes.len() + 1) as u32).leading_zeros() - 1) - 1;
+    let mut peak_pos = (1 << (h + 1)) - 1;
+    let mut peaks = Vec::new();
+
+    // used later
+    let mut last_peak_pos = 0;
+    let mut last_peak_h = 0;
+
+    loop {
+        if peak_pos > nodes.len() {
+            // left child, -2^h
+            peak_pos -= 1 << h;
+            h -= 1;
+        }
+
+        if peak_pos <= nodes.len() {
+            draft(&mut peaks, nodes, peak_pos, h);
+
+            // save to be used in next loop
+            last_peak_pos = peak_pos;
+            last_peak_h = h;
+
+            // right sibling
+            peak_pos += (1 << (h + 1)) - 1;
+        }
+
+        if h == 0 {
+            break;
+        }
+    }
+
+    // for deletion, everything on the right slope of the last peak should be pre-loaded
+    let mut extra = Vec::new();
+    let mut h = last_peak_h;
+    let mut peak_pos = last_peak_pos;
+
+    while h > 0 {
+        let left_pos = peak_pos - (1 << h);
+        let right_pos = peak_pos - 1;
+        h -= 1;
+
+        // drafting left child
+        draft(&mut extra, nodes, left_pos, h);
+
+        // drafting right child
+        draft(&mut extra, nodes, right_pos, h);
+
+        // continuing on right slope
+        peak_pos = right_pos;
+    }
+
+    TreeView { peaks, extra }
+}
+
+fn preload_tree_append(nodes: &[NodeData]) -> (Vec<u32>, Vec<[u8; zcash_history::MAX_ENTRY_SIZE]>) {
+    assert!(!nodes.is_empty());
+
+    let tree_view = prepare_tree(nodes);
+
+    let mut indices = Vec::new();
+    let mut bytes = Vec::new();
+
+    for (idx, entry) in tree_view.peaks.into_iter() {
+        let mut buf = [0u8; zcash_history::MAX_ENTRY_SIZE];
+        entry
+            .write(&mut &mut buf[..])
+            .expect("Cannot fail if enough buffer length");
+        indices.push(idx);
+        bytes.push(buf);
+    }
+
+    (indices, bytes)
+}
+
+// also returns number of peaks
+fn preload_tree_delete(
+    nodes: &[NodeData],
+) -> (Vec<u32>, Vec<[u8; zcash_history::MAX_ENTRY_SIZE]>, usize) {
+    assert!(!nodes.is_empty());
+
+    let tree_view = prepare_tree(nodes);
+
+    let mut indices = Vec::new();
+    let mut bytes = Vec::new();
+
+    let peak_count = tree_view.peaks.len();
+
+    for (idx, entry) in tree_view
+        .peaks
+        .into_iter()
+        .chain(tree_view.extra.into_iter())
+    {
+        let mut buf = [0u8; zcash_history::MAX_ENTRY_SIZE];
+        entry
+            .write(&mut &mut buf[..])
+            .expect("Cannot fail if enough buffer length");
+        indices.push(idx);
+        bytes.push(buf);
+    }
+
+    (indices, bytes, peak_count)
+}
+
+fn load_nodes(bytes: &'static [u8]) -> Vec<NodeData> {
+    let mut res = Vec::new();
+    let mut cursor = std::io::Cursor::new(bytes);
+    while (cursor.position() as usize) < bytes.len() {
+        let node_data = zcash_history::NodeData::read(0, &mut cursor)
+            .expect("Statically checked to be correct");
+        res.push(node_data);
+    }
+
+    res
+}
+
+#[test]
+fn append() {
+    let nodes = load_nodes(NODE_DATA_16L);
+    let (indices, peaks) = preload_tree_append(&nodes);
+
+    let mut rt_ret = [0u8; 32];
+
+    let mut buf_ret = Vec::<[u8; zcash_history::MAX_NODE_DATA_SIZE]>::with_capacity(32);
+
+    let mut new_node_data = [0u8; zcash_history::MAX_NODE_DATA_SIZE];
+    let new_node = NodeData {
+        consensus_branch_id: 0,
+        subtree_commitment: [0u8; 32],
+        start_time: 101,
+        end_time: 110,
+        start_target: 190,
+        end_target: 200,
+        start_sapling_root: [0u8; 32],
+        end_sapling_root: [0u8; 32],
+        subtree_total_work: Default::default(),
+        start_height: 10,
+        end_height: 10,
+        sapling_tx: 13,
+    };
+    new_node
+        .write(&mut &mut new_node_data[..])
+        .expect("Failed to write node data");
+
+    let result = librustzcash_mmr_append(
+        0,
+        nodes.len() as u32,
+        indices.as_ptr(),
+        peaks.as_ptr(),
+        peaks.len(),
+        &new_node_data,
+        &mut rt_ret,
+        buf_ret.as_mut_ptr(),
+    );
+
+    unsafe {
+        buf_ret.set_len(result as usize);
+    }
+
+    assert_eq!(result, 2);
+
+    let new_node_1 =
+        NodeData::from_bytes(0, &buf_ret[0][..]).expect("Failed to reconstruct return node #1");
+
+    let new_node_2 =
+        NodeData::from_bytes(0, &buf_ret[1][..]).expect("Failed to reconstruct return node #2");
+
+    assert_eq!(new_node_1.start_height, 10);
+    assert_eq!(new_node_1.end_height, 10);
+
+    // this is combined new node (which is `new_node_1`) + the one which was there before (for block #9)
+    assert_eq!(new_node_2.start_height, 9);
+    assert_eq!(new_node_2.end_height, 10);
+    assert_eq!(new_node_2.sapling_tx, 27);
+}
+
+#[test]
+fn delete() {
+    let nodes = load_nodes(NODE_DATA_1023L);
+    let (indices, nodes, peak_count) = preload_tree_delete(&nodes);
+
+    let mut rt_ret = [0u8; 32];
+
+    let result = librustzcash_mmr_delete(
+        0,
+        nodes.len() as u32,
+        indices.as_ptr(),
+        nodes.as_ptr(),
+        peak_count,
+        indices.len() - peak_count,
+        &mut rt_ret,
+    );
+
+    // Deleting from full tree of 9 height would result in cascade deleting of 10 nodes
+    assert_eq!(result, 10);
+}

librustzcash/src/tests/mod.rs

@@ -1,9 +1,10 @@
-use sapling_crypto::jubjub::{FixedGenerators, JubjubParams};
+use zcash_primitives::jubjub::{FixedGenerators, JubjubParams};
 
 use super::JUBJUB;
 
 mod key_agreement;
 mod key_components;
+mod mmr;
 mod notes;
 mod signatures;
 

librustzcash/src/tests/notes.rs

@@ -1,5 +1,5 @@
-use librustzcash_sapling_compute_cm;
+use crate::librustzcash_sapling_compute_cm;
-use librustzcash_sapling_compute_nf;
+use crate::librustzcash_sapling_compute_nf;
 
 #[test]
 fn notes() {

librustzcash/src/tests/signatures.rs

@@ -1,8 +1,7 @@
-use pairing::{bls12_381::Bls12, PrimeField, PrimeFieldRepr};
+use ff::{PrimeField, PrimeFieldRepr};
-use sapling_crypto::{
+use pairing::bls12_381::Bls12;
-    jubjub::{FixedGenerators, JubjubEngine},
+use zcash_primitives::jubjub::{FixedGenerators, JubjubEngine};
-    redjubjub::{PrivateKey, PublicKey, Signature},
+use zcash_primitives::redjubjub::{PrivateKey, PublicKey, Signature};
-};
 
 use super::JUBJUB;
 

pairing/.gitignore

@@ -0,0 +1,3 @@
+target/
+**/*.rs.bk
+Cargo.lock

pairing/COPYRIGHT

@@ -0,0 +1,14 @@
+Copyrights in the "pairing" library are retained by their contributors. No
+copyright assignment is required to contribute to the "pairing" library.
+
+The "pairing" library is licensed under either of
+
+ * Apache License, Version 2.0, (see ./LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license (see ./LICENSE-MIT or http://opensource.org/licenses/MIT)
+
+at your option.
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

pairing/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "pairing"
+
+# Remember to change version string in README.md.
+version = "0.15.1"
+authors = [
+    "Sean Bowe <ewillbefull@gmail.com>",
+    "Jack Grigg <jack@z.cash>",
+]
+readme = "README.md"
+license = "MIT/Apache-2.0"
+
+description = "Pairing-friendly elliptic curve library"
+documentation = "https://docs.rs/pairing/"
+homepage = "https://github.com/ebfull/pairing"
+repository = "https://github.com/ebfull/pairing"
+edition ="2018"
+
+[dependencies]
+byteorder = "1"
+ff = { version = "^0.5.2", path = "../ff", features = ["derive"] }
+group = { version = "0.2.0", path = "../group" }
+rand_core = "0.5"
+
+[dev-dependencies]
+rand_xorshift = "0.2"
+
+[features]
+unstable-features = ["expose-arith"]
+expose-arith = []
+default = []
+
+[badges]
+maintenance = { status = "actively-developed" }

pairing/LICENSE-APACHE

@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
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+
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+
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+   Contributor provides its Contributions) on an "AS IS" BASIS,
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+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
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+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
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+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
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+   file or class name and description of purpose be included on the
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+
+Copyright [yyyy] [name of copyright owner]
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+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
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+
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+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

pairing/LICENSE-MIT

@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

pairing/README.md

@@ -0,0 +1,39 @@
+# pairing [![Crates.io](https://img.shields.io/crates/v/pairing.svg)](https://crates.io/crates/pairing) #
+
+`pairing` is a crate for using pairing-friendly elliptic curves.
+
+Currently, only the [BLS12-381](https://z.cash/blog/new-snark-curve.html)
+construction is implemented.
+
+## Roadmap
+
+`pairing` is being refactored into a generic library for working with
+pairing-friendly curves. After the refactor, `pairing` will provide basic traits
+for pairing-friendly elliptic curve constructions, while specific curves will be
+in separate crates.
+
+## [Documentation](https://docs.rs/pairing/)
+
+Bring the `pairing` crate into your project just as you normally would.
+
+## Security Warnings
+
+This library does not make any guarantees about constant-time operations, memory
+access patterns, or resistance to side-channel attacks.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.

pairing/benches/bls12_381/ec.rs

@@ -0,0 +1,149 @@
+mod g1 {
+    use rand_core::SeedableRng;
+    use rand_xorshift::XorShiftRng;
+
+    use ff::Field;
+    use group::CurveProjective;
+    use pairing::bls12_381::*;
+
+    #[bench]
+    fn bench_g1_mul_assign(b: &mut ::test::Bencher) {
+        const SAMPLES: usize = 1000;
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let v: Vec<(G1, Fr)> = (0..SAMPLES)
+            .map(|_| (G1::random(&mut rng), Fr::random(&mut rng)))
+            .collect();
+
+        let mut count = 0;
+        b.iter(|| {
+            let mut tmp = v[count].0;
+            tmp.mul_assign(v[count].1);
+            count = (count + 1) % SAMPLES;
+            tmp
+        });
+    }
+
+    #[bench]
+    fn bench_g1_add_assign(b: &mut ::test::Bencher) {
+        const SAMPLES: usize = 1000;
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let v: Vec<(G1, G1)> = (0..SAMPLES)
+            .map(|_| (G1::random(&mut rng), G1::random(&mut rng)))
+            .collect();
+
+        let mut count = 0;
+        b.iter(|| {
+            let mut tmp = v[count].0;
+            tmp.add_assign(&v[count].1);
+            count = (count + 1) % SAMPLES;
+            tmp
+        });
+    }
+
+    #[bench]
+    fn bench_g1_add_assign_mixed(b: &mut ::test::Bencher) {
+        const SAMPLES: usize = 1000;
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let v: Vec<(G1, G1Affine)> = (0..SAMPLES)
+            .map(|_| (G1::random(&mut rng), G1::random(&mut rng).into()))
+            .collect();
+
+        let mut count = 0;
+        b.iter(|| {
+            let mut tmp = v[count].0;
+            tmp.add_assign_mixed(&v[count].1);
+            count = (count + 1) % SAMPLES;
+            tmp
+        });
+    }
+}
+
+mod g2 {
+    use rand_core::SeedableRng;
+    use rand_xorshift::XorShiftRng;
+
+    use ff::Field;
+    use group::CurveProjective;
+    use pairing::bls12_381::*;
+
+    #[bench]
+    fn bench_g2_mul_assign(b: &mut ::test::Bencher) {
+        const SAMPLES: usize = 1000;
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let v: Vec<(G2, Fr)> = (0..SAMPLES)
+            .map(|_| (G2::random(&mut rng), Fr::random(&mut rng)))
+            .collect();
+
+        let mut count = 0;
+        b.iter(|| {
+            let mut tmp = v[count].0;
+            tmp.mul_assign(v[count].1);
+            count = (count + 1) % SAMPLES;
+            tmp
+        });
+    }
+
+    #[bench]
+    fn bench_g2_add_assign(b: &mut ::test::Bencher) {
+        const SAMPLES: usize = 1000;
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let v: Vec<(G2, G2)> = (0..SAMPLES)
+            .map(|_| (G2::random(&mut rng), G2::random(&mut rng)))
+            .collect();
+
+        let mut count = 0;
+        b.iter(|| {
+            let mut tmp = v[count].0;
+            tmp.add_assign(&v[count].1);
+            count = (count + 1) % SAMPLES;
+            tmp
+        });
+    }
+
+    #[bench]
+    fn bench_g2_add_assign_mixed(b: &mut ::test::Bencher) {
+        const SAMPLES: usize = 1000;
+
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        let v: Vec<(G2, G2Affine)> = (0..SAMPLES)
+            .map(|_| (G2::random(&mut rng), G2::random(&mut rng).into()))
+            .collect();
+
+        let mut count = 0;
+        b.iter(|| {
+            let mut tmp = v[count].0;
+            tmp.add_assign_mixed(&v[count].1);
+            count = (count + 1) % SAMPLES;
+            tmp
+        });
+    }
+}

pairing/benches/bls12_381/fq.rs

@@ -0,0 +1,317 @@
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use ff::{Field, PrimeField, PrimeFieldRepr, SqrtField};
+use pairing::bls12_381::*;
+
+#[bench]
+fn bench_fq_repr_add_nocarry(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(FqRepr, FqRepr)> = (0..SAMPLES)
+        .map(|_| {
+            let mut tmp1 = Fq::random(&mut rng).into_repr();
+            let mut tmp2 = Fq::random(&mut rng).into_repr();
+            // Shave a few bits off to avoid overflow.
+            for _ in 0..3 {
+                tmp1.div2();
+                tmp2.div2();
+            }
+            (tmp1, tmp2)
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.add_nocarry(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_repr_sub_noborrow(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(FqRepr, FqRepr)> = (0..SAMPLES)
+        .map(|_| {
+            let tmp1 = Fq::random(&mut rng).into_repr();
+            let mut tmp2 = tmp1;
+            // Ensure tmp2 is smaller than tmp1.
+            for _ in 0..10 {
+                tmp2.div2();
+            }
+            (tmp1, tmp2)
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.sub_noborrow(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_repr_num_bits(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FqRepr> = (0..SAMPLES)
+        .map(|_| Fq::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = v[count].num_bits();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_repr_mul2(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FqRepr> = (0..SAMPLES)
+        .map(|_| Fq::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.mul2();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_repr_div2(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FqRepr> = (0..SAMPLES)
+        .map(|_| Fq::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.div2();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_add_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq, Fq)> = (0..SAMPLES)
+        .map(|_| (Fq::random(&mut rng), Fq::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.add_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_sub_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq, Fq)> = (0..SAMPLES)
+        .map(|_| (Fq::random(&mut rng), Fq::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.sub_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_mul_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq, Fq)> = (0..SAMPLES)
+        .map(|_| (Fq::random(&mut rng), Fq::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.mul_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_square(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq> = (0..SAMPLES).map(|_| Fq::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.square();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_inverse(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq> = (0..SAMPLES).map(|_| Fq::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        v[count].inverse()
+    });
+}
+
+#[bench]
+fn bench_fq_negate(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq> = (0..SAMPLES).map(|_| Fq::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.negate();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq_sqrt(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq> = (0..SAMPLES)
+        .map(|_| {
+            let mut tmp = Fq::random(&mut rng);
+            tmp.square();
+            tmp
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        v[count].sqrt()
+    });
+}
+
+#[bench]
+fn bench_fq_into_repr(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq> = (0..SAMPLES).map(|_| Fq::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        v[count].into_repr()
+    });
+}
+
+#[bench]
+fn bench_fq_from_repr(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FqRepr> = (0..SAMPLES)
+        .map(|_| Fq::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        Fq::from_repr(v[count])
+    });
+}

pairing/benches/bls12_381/fq12.rs

@@ -0,0 +1,110 @@
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use ff::Field;
+use pairing::bls12_381::*;
+
+#[bench]
+fn bench_fq12_add_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq12, Fq12)> = (0..SAMPLES)
+        .map(|_| (Fq12::random(&mut rng), Fq12::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.add_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq12_sub_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq12, Fq12)> = (0..SAMPLES)
+        .map(|_| (Fq12::random(&mut rng), Fq12::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.sub_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq12_mul_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq12, Fq12)> = (0..SAMPLES)
+        .map(|_| (Fq12::random(&mut rng), Fq12::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.mul_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq12_squaring(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq12> = (0..SAMPLES).map(|_| Fq12::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.square();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq12_inverse(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq12> = (0..SAMPLES).map(|_| Fq12::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = v[count].inverse();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}

pairing/benches/bls12_381/fq2.rs

@@ -0,0 +1,129 @@
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use ff::{Field, SqrtField};
+use pairing::bls12_381::*;
+
+#[bench]
+fn bench_fq2_add_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq2, Fq2)> = (0..SAMPLES)
+        .map(|_| (Fq2::random(&mut rng), Fq2::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.add_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq2_sub_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq2, Fq2)> = (0..SAMPLES)
+        .map(|_| (Fq2::random(&mut rng), Fq2::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.sub_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq2_mul_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fq2, Fq2)> = (0..SAMPLES)
+        .map(|_| (Fq2::random(&mut rng), Fq2::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.mul_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq2_squaring(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq2> = (0..SAMPLES).map(|_| Fq2::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.square();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq2_inverse(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq2> = (0..SAMPLES).map(|_| Fq2::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = v[count].inverse();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fq2_sqrt(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq2> = (0..SAMPLES).map(|_| Fq2::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = v[count].sqrt();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}

pairing/benches/bls12_381/fr.rs

@@ -0,0 +1,317 @@
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use ff::{Field, PrimeField, PrimeFieldRepr, SqrtField};
+use pairing::bls12_381::*;
+
+#[bench]
+fn bench_fr_repr_add_nocarry(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(FrRepr, FrRepr)> = (0..SAMPLES)
+        .map(|_| {
+            let mut tmp1 = Fr::random(&mut rng).into_repr();
+            let mut tmp2 = Fr::random(&mut rng).into_repr();
+            // Shave a few bits off to avoid overflow.
+            for _ in 0..3 {
+                tmp1.div2();
+                tmp2.div2();
+            }
+            (tmp1, tmp2)
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.add_nocarry(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_repr_sub_noborrow(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(FrRepr, FrRepr)> = (0..SAMPLES)
+        .map(|_| {
+            let tmp1 = Fr::random(&mut rng).into_repr();
+            let mut tmp2 = tmp1;
+            // Ensure tmp2 is smaller than tmp1.
+            for _ in 0..10 {
+                tmp2.div2();
+            }
+            (tmp1, tmp2)
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.sub_noborrow(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_repr_num_bits(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FrRepr> = (0..SAMPLES)
+        .map(|_| Fr::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = v[count].num_bits();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_repr_mul2(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FrRepr> = (0..SAMPLES)
+        .map(|_| Fr::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.mul2();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_repr_div2(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FrRepr> = (0..SAMPLES)
+        .map(|_| Fr::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.div2();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_add_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fr, Fr)> = (0..SAMPLES)
+        .map(|_| (Fr::random(&mut rng), Fr::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.add_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_sub_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fr, Fr)> = (0..SAMPLES)
+        .map(|_| (Fr::random(&mut rng), Fr::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.sub_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_mul_assign(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(Fr, Fr)> = (0..SAMPLES)
+        .map(|_| (Fr::random(&mut rng), Fr::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count].0;
+        tmp.mul_assign(&v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_square(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fr> = (0..SAMPLES).map(|_| Fr::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.square();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_inverse(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fr> = (0..SAMPLES).map(|_| Fr::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        v[count].inverse()
+    });
+}
+
+#[bench]
+fn bench_fr_negate(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fr> = (0..SAMPLES).map(|_| Fr::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let mut tmp = v[count];
+        tmp.negate();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_fr_sqrt(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fr> = (0..SAMPLES)
+        .map(|_| {
+            let mut tmp = Fr::random(&mut rng);
+            tmp.square();
+            tmp
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        v[count].sqrt()
+    });
+}
+
+#[bench]
+fn bench_fr_into_repr(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fr> = (0..SAMPLES).map(|_| Fr::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        v[count].into_repr()
+    });
+}
+
+#[bench]
+fn bench_fr_from_repr(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<FrRepr> = (0..SAMPLES)
+        .map(|_| Fr::random(&mut rng).into_repr())
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        count = (count + 1) % SAMPLES;
+        Fr::from_repr(v[count])
+    });
+}

pairing/benches/bls12_381/mod.rs

@@ -0,0 +1,124 @@
+mod ec;
+mod fq;
+mod fq12;
+mod fq2;
+mod fr;
+
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use group::CurveProjective;
+use pairing::bls12_381::*;
+use pairing::{Engine, PairingCurveAffine};
+
+#[bench]
+fn bench_pairing_g1_preparation(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<G1> = (0..SAMPLES).map(|_| G1::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = G1Affine::from(v[count]).prepare();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_pairing_g2_preparation(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<G2> = (0..SAMPLES).map(|_| G2::random(&mut rng)).collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = G2Affine::from(v[count]).prepare();
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_pairing_miller_loop(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(G1Prepared, G2Prepared)> = (0..SAMPLES)
+        .map(|_| {
+            (
+                G1Affine::from(G1::random(&mut rng)).prepare(),
+                G2Affine::from(G2::random(&mut rng)).prepare(),
+            )
+        })
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = Bls12::miller_loop(&[(&v[count].0, &v[count].1)]);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_pairing_final_exponentiation(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<Fq12> = (0..SAMPLES)
+        .map(|_| {
+            (
+                G1Affine::from(G1::random(&mut rng)).prepare(),
+                G2Affine::from(G2::random(&mut rng)).prepare(),
+            )
+        })
+        .map(|(ref p, ref q)| Bls12::miller_loop(&[(p, q)]))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = Bls12::final_exponentiation(&v[count]);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}
+
+#[bench]
+fn bench_pairing_full(b: &mut ::test::Bencher) {
+    const SAMPLES: usize = 1000;
+
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let v: Vec<(G1, G2)> = (0..SAMPLES)
+        .map(|_| (G1::random(&mut rng), G2::random(&mut rng)))
+        .collect();
+
+    let mut count = 0;
+    b.iter(|| {
+        let tmp = Bls12::pairing(v[count].0, v[count].1);
+        count = (count + 1) % SAMPLES;
+        tmp
+    });
+}

pairing/benches/pairing_benches.rs

@@ -0,0 +1,10 @@
+#![feature(test)]
+
+extern crate ff;
+extern crate group;
+extern crate pairing;
+extern crate rand_core;
+extern crate rand_xorshift;
+extern crate test;
+
+mod bls12_381;

pairing/src/bls12_381/README.md

@@ -0,0 +1,71 @@
+# BLS12-381
+
+This is an implementation of the BLS12-381 pairing-friendly elliptic curve construction.
+
+## BLS12 Parameterization
+
+BLS12 curves are parameterized by a value *x* such that the base field modulus *q* and subgroup *r* can be computed by:
+
+* q = (x - 1)<sup>2</sup> ((x<sup>4</sup> - x<sup>2</sup> + 1) / 3) + x
+* r = (x<sup>4</sup> - x<sup>2</sup> + 1)
+
+Given primes *q* and *r* parameterized as above, we can easily construct an elliptic curve over the prime field F<sub>*q*</sub> which contains a subgroup of order *r* such that *r* | (*q*<sup>12</sup> - 1), giving it an embedding degree of 12. Instantiating its sextic twist over an extension field F<sub>q<sup>2</sup></sub> gives rise to an efficient bilinear pairing function between elements of the order *r* subgroups of either curves, into an order *r* multiplicative subgroup of F<sub>q<sup>12</sup></sub>.
+
+In zk-SNARK schemes, we require F<sub>r</sub> with large 2<sup>n</sup> roots of unity for performing efficient fast-fourier transforms. As such, guaranteeing that large 2<sup>n</sup> | (r - 1), or equivalently that *x* has a large 2<sup>n</sup> factor, gives rise to BLS12 curves suitable for zk-SNARKs.
+
+Due to recent research, it is estimated by many that *q* should be approximately 384 bits to target 128-bit security. Conveniently, *r* is approximately 256 bits when *q* is approximately 384 bits, making BLS12 curves ideal for 128-bit security. It also makes them ideal for many zk-SNARK applications, as the scalar field can be used for keying material such as embedded curve constructions.
+
+Many curves match our descriptions, but we require some extra properties for efficiency purposes:
+
+* *q* should be smaller than 2<sup>383</sup>, and *r* should be smaller than 2<sup>255</sup>, so that the most significant bit is unset when using 64-bit or 32-bit limbs. This allows for cheap reductions.
+* F<sub>q<sup>12</sup></sub> is typically constructed using towers of extension fields. As a byproduct of [research](https://eprint.iacr.org/2011/465.pdf) for BLS curves of embedding degree 24, we can identify subfamilies of BLS12 curves (for our purposes, where x mod 72 = {16, 64}) that produce efficient extension field towers and twisting isomorphisms.
+* We desire *x* of small Hamming weight, to increase the performance of the pairing function.
+
+## BLS12-381 Instantiation
+
+The BLS12-381 construction is instantiated by `x = -0xd201000000010000`, which produces the largest `q` and smallest Hamming weight of `x` that meets the above requirements. This produces:
+
+* q = `0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab` (381 bits)
+* r = `0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001` (255 bits)
+
+Our extension field tower is constructed as follows:
+
+1. F<sub>q<sup>2</sup></sub> is constructed as F<sub>q</sub>(u) / (u<sup>2</sup> - β) where β = -1.
+2. F<sub>q<sup>6</sup></sub> is constructed as F<sub>q<sup>2</sup></sub>(v) / (v<sup>3</sup> - ξ) where ξ = u + 1
+3. F<sub>q<sup>12</sup></sub> is constructed as F<sub>q<sup>6</sup></sub>(w) / (w<sup>2</sup> - γ) where γ = v
+
+Now, we instantiate the elliptic curve E(F<sub>q</sub>) : y<sup>2</sup> = x<sup>3</sup> + 4, and the elliptic curve E'(F<sub>q<sup>2</sup></sub>) : y<sup>2</sup> = x<sup>3</sup> + 4(u + 1).
+
+The group G<sub>1</sub> is the *r* order subgroup of E, which has cofactor (x - 1)<sup>2</sup> / 3. The group G<sub>2</sub> is the *r* order subgroup of E', which has cofactor (x<sup>8</sup> - 4x<sup>7</sup> + 5x<sup>6</sup> - 4x<sup>4</sup> + 6x<sup>3</sup> - 4x<sup>2</sup> - 4x + 13) / 9.
+
+### Generators
+
+The generators of G<sub>1</sub> and G<sub>2</sub> are computed by finding the lexicographically smallest valid `x`-coordinate, and its lexicographically smallest `y`-coordinate and scaling it by the cofactor such that the result is not the point at infinity.
+
+#### G1
+
+```
+x = 3685416753713387016781088315183077757961620795782546409894578378688607592378376318836054947676345821548104185464507
+y = 1339506544944476473020471379941921221584933875938349620426543736416511423956333506472724655353366534992391756441569
+```
+
+#### G2
+
+```
+x = 3059144344244213709971259814753781636986470325476647558659373206291635324768958432433509563104347017837885763365758*u + 352701069587466618187139116011060144890029952792775240219908644239793785735715026873347600343865175952761926303160
+y = 927553665492332455747201965776037880757740193453592970025027978793976877002675564980949289727957565575433344219582*u + 1985150602287291935568054521177171638300868978215655730859378665066344726373823718423869104263333984641494340347905
+```
+
+### Serialization
+
+* Fq elements are encoded in big-endian form. They occupy 48 bytes in this form.
+* Fq2 elements are encoded in big-endian form, meaning that the Fq element c0 + c1 * u is represented by the Fq element c1 followed by the Fq element c0. This means Fq2 elements occupy 96 bytes in this form.
+* The group G1 uses Fq elements for coordinates. The group G2 uses Fq2 elements for coordinates.
+* G1 and G2 elements can be encoded in uncompressed form (the x-coordinate followed by the y-coordinate) or in compressed form (just the x-coordinate). G1 elements occupy 96 bytes in uncompressed form, and 48 bytes in compressed form. G2 elements occupy 192 bytes in uncompressed form, and 96 bytes in compressed form.
+
+The most-significant three bits of a G1 or G2 encoding should be masked away before the coordinate(s) are interpreted. These bits are used to unambiguously represent the underlying element:
+
+* The most significant bit, when set, indicates that the point is in compressed form. Otherwise, the point is in uncompressed form.
+* The second-most significant bit indicates that the point is at infinity. If this bit is set, the remaining bits of the group element's encoding should be set to zero.
+* The third-most significant bit is set if (and only if) this point is in compressed form _and_ it is not the point at infinity _and_ its y-coordinate is the lexicographically largest of the two associated with the encoded x-coordinate.
+

pairing/src/bls12_381/fq12.rs

@@ -0,0 +1,192 @@
+use super::fq::FROBENIUS_COEFF_FQ12_C1;
+use super::fq2::Fq2;
+use super::fq6::Fq6;
+use ff::Field;
+use rand_core::RngCore;
+
+/// An element of Fq12, represented by c0 + c1 * w.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct Fq12 {
+    pub c0: Fq6,
+    pub c1: Fq6,
+}
+
+impl ::std::fmt::Display for Fq12 {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+        write!(f, "Fq12({} + {} * w)", self.c0, self.c1)
+    }
+}
+
+impl Fq12 {
+    pub fn conjugate(&mut self) {
+        self.c1.negate();
+    }
+
+    pub fn mul_by_014(&mut self, c0: &Fq2, c1: &Fq2, c4: &Fq2) {
+        let mut aa = self.c0;
+        aa.mul_by_01(c0, c1);
+        let mut bb = self.c1;
+        bb.mul_by_1(c4);
+        let mut o = *c1;
+        o.add_assign(c4);
+        self.c1.add_assign(&self.c0);
+        self.c1.mul_by_01(c0, &o);
+        self.c1.sub_assign(&aa);
+        self.c1.sub_assign(&bb);
+        self.c0 = bb;
+        self.c0.mul_by_nonresidue();
+        self.c0.add_assign(&aa);
+    }
+}
+
+impl Field for Fq12 {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+        Fq12 {
+            c0: Fq6::random(rng),
+            c1: Fq6::random(rng),
+        }
+    }
+
+    fn zero() -> Self {
+        Fq12 {
+            c0: Fq6::zero(),
+            c1: Fq6::zero(),
+        }
+    }
+
+    fn one() -> Self {
+        Fq12 {
+            c0: Fq6::one(),
+            c1: Fq6::zero(),
+        }
+    }
+
+    fn is_zero(&self) -> bool {
+        self.c0.is_zero() && self.c1.is_zero()
+    }
+
+    fn double(&mut self) {
+        self.c0.double();
+        self.c1.double();
+    }
+
+    fn negate(&mut self) {
+        self.c0.negate();
+        self.c1.negate();
+    }
+
+    fn add_assign(&mut self, other: &Self) {
+        self.c0.add_assign(&other.c0);
+        self.c1.add_assign(&other.c1);
+    }
+
+    fn sub_assign(&mut self, other: &Self) {
+        self.c0.sub_assign(&other.c0);
+        self.c1.sub_assign(&other.c1);
+    }
+
+    fn frobenius_map(&mut self, power: usize) {
+        self.c0.frobenius_map(power);
+        self.c1.frobenius_map(power);
+
+        self.c1.c0.mul_assign(&FROBENIUS_COEFF_FQ12_C1[power % 12]);
+        self.c1.c1.mul_assign(&FROBENIUS_COEFF_FQ12_C1[power % 12]);
+        self.c1.c2.mul_assign(&FROBENIUS_COEFF_FQ12_C1[power % 12]);
+    }
+
+    fn square(&mut self) {
+        let mut ab = self.c0;
+        ab.mul_assign(&self.c1);
+        let mut c0c1 = self.c0;
+        c0c1.add_assign(&self.c1);
+        let mut c0 = self.c1;
+        c0.mul_by_nonresidue();
+        c0.add_assign(&self.c0);
+        c0.mul_assign(&c0c1);
+        c0.sub_assign(&ab);
+        self.c1 = ab;
+        self.c1.add_assign(&ab);
+        ab.mul_by_nonresidue();
+        c0.sub_assign(&ab);
+        self.c0 = c0;
+    }
+
+    fn mul_assign(&mut self, other: &Self) {
+        let mut aa = self.c0;
+        aa.mul_assign(&other.c0);
+        let mut bb = self.c1;
+        bb.mul_assign(&other.c1);
+        let mut o = other.c0;
+        o.add_assign(&other.c1);
+        self.c1.add_assign(&self.c0);
+        self.c1.mul_assign(&o);
+        self.c1.sub_assign(&aa);
+        self.c1.sub_assign(&bb);
+        self.c0 = bb;
+        self.c0.mul_by_nonresidue();
+        self.c0.add_assign(&aa);
+    }
+
+    fn inverse(&self) -> Option<Self> {
+        let mut c0s = self.c0;
+        c0s.square();
+        let mut c1s = self.c1;
+        c1s.square();
+        c1s.mul_by_nonresidue();
+        c0s.sub_assign(&c1s);
+
+        c0s.inverse().map(|t| {
+            let mut tmp = Fq12 { c0: t, c1: t };
+            tmp.c0.mul_assign(&self.c0);
+            tmp.c1.mul_assign(&self.c1);
+            tmp.c1.negate();
+
+            tmp
+        })
+    }
+}
+
+#[cfg(test)]
+use rand_core::SeedableRng;
+#[cfg(test)]
+use rand_xorshift::XorShiftRng;
+
+#[test]
+fn test_fq12_mul_by_014() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let c0 = Fq2::random(&mut rng);
+        let c1 = Fq2::random(&mut rng);
+        let c5 = Fq2::random(&mut rng);
+        let mut a = Fq12::random(&mut rng);
+        let mut b = a;
+
+        a.mul_by_014(&c0, &c1, &c5);
+        b.mul_assign(&Fq12 {
+            c0: Fq6 {
+                c0,
+                c1,
+                c2: Fq2::zero(),
+            },
+            c1: Fq6 {
+                c0: Fq2::zero(),
+                c1: c5,
+                c2: Fq2::zero(),
+            },
+        });
+
+        assert_eq!(a, b);
+    }
+}
+
+#[test]
+fn fq12_field_tests() {
+    use ff::PrimeField;
+
+    crate::tests::field::random_field_tests::<Fq12>();
+    crate::tests::field::random_frobenius_tests::<Fq12, _>(super::fq::Fq::char(), 13);
+}

pairing/src/bls12_381/fq2.rs

@@ -0,0 +1,964 @@
+use super::fq::{Fq, FROBENIUS_COEFF_FQ2_C1, NEGATIVE_ONE};
+use ff::{Field, SqrtField};
+use rand_core::RngCore;
+
+use std::cmp::Ordering;
+
+/// An element of Fq2, represented by c0 + c1 * u.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct Fq2 {
+    pub c0: Fq,
+    pub c1: Fq,
+}
+
+impl ::std::fmt::Display for Fq2 {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+        write!(f, "Fq2({} + {} * u)", self.c0, self.c1)
+    }
+}
+
+/// `Fq2` elements are ordered lexicographically.
+impl Ord for Fq2 {
+    #[inline(always)]
+    fn cmp(&self, other: &Fq2) -> Ordering {
+        match self.c1.cmp(&other.c1) {
+            Ordering::Greater => Ordering::Greater,
+            Ordering::Less => Ordering::Less,
+            Ordering::Equal => self.c0.cmp(&other.c0),
+        }
+    }
+}
+
+impl PartialOrd for Fq2 {
+    #[inline(always)]
+    fn partial_cmp(&self, other: &Fq2) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Fq2 {
+    /// Multiply this element by the cubic and quadratic nonresidue 1 + u.
+    pub fn mul_by_nonresidue(&mut self) {
+        let t0 = self.c0;
+        self.c0.sub_assign(&self.c1);
+        self.c1.add_assign(&t0);
+    }
+
+    /// Norm of Fq2 as extension field in i over Fq
+    pub fn norm(&self) -> Fq {
+        let mut t0 = self.c0;
+        let mut t1 = self.c1;
+        t0.square();
+        t1.square();
+        t1.add_assign(&t0);
+
+        t1
+    }
+}
+
+impl Field for Fq2 {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+        Fq2 {
+            c0: Fq::random(rng),
+            c1: Fq::random(rng),
+        }
+    }
+
+    fn zero() -> Self {
+        Fq2 {
+            c0: Fq::zero(),
+            c1: Fq::zero(),
+        }
+    }
+
+    fn one() -> Self {
+        Fq2 {
+            c0: Fq::one(),
+            c1: Fq::zero(),
+        }
+    }
+
+    fn is_zero(&self) -> bool {
+        self.c0.is_zero() && self.c1.is_zero()
+    }
+
+    fn square(&mut self) {
+        let mut ab = self.c0;
+        ab.mul_assign(&self.c1);
+        let mut c0c1 = self.c0;
+        c0c1.add_assign(&self.c1);
+        let mut c0 = self.c1;
+        c0.negate();
+        c0.add_assign(&self.c0);
+        c0.mul_assign(&c0c1);
+        c0.sub_assign(&ab);
+        self.c1 = ab;
+        self.c1.add_assign(&ab);
+        c0.add_assign(&ab);
+        self.c0 = c0;
+    }
+
+    fn double(&mut self) {
+        self.c0.double();
+        self.c1.double();
+    }
+
+    fn negate(&mut self) {
+        self.c0.negate();
+        self.c1.negate();
+    }
+
+    fn add_assign(&mut self, other: &Self) {
+        self.c0.add_assign(&other.c0);
+        self.c1.add_assign(&other.c1);
+    }
+
+    fn sub_assign(&mut self, other: &Self) {
+        self.c0.sub_assign(&other.c0);
+        self.c1.sub_assign(&other.c1);
+    }
+
+    fn mul_assign(&mut self, other: &Self) {
+        let mut aa = self.c0;
+        aa.mul_assign(&other.c0);
+        let mut bb = self.c1;
+        bb.mul_assign(&other.c1);
+        let mut o = other.c0;
+        o.add_assign(&other.c1);
+        self.c1.add_assign(&self.c0);
+        self.c1.mul_assign(&o);
+        self.c1.sub_assign(&aa);
+        self.c1.sub_assign(&bb);
+        self.c0 = aa;
+        self.c0.sub_assign(&bb);
+    }
+
+    fn inverse(&self) -> Option<Self> {
+        let mut t1 = self.c1;
+        t1.square();
+        let mut t0 = self.c0;
+        t0.square();
+        t0.add_assign(&t1);
+        t0.inverse().map(|t| {
+            let mut tmp = Fq2 {
+                c0: self.c0,
+                c1: self.c1,
+            };
+            tmp.c0.mul_assign(&t);
+            tmp.c1.mul_assign(&t);
+            tmp.c1.negate();
+
+            tmp
+        })
+    }
+
+    fn frobenius_map(&mut self, power: usize) {
+        self.c1.mul_assign(&FROBENIUS_COEFF_FQ2_C1[power % 2]);
+    }
+}
+
+impl SqrtField for Fq2 {
+    fn legendre(&self) -> ::ff::LegendreSymbol {
+        self.norm().legendre()
+    }
+
+    fn sqrt(&self) -> Option<Self> {
+        // Algorithm 9, https://eprint.iacr.org/2012/685.pdf
+
+        if self.is_zero() {
+            Some(Self::zero())
+        } else {
+            // a1 = self^((q - 3) / 4)
+            let mut a1 = self.pow([
+                0xee7fbfffffffeaaa,
+                0x7aaffffac54ffff,
+                0xd9cc34a83dac3d89,
+                0xd91dd2e13ce144af,
+                0x92c6e9ed90d2eb35,
+                0x680447a8e5ff9a6,
+            ]);
+            let mut alpha = a1;
+            alpha.square();
+            alpha.mul_assign(self);
+            let mut a0 = alpha;
+            a0.frobenius_map(1);
+            a0.mul_assign(&alpha);
+
+            let neg1 = Fq2 {
+                c0: NEGATIVE_ONE,
+                c1: Fq::zero(),
+            };
+
+            if a0 == neg1 {
+                None
+            } else {
+                a1.mul_assign(self);
+
+                if alpha == neg1 {
+                    a1.mul_assign(&Fq2 {
+                        c0: Fq::zero(),
+                        c1: Fq::one(),
+                    });
+                } else {
+                    alpha.add_assign(&Fq2::one());
+                    // alpha = alpha^((q - 1) / 2)
+                    alpha = alpha.pow([
+                        0xdcff7fffffffd555,
+                        0xf55ffff58a9ffff,
+                        0xb39869507b587b12,
+                        0xb23ba5c279c2895f,
+                        0x258dd3db21a5d66b,
+                        0xd0088f51cbff34d,
+                    ]);
+                    a1.mul_assign(&alpha);
+                }
+
+                Some(a1)
+            }
+        }
+    }
+}
+
+#[test]
+fn test_fq2_ordering() {
+    let mut a = Fq2 {
+        c0: Fq::zero(),
+        c1: Fq::zero(),
+    };
+
+    let mut b = a.clone();
+
+    assert!(a.cmp(&b) == Ordering::Equal);
+    b.c0.add_assign(&Fq::one());
+    assert!(a.cmp(&b) == Ordering::Less);
+    a.c0.add_assign(&Fq::one());
+    assert!(a.cmp(&b) == Ordering::Equal);
+    b.c1.add_assign(&Fq::one());
+    assert!(a.cmp(&b) == Ordering::Less);
+    a.c0.add_assign(&Fq::one());
+    assert!(a.cmp(&b) == Ordering::Less);
+    a.c1.add_assign(&Fq::one());
+    assert!(a.cmp(&b) == Ordering::Greater);
+    b.c0.add_assign(&Fq::one());
+    assert!(a.cmp(&b) == Ordering::Equal);
+}
+
+#[test]
+fn test_fq2_basics() {
+    assert_eq!(
+        Fq2 {
+            c0: Fq::zero(),
+            c1: Fq::zero(),
+        },
+        Fq2::zero()
+    );
+    assert_eq!(
+        Fq2 {
+            c0: Fq::one(),
+            c1: Fq::zero(),
+        },
+        Fq2::one()
+    );
+    assert!(Fq2::zero().is_zero());
+    assert!(!Fq2::one().is_zero());
+    assert!(!Fq2 {
+        c0: Fq::zero(),
+        c1: Fq::one(),
+    }
+    .is_zero());
+}
+
+#[test]
+fn test_fq2_squaring() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::one(),
+        c1: Fq::one(),
+    }; // u + 1
+    a.square();
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::zero(),
+            c1: Fq::from_repr(FqRepr::from(2)).unwrap(),
+        }
+    ); // 2u
+
+    let mut a = Fq2 {
+        c0: Fq::zero(),
+        c1: Fq::one(),
+    }; // u
+    a.square();
+    assert_eq!(a, {
+        let mut neg1 = Fq::one();
+        neg1.negate();
+        Fq2 {
+            c0: neg1,
+            c1: Fq::zero(),
+        }
+    }); // -1
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x9c2c6309bbf8b598,
+            0x4eef5c946536f602,
+            0x90e34aab6fb6a6bd,
+            0xf7f295a94e58ae7c,
+            0x41b76dcc1c3fbe5e,
+            0x7080c5fa1d8e042,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x38f473b3c870a4ab,
+            0x6ad3291177c8c7e5,
+            0xdac5a4c911a4353e,
+            0xbfb99020604137a0,
+            0xfc58a7b7be815407,
+            0x10d1615e75250a21,
+        ]))
+        .unwrap(),
+    };
+    a.square();
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0xf262c28c538bcf68,
+                0xb9f2a66eae1073ba,
+                0xdc46ab8fad67ae0,
+                0xcb674157618da176,
+                0x4cf17b5893c3d327,
+                0x7eac81369c43361
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0xc1579cf58e980cf8,
+                0xa23eb7e12dd54d98,
+                0xe75138bce4cec7aa,
+                0x38d0d7275a9689e1,
+                0x739c983042779a65,
+                0x1542a61c8a8db994
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_mul() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x85c9f989e1461f03,
+            0xa2e33c333449a1d6,
+            0x41e461154a7354a3,
+            0x9ee53e7e84d7532e,
+            0x1c202d8ed97afb45,
+            0x51d3f9253e2516f,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0xa7348a8b511aedcf,
+            0x143c215d8176b319,
+            0x4cc48081c09b8903,
+            0x9533e4a9a5158be,
+            0x7a5e1ecb676d65f9,
+            0x180c3ee46656b008,
+        ]))
+        .unwrap(),
+    };
+    a.mul_assign(&Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0xe21f9169805f537e,
+            0xfc87e62e179c285d,
+            0x27ece175be07a531,
+            0xcd460f9f0c23e430,
+            0x6c9110292bfa409,
+            0x2c93a72eb8af83e,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x4b1c3f936d8992d4,
+            0x1d2a72916dba4c8a,
+            0x8871c508658d1e5f,
+            0x57a06d3135a752ae,
+            0x634cd3c6c565096d,
+            0x19e17334d4e93558,
+        ]))
+        .unwrap(),
+    });
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x95b5127e6360c7e4,
+                0xde29c31a19a6937e,
+                0xf61a96dacf5a39bc,
+                0x5511fe4d84ee5f78,
+                0x5310a202d92f9963,
+                0x1751afbe166e5399
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x84af0e1bd630117a,
+                0x6c63cd4da2c2aa7,
+                0x5ba6e5430e883d40,
+                0xc975106579c275ee,
+                0x33a9ac82ce4c5083,
+                0x1ef1a36c201589d
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_inverse() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    assert!(Fq2::zero().inverse().is_none());
+
+    let a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x85c9f989e1461f03,
+            0xa2e33c333449a1d6,
+            0x41e461154a7354a3,
+            0x9ee53e7e84d7532e,
+            0x1c202d8ed97afb45,
+            0x51d3f9253e2516f,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0xa7348a8b511aedcf,
+            0x143c215d8176b319,
+            0x4cc48081c09b8903,
+            0x9533e4a9a5158be,
+            0x7a5e1ecb676d65f9,
+            0x180c3ee46656b008,
+        ]))
+        .unwrap(),
+    };
+    let a = a.inverse().unwrap();
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x70300f9bcb9e594,
+                0xe5ecda5fdafddbb2,
+                0x64bef617d2915a8f,
+                0xdfba703293941c30,
+                0xa6c3d8f9586f2636,
+                0x1351ef01941b70c4
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x8c39fd76a8312cb4,
+                0x15d7b6b95defbff0,
+                0x947143f89faedee9,
+                0xcbf651a0f367afb2,
+                0xdf4e54f0d3ef15a6,
+                0x103bdf241afb0019
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_addition() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x2d0078036923ffc7,
+            0x11e59ea221a3b6d2,
+            0x8b1a52e0a90f59ed,
+            0xb966ce3bc2108b13,
+            0xccc649c4b9532bf3,
+            0xf8d295b2ded9dc,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x977df6efcdaee0db,
+            0x946ae52d684fa7ed,
+            0xbe203411c66fb3a5,
+            0xb3f8afc0ee248cad,
+            0x4e464dea5bcfd41e,
+            0x12d1137b8a6a837,
+        ]))
+        .unwrap(),
+    };
+    a.add_assign(&Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x619a02d78dc70ef2,
+            0xb93adfc9119e33e8,
+            0x4bf0b99a9f0dca12,
+            0x3b88899a42a6318f,
+            0x986a4a62fa82a49d,
+            0x13ce433fa26027f5,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x66323bf80b58b9b9,
+            0xa1379b6facf6e596,
+            0x402aef1fb797e32f,
+            0x2236f55246d0d44d,
+            0x4c8c1800eb104566,
+            0x11d6e20e986c2085,
+        ]))
+        .unwrap(),
+    });
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x8e9a7adaf6eb0eb9,
+                0xcb207e6b3341eaba,
+                0xd70b0c7b481d23ff,
+                0xf4ef57d604b6bca2,
+                0x65309427b3d5d090,
+                0x14c715d5553f01d2
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0xfdb032e7d9079a94,
+                0x35a2809d15468d83,
+                0xfe4b23317e0796d5,
+                0xd62fa51334f560fa,
+                0x9ad265eb46e01984,
+                0x1303f3465112c8bc
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_subtraction() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x2d0078036923ffc7,
+            0x11e59ea221a3b6d2,
+            0x8b1a52e0a90f59ed,
+            0xb966ce3bc2108b13,
+            0xccc649c4b9532bf3,
+            0xf8d295b2ded9dc,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x977df6efcdaee0db,
+            0x946ae52d684fa7ed,
+            0xbe203411c66fb3a5,
+            0xb3f8afc0ee248cad,
+            0x4e464dea5bcfd41e,
+            0x12d1137b8a6a837,
+        ]))
+        .unwrap(),
+    };
+    a.sub_assign(&Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x619a02d78dc70ef2,
+            0xb93adfc9119e33e8,
+            0x4bf0b99a9f0dca12,
+            0x3b88899a42a6318f,
+            0x986a4a62fa82a49d,
+            0x13ce433fa26027f5,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x66323bf80b58b9b9,
+            0xa1379b6facf6e596,
+            0x402aef1fb797e32f,
+            0x2236f55246d0d44d,
+            0x4c8c1800eb104566,
+            0x11d6e20e986c2085,
+        ]))
+        .unwrap(),
+    });
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x8565752bdb5c9b80,
+                0x7756bed7c15982e9,
+                0xa65a6be700b285fe,
+                0xe255902672ef6c43,
+                0x7f77a718021c342d,
+                0x72ba14049fe9881
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0xeb4abaf7c255d1cd,
+                0x11df49bc6cacc256,
+                0xe52617930588c69a,
+                0xf63905f39ad8cb1f,
+                0x4cd5dd9fb40b3b8f,
+                0x957411359ba6e4c
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_negation() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x2d0078036923ffc7,
+            0x11e59ea221a3b6d2,
+            0x8b1a52e0a90f59ed,
+            0xb966ce3bc2108b13,
+            0xccc649c4b9532bf3,
+            0xf8d295b2ded9dc,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x977df6efcdaee0db,
+            0x946ae52d684fa7ed,
+            0xbe203411c66fb3a5,
+            0xb3f8afc0ee248cad,
+            0x4e464dea5bcfd41e,
+            0x12d1137b8a6a837,
+        ]))
+        .unwrap(),
+    };
+    a.negate();
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x8cfe87fc96dbaae4,
+                0xcc6615c8fb0492d,
+                0xdc167fc04da19c37,
+                0xab107d49317487ab,
+                0x7e555df189f880e3,
+                0x19083f5486a10cbd
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x228109103250c9d0,
+                0x8a411ad149045812,
+                0xa9109e8f3041427e,
+                0xb07e9bc405608611,
+                0xfcd559cbe77bd8b8,
+                0x18d400b280d93e62
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_doubling() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x2d0078036923ffc7,
+            0x11e59ea221a3b6d2,
+            0x8b1a52e0a90f59ed,
+            0xb966ce3bc2108b13,
+            0xccc649c4b9532bf3,
+            0xf8d295b2ded9dc,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x977df6efcdaee0db,
+            0x946ae52d684fa7ed,
+            0xbe203411c66fb3a5,
+            0xb3f8afc0ee248cad,
+            0x4e464dea5bcfd41e,
+            0x12d1137b8a6a837,
+        ]))
+        .unwrap(),
+    };
+    a.double();
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x5a00f006d247ff8e,
+                0x23cb3d4443476da4,
+                0x1634a5c1521eb3da,
+                0x72cd9c7784211627,
+                0x998c938972a657e7,
+                0x1f1a52b65bdb3b9
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x2efbeddf9b5dc1b6,
+                0x28d5ca5ad09f4fdb,
+                0x7c4068238cdf674b,
+                0x67f15f81dc49195b,
+                0x9c8c9bd4b79fa83d,
+                0x25a226f714d506e
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_frobenius_map() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    let mut a = Fq2 {
+        c0: Fq::from_repr(FqRepr([
+            0x2d0078036923ffc7,
+            0x11e59ea221a3b6d2,
+            0x8b1a52e0a90f59ed,
+            0xb966ce3bc2108b13,
+            0xccc649c4b9532bf3,
+            0xf8d295b2ded9dc,
+        ]))
+        .unwrap(),
+        c1: Fq::from_repr(FqRepr([
+            0x977df6efcdaee0db,
+            0x946ae52d684fa7ed,
+            0xbe203411c66fb3a5,
+            0xb3f8afc0ee248cad,
+            0x4e464dea5bcfd41e,
+            0x12d1137b8a6a837,
+        ]))
+        .unwrap(),
+    };
+    a.frobenius_map(0);
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x2d0078036923ffc7,
+                0x11e59ea221a3b6d2,
+                0x8b1a52e0a90f59ed,
+                0xb966ce3bc2108b13,
+                0xccc649c4b9532bf3,
+                0xf8d295b2ded9dc
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x977df6efcdaee0db,
+                0x946ae52d684fa7ed,
+                0xbe203411c66fb3a5,
+                0xb3f8afc0ee248cad,
+                0x4e464dea5bcfd41e,
+                0x12d1137b8a6a837
+            ]))
+            .unwrap(),
+        }
+    );
+    a.frobenius_map(1);
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x2d0078036923ffc7,
+                0x11e59ea221a3b6d2,
+                0x8b1a52e0a90f59ed,
+                0xb966ce3bc2108b13,
+                0xccc649c4b9532bf3,
+                0xf8d295b2ded9dc
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x228109103250c9d0,
+                0x8a411ad149045812,
+                0xa9109e8f3041427e,
+                0xb07e9bc405608611,
+                0xfcd559cbe77bd8b8,
+                0x18d400b280d93e62
+            ]))
+            .unwrap(),
+        }
+    );
+    a.frobenius_map(1);
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x2d0078036923ffc7,
+                0x11e59ea221a3b6d2,
+                0x8b1a52e0a90f59ed,
+                0xb966ce3bc2108b13,
+                0xccc649c4b9532bf3,
+                0xf8d295b2ded9dc
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x977df6efcdaee0db,
+                0x946ae52d684fa7ed,
+                0xbe203411c66fb3a5,
+                0xb3f8afc0ee248cad,
+                0x4e464dea5bcfd41e,
+                0x12d1137b8a6a837
+            ]))
+            .unwrap(),
+        }
+    );
+    a.frobenius_map(2);
+    assert_eq!(
+        a,
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x2d0078036923ffc7,
+                0x11e59ea221a3b6d2,
+                0x8b1a52e0a90f59ed,
+                0xb966ce3bc2108b13,
+                0xccc649c4b9532bf3,
+                0xf8d295b2ded9dc
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0x977df6efcdaee0db,
+                0x946ae52d684fa7ed,
+                0xbe203411c66fb3a5,
+                0xb3f8afc0ee248cad,
+                0x4e464dea5bcfd41e,
+                0x12d1137b8a6a837
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_sqrt() {
+    use super::fq::FqRepr;
+    use ff::PrimeField;
+
+    assert_eq!(
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x476b4c309720e227,
+                0x34c2d04faffdab6,
+                0xa57e6fc1bab51fd9,
+                0xdb4a116b5bf74aa1,
+                0x1e58b2159dfe10e2,
+                0x7ca7da1f13606ac
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0xfa8de88b7516d2c3,
+                0x371a75ed14f41629,
+                0x4cec2dca577a3eb6,
+                0x212611bca4e99121,
+                0x8ee5394d77afb3d,
+                0xec92336650e49d5
+            ]))
+            .unwrap(),
+        }
+        .sqrt()
+        .unwrap(),
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0x40b299b2704258c5,
+                0x6ef7de92e8c68b63,
+                0x6d2ddbe552203e82,
+                0x8d7f1f723d02c1d3,
+                0x881b3e01b611c070,
+                0x10f6963bbad2ebc5
+            ]))
+            .unwrap(),
+            c1: Fq::from_repr(FqRepr([
+                0xc099534fc209e752,
+                0x7670594665676447,
+                0x28a20faed211efe7,
+                0x6b852aeaf2afcb1b,
+                0xa4c93b08105d71a9,
+                0x8d7cfff94216330
+            ]))
+            .unwrap(),
+        }
+    );
+
+    assert_eq!(
+        Fq2 {
+            c0: Fq::from_repr(FqRepr([
+                0xb9f78429d1517a6b,
+                0x1eabfffeb153ffff,
+                0x6730d2a0f6b0f624,
+                0x64774b84f38512bf,
+                0x4b1ba7b6434bacd7,
+                0x1a0111ea397fe69a
+            ]))
+            .unwrap(),
+            c1: Fq::zero(),
+        }
+        .sqrt()
+        .unwrap(),
+        Fq2 {
+            c0: Fq::zero(),
+            c1: Fq::from_repr(FqRepr([
+                0xb9fefffffd4357a3,
+                0x1eabfffeb153ffff,
+                0x6730d2a0f6b0f624,
+                0x64774b84f38512bf,
+                0x4b1ba7b6434bacd7,
+                0x1a0111ea397fe69a
+            ]))
+            .unwrap(),
+        }
+    );
+}
+
+#[test]
+fn test_fq2_legendre() {
+    use ff::LegendreSymbol::*;
+
+    assert_eq!(Zero, Fq2::zero().legendre());
+    // i^2 = -1
+    let mut m1 = Fq2::one();
+    m1.negate();
+    assert_eq!(QuadraticResidue, m1.legendre());
+    m1.mul_by_nonresidue();
+    assert_eq!(QuadraticNonResidue, m1.legendre());
+}
+
+#[cfg(test)]
+use rand_core::SeedableRng;
+#[cfg(test)]
+use rand_xorshift::XorShiftRng;
+
+#[test]
+fn test_fq2_mul_nonresidue() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let nqr = Fq2 {
+        c0: Fq::one(),
+        c1: Fq::one(),
+    };
+
+    for _ in 0..1000 {
+        let mut a = Fq2::random(&mut rng);
+        let mut b = a;
+        a.mul_by_nonresidue();
+        b.mul_assign(&nqr);
+
+        assert_eq!(a, b);
+    }
+}
+
+#[test]
+fn fq2_field_tests() {
+    use ff::PrimeField;
+
+    crate::tests::field::random_field_tests::<Fq2>();
+    crate::tests::field::random_sqrt_tests::<Fq2>();
+    crate::tests::field::random_frobenius_tests::<Fq2, _>(super::fq::Fq::char(), 13);
+}

pairing/src/bls12_381/fq6.rs

@@ -0,0 +1,383 @@
+use super::fq::{FROBENIUS_COEFF_FQ6_C1, FROBENIUS_COEFF_FQ6_C2};
+use super::fq2::Fq2;
+use ff::Field;
+use rand_core::RngCore;
+
+/// An element of Fq6, represented by c0 + c1 * v + c2 * v^(2).
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct Fq6 {
+    pub c0: Fq2,
+    pub c1: Fq2,
+    pub c2: Fq2,
+}
+
+impl ::std::fmt::Display for Fq6 {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+        write!(f, "Fq6({} + {} * v, {} * v^2)", self.c0, self.c1, self.c2)
+    }
+}
+
+impl Fq6 {
+    /// Multiply by quadratic nonresidue v.
+    pub fn mul_by_nonresidue(&mut self) {
+        use std::mem::swap;
+        swap(&mut self.c0, &mut self.c1);
+        swap(&mut self.c0, &mut self.c2);
+
+        self.c0.mul_by_nonresidue();
+    }
+
+    pub fn mul_by_1(&mut self, c1: &Fq2) {
+        let mut b_b = self.c1;
+        b_b.mul_assign(c1);
+
+        let mut t1 = *c1;
+        {
+            let mut tmp = self.c1;
+            tmp.add_assign(&self.c2);
+
+            t1.mul_assign(&tmp);
+            t1.sub_assign(&b_b);
+            t1.mul_by_nonresidue();
+        }
+
+        let mut t2 = *c1;
+        {
+            let mut tmp = self.c0;
+            tmp.add_assign(&self.c1);
+
+            t2.mul_assign(&tmp);
+            t2.sub_assign(&b_b);
+        }
+
+        self.c0 = t1;
+        self.c1 = t2;
+        self.c2 = b_b;
+    }
+
+    pub fn mul_by_01(&mut self, c0: &Fq2, c1: &Fq2) {
+        let mut a_a = self.c0;
+        let mut b_b = self.c1;
+        a_a.mul_assign(c0);
+        b_b.mul_assign(c1);
+
+        let mut t1 = *c1;
+        {
+            let mut tmp = self.c1;
+            tmp.add_assign(&self.c2);
+
+            t1.mul_assign(&tmp);
+            t1.sub_assign(&b_b);
+            t1.mul_by_nonresidue();
+            t1.add_assign(&a_a);
+        }
+
+        let mut t3 = *c0;
+        {
+            let mut tmp = self.c0;
+            tmp.add_assign(&self.c2);
+
+            t3.mul_assign(&tmp);
+            t3.sub_assign(&a_a);
+            t3.add_assign(&b_b);
+        }
+
+        let mut t2 = *c0;
+        t2.add_assign(c1);
+        {
+            let mut tmp = self.c0;
+            tmp.add_assign(&self.c1);
+
+            t2.mul_assign(&tmp);
+            t2.sub_assign(&a_a);
+            t2.sub_assign(&b_b);
+        }
+
+        self.c0 = t1;
+        self.c1 = t2;
+        self.c2 = t3;
+    }
+}
+
+impl Field for Fq6 {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+        Fq6 {
+            c0: Fq2::random(rng),
+            c1: Fq2::random(rng),
+            c2: Fq2::random(rng),
+        }
+    }
+
+    fn zero() -> Self {
+        Fq6 {
+            c0: Fq2::zero(),
+            c1: Fq2::zero(),
+            c2: Fq2::zero(),
+        }
+    }
+
+    fn one() -> Self {
+        Fq6 {
+            c0: Fq2::one(),
+            c1: Fq2::zero(),
+            c2: Fq2::zero(),
+        }
+    }
+
+    fn is_zero(&self) -> bool {
+        self.c0.is_zero() && self.c1.is_zero() && self.c2.is_zero()
+    }
+
+    fn double(&mut self) {
+        self.c0.double();
+        self.c1.double();
+        self.c2.double();
+    }
+
+    fn negate(&mut self) {
+        self.c0.negate();
+        self.c1.negate();
+        self.c2.negate();
+    }
+
+    fn add_assign(&mut self, other: &Self) {
+        self.c0.add_assign(&other.c0);
+        self.c1.add_assign(&other.c1);
+        self.c2.add_assign(&other.c2);
+    }
+
+    fn sub_assign(&mut self, other: &Self) {
+        self.c0.sub_assign(&other.c0);
+        self.c1.sub_assign(&other.c1);
+        self.c2.sub_assign(&other.c2);
+    }
+
+    fn frobenius_map(&mut self, power: usize) {
+        self.c0.frobenius_map(power);
+        self.c1.frobenius_map(power);
+        self.c2.frobenius_map(power);
+
+        self.c1.mul_assign(&FROBENIUS_COEFF_FQ6_C1[power % 6]);
+        self.c2.mul_assign(&FROBENIUS_COEFF_FQ6_C2[power % 6]);
+    }
+
+    fn square(&mut self) {
+        let mut s0 = self.c0;
+        s0.square();
+        let mut ab = self.c0;
+        ab.mul_assign(&self.c1);
+        let mut s1 = ab;
+        s1.double();
+        let mut s2 = self.c0;
+        s2.sub_assign(&self.c1);
+        s2.add_assign(&self.c2);
+        s2.square();
+        let mut bc = self.c1;
+        bc.mul_assign(&self.c2);
+        let mut s3 = bc;
+        s3.double();
+        let mut s4 = self.c2;
+        s4.square();
+
+        self.c0 = s3;
+        self.c0.mul_by_nonresidue();
+        self.c0.add_assign(&s0);
+
+        self.c1 = s4;
+        self.c1.mul_by_nonresidue();
+        self.c1.add_assign(&s1);
+
+        self.c2 = s1;
+        self.c2.add_assign(&s2);
+        self.c2.add_assign(&s3);
+        self.c2.sub_assign(&s0);
+        self.c2.sub_assign(&s4);
+    }
+
+    fn mul_assign(&mut self, other: &Self) {
+        let mut a_a = self.c0;
+        let mut b_b = self.c1;
+        let mut c_c = self.c2;
+        a_a.mul_assign(&other.c0);
+        b_b.mul_assign(&other.c1);
+        c_c.mul_assign(&other.c2);
+
+        let mut t1 = other.c1;
+        t1.add_assign(&other.c2);
+        {
+            let mut tmp = self.c1;
+            tmp.add_assign(&self.c2);
+
+            t1.mul_assign(&tmp);
+            t1.sub_assign(&b_b);
+            t1.sub_assign(&c_c);
+            t1.mul_by_nonresidue();
+            t1.add_assign(&a_a);
+        }
+
+        let mut t3 = other.c0;
+        t3.add_assign(&other.c2);
+        {
+            let mut tmp = self.c0;
+            tmp.add_assign(&self.c2);
+
+            t3.mul_assign(&tmp);
+            t3.sub_assign(&a_a);
+            t3.add_assign(&b_b);
+            t3.sub_assign(&c_c);
+        }
+
+        let mut t2 = other.c0;
+        t2.add_assign(&other.c1);
+        {
+            let mut tmp = self.c0;
+            tmp.add_assign(&self.c1);
+
+            t2.mul_assign(&tmp);
+            t2.sub_assign(&a_a);
+            t2.sub_assign(&b_b);
+            c_c.mul_by_nonresidue();
+            t2.add_assign(&c_c);
+        }
+
+        self.c0 = t1;
+        self.c1 = t2;
+        self.c2 = t3;
+    }
+
+    fn inverse(&self) -> Option<Self> {
+        let mut c0 = self.c2;
+        c0.mul_by_nonresidue();
+        c0.mul_assign(&self.c1);
+        c0.negate();
+        {
+            let mut c0s = self.c0;
+            c0s.square();
+            c0.add_assign(&c0s);
+        }
+        let mut c1 = self.c2;
+        c1.square();
+        c1.mul_by_nonresidue();
+        {
+            let mut c01 = self.c0;
+            c01.mul_assign(&self.c1);
+            c1.sub_assign(&c01);
+        }
+        let mut c2 = self.c1;
+        c2.square();
+        {
+            let mut c02 = self.c0;
+            c02.mul_assign(&self.c2);
+            c2.sub_assign(&c02);
+        }
+
+        let mut tmp1 = self.c2;
+        tmp1.mul_assign(&c1);
+        let mut tmp2 = self.c1;
+        tmp2.mul_assign(&c2);
+        tmp1.add_assign(&tmp2);
+        tmp1.mul_by_nonresidue();
+        tmp2 = self.c0;
+        tmp2.mul_assign(&c0);
+        tmp1.add_assign(&tmp2);
+
+        match tmp1.inverse() {
+            Some(t) => {
+                let mut tmp = Fq6 {
+                    c0: t,
+                    c1: t,
+                    c2: t,
+                };
+                tmp.c0.mul_assign(&c0);
+                tmp.c1.mul_assign(&c1);
+                tmp.c2.mul_assign(&c2);
+
+                Some(tmp)
+            }
+            None => None,
+        }
+    }
+}
+
+#[cfg(test)]
+use rand_core::SeedableRng;
+#[cfg(test)]
+use rand_xorshift::XorShiftRng;
+
+#[test]
+fn test_fq6_mul_nonresidue() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    let nqr = Fq6 {
+        c0: Fq2::zero(),
+        c1: Fq2::one(),
+        c2: Fq2::zero(),
+    };
+
+    for _ in 0..1000 {
+        let mut a = Fq6::random(&mut rng);
+        let mut b = a;
+        a.mul_by_nonresidue();
+        b.mul_assign(&nqr);
+
+        assert_eq!(a, b);
+    }
+}
+
+#[test]
+fn test_fq6_mul_by_1() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let c1 = Fq2::random(&mut rng);
+        let mut a = Fq6::random(&mut rng);
+        let mut b = a;
+
+        a.mul_by_1(&c1);
+        b.mul_assign(&Fq6 {
+            c0: Fq2::zero(),
+            c1,
+            c2: Fq2::zero(),
+        });
+
+        assert_eq!(a, b);
+    }
+}
+
+#[test]
+fn test_fq6_mul_by_01() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let c0 = Fq2::random(&mut rng);
+        let c1 = Fq2::random(&mut rng);
+        let mut a = Fq6::random(&mut rng);
+        let mut b = a;
+
+        a.mul_by_01(&c0, &c1);
+        b.mul_assign(&Fq6 {
+            c0,
+            c1,
+            c2: Fq2::zero(),
+        });
+
+        assert_eq!(a, b);
+    }
+}
+
+#[test]
+fn fq6_field_tests() {
+    use ff::PrimeField;
+
+    crate::tests::field::random_field_tests::<Fq6>();
+    crate::tests::field::random_frobenius_tests::<Fq6, _>(super::fq::Fq::char(), 13);
+}

pairing/src/bls12_381/mod.rs

@@ -0,0 +1,373 @@
+//! An implementation of the BLS12-381 pairing-friendly elliptic curve
+//! construction.
+
+mod ec;
+mod fq;
+mod fq12;
+mod fq2;
+mod fq6;
+mod fr;
+
+#[cfg(test)]
+mod tests;
+
+pub use self::ec::{
+    G1Affine, G1Compressed, G1Prepared, G1Uncompressed, G2Affine, G2Compressed, G2Prepared,
+    G2Uncompressed, G1, G2,
+};
+pub use self::fq::{Fq, FqRepr};
+pub use self::fq12::Fq12;
+pub use self::fq2::Fq2;
+pub use self::fq6::Fq6;
+pub use self::fr::{Fr, FrRepr};
+
+use super::{Engine, PairingCurveAffine};
+
+use ff::{BitIterator, Field, ScalarEngine};
+use group::CurveAffine;
+
+// The BLS parameter x for BLS12-381 is -0xd201000000010000
+const BLS_X: u64 = 0xd201000000010000;
+const BLS_X_IS_NEGATIVE: bool = true;
+
+#[derive(Clone, Debug)]
+pub struct Bls12;
+
+impl ScalarEngine for Bls12 {
+    type Fr = Fr;
+}
+
+impl Engine for Bls12 {
+    type G1 = G1;
+    type G1Affine = G1Affine;
+    type G2 = G2;
+    type G2Affine = G2Affine;
+    type Fq = Fq;
+    type Fqe = Fq2;
+    type Fqk = Fq12;
+
+    fn miller_loop<'a, I>(i: I) -> Self::Fqk
+    where
+        I: IntoIterator<
+            Item = &'a (
+                &'a <Self::G1Affine as PairingCurveAffine>::Prepared,
+                &'a <Self::G2Affine as PairingCurveAffine>::Prepared,
+            ),
+        >,
+    {
+        let mut pairs = vec![];
+        for &(p, q) in i {
+            if !p.is_zero() && !q.is_zero() {
+                pairs.push((p, q.coeffs.iter()));
+            }
+        }
+
+        // Twisting isomorphism from E to E'
+        fn ell(f: &mut Fq12, coeffs: &(Fq2, Fq2, Fq2), p: &G1Affine) {
+            let mut c0 = coeffs.0;
+            let mut c1 = coeffs.1;
+
+            c0.c0.mul_assign(&p.y);
+            c0.c1.mul_assign(&p.y);
+
+            c1.c0.mul_assign(&p.x);
+            c1.c1.mul_assign(&p.x);
+
+            // Sparse multiplication in Fq12
+            f.mul_by_014(&coeffs.2, &c1, &c0);
+        }
+
+        let mut f = Fq12::one();
+
+        let mut found_one = false;
+        for i in BitIterator::new(&[BLS_X >> 1]) {
+            if !found_one {
+                found_one = i;
+                continue;
+            }
+
+            for &mut (p, ref mut coeffs) in &mut pairs {
+                ell(&mut f, coeffs.next().unwrap(), &p.0);
+            }
+
+            if i {
+                for &mut (p, ref mut coeffs) in &mut pairs {
+                    ell(&mut f, coeffs.next().unwrap(), &p.0);
+                }
+            }
+
+            f.square();
+        }
+
+        for &mut (p, ref mut coeffs) in &mut pairs {
+            ell(&mut f, coeffs.next().unwrap(), &p.0);
+        }
+
+        if BLS_X_IS_NEGATIVE {
+            f.conjugate();
+        }
+
+        f
+    }
+
+    fn final_exponentiation(r: &Fq12) -> Option<Fq12> {
+        let mut f1 = *r;
+        f1.conjugate();
+
+        match r.inverse() {
+            Some(mut f2) => {
+                let mut r = f1;
+                r.mul_assign(&f2);
+                f2 = r;
+                r.frobenius_map(2);
+                r.mul_assign(&f2);
+
+                fn exp_by_x(f: &mut Fq12, x: u64) {
+                    *f = f.pow(&[x]);
+                    if BLS_X_IS_NEGATIVE {
+                        f.conjugate();
+                    }
+                }
+
+                let mut x = BLS_X;
+                let mut y0 = r;
+                y0.square();
+                let mut y1 = y0;
+                exp_by_x(&mut y1, x);
+                x >>= 1;
+                let mut y2 = y1;
+                exp_by_x(&mut y2, x);
+                x <<= 1;
+                let mut y3 = r;
+                y3.conjugate();
+                y1.mul_assign(&y3);
+                y1.conjugate();
+                y1.mul_assign(&y2);
+                y2 = y1;
+                exp_by_x(&mut y2, x);
+                y3 = y2;
+                exp_by_x(&mut y3, x);
+                y1.conjugate();
+                y3.mul_assign(&y1);
+                y1.conjugate();
+                y1.frobenius_map(3);
+                y2.frobenius_map(2);
+                y1.mul_assign(&y2);
+                y2 = y3;
+                exp_by_x(&mut y2, x);
+                y2.mul_assign(&y0);
+                y2.mul_assign(&r);
+                y1.mul_assign(&y2);
+                y2 = y3;
+                y2.frobenius_map(1);
+                y1.mul_assign(&y2);
+
+                Some(y1)
+            }
+            None => None,
+        }
+    }
+}
+
+impl G2Prepared {
+    pub fn is_zero(&self) -> bool {
+        self.infinity
+    }
+
+    pub fn from_affine(q: G2Affine) -> Self {
+        if q.is_zero() {
+            return G2Prepared {
+                coeffs: vec![],
+                infinity: true,
+            };
+        }
+
+        fn doubling_step(r: &mut G2) -> (Fq2, Fq2, Fq2) {
+            // Adaptation of Algorithm 26, https://eprint.iacr.org/2010/354.pdf
+            let mut tmp0 = r.x;
+            tmp0.square();
+
+            let mut tmp1 = r.y;
+            tmp1.square();
+
+            let mut tmp2 = tmp1;
+            tmp2.square();
+
+            let mut tmp3 = tmp1;
+            tmp3.add_assign(&r.x);
+            tmp3.square();
+            tmp3.sub_assign(&tmp0);
+            tmp3.sub_assign(&tmp2);
+            tmp3.double();
+
+            let mut tmp4 = tmp0;
+            tmp4.double();
+            tmp4.add_assign(&tmp0);
+
+            let mut tmp6 = r.x;
+            tmp6.add_assign(&tmp4);
+
+            let mut tmp5 = tmp4;
+            tmp5.square();
+
+            let mut zsquared = r.z;
+            zsquared.square();
+
+            r.x = tmp5;
+            r.x.sub_assign(&tmp3);
+            r.x.sub_assign(&tmp3);
+
+            r.z.add_assign(&r.y);
+            r.z.square();
+            r.z.sub_assign(&tmp1);
+            r.z.sub_assign(&zsquared);
+
+            r.y = tmp3;
+            r.y.sub_assign(&r.x);
+            r.y.mul_assign(&tmp4);
+
+            tmp2.double();
+            tmp2.double();
+            tmp2.double();
+
+            r.y.sub_assign(&tmp2);
+
+            tmp3 = tmp4;
+            tmp3.mul_assign(&zsquared);
+            tmp3.double();
+            tmp3.negate();
+
+            tmp6.square();
+            tmp6.sub_assign(&tmp0);
+            tmp6.sub_assign(&tmp5);
+
+            tmp1.double();
+            tmp1.double();
+
+            tmp6.sub_assign(&tmp1);
+
+            tmp0 = r.z;
+            tmp0.mul_assign(&zsquared);
+            tmp0.double();
+
+            (tmp0, tmp3, tmp6)
+        }
+
+        fn addition_step(r: &mut G2, q: &G2Affine) -> (Fq2, Fq2, Fq2) {
+            // Adaptation of Algorithm 27, https://eprint.iacr.org/2010/354.pdf
+            let mut zsquared = r.z;
+            zsquared.square();
+
+            let mut ysquared = q.y;
+            ysquared.square();
+
+            let mut t0 = zsquared;
+            t0.mul_assign(&q.x);
+
+            let mut t1 = q.y;
+            t1.add_assign(&r.z);
+            t1.square();
+            t1.sub_assign(&ysquared);
+            t1.sub_assign(&zsquared);
+            t1.mul_assign(&zsquared);
+
+            let mut t2 = t0;
+            t2.sub_assign(&r.x);
+
+            let mut t3 = t2;
+            t3.square();
+
+            let mut t4 = t3;
+            t4.double();
+            t4.double();
+
+            let mut t5 = t4;
+            t5.mul_assign(&t2);
+
+            let mut t6 = t1;
+            t6.sub_assign(&r.y);
+            t6.sub_assign(&r.y);
+
+            let mut t9 = t6;
+            t9.mul_assign(&q.x);
+
+            let mut t7 = t4;
+            t7.mul_assign(&r.x);
+
+            r.x = t6;
+            r.x.square();
+            r.x.sub_assign(&t5);
+            r.x.sub_assign(&t7);
+            r.x.sub_assign(&t7);
+
+            r.z.add_assign(&t2);
+            r.z.square();
+            r.z.sub_assign(&zsquared);
+            r.z.sub_assign(&t3);
+
+            let mut t10 = q.y;
+            t10.add_assign(&r.z);
+
+            let mut t8 = t7;
+            t8.sub_assign(&r.x);
+            t8.mul_assign(&t6);
+
+            t0 = r.y;
+            t0.mul_assign(&t5);
+            t0.double();
+
+            r.y = t8;
+            r.y.sub_assign(&t0);
+
+            t10.square();
+            t10.sub_assign(&ysquared);
+
+            let mut ztsquared = r.z;
+            ztsquared.square();
+
+            t10.sub_assign(&ztsquared);
+
+            t9.double();
+            t9.sub_assign(&t10);
+
+            t10 = r.z;
+            t10.double();
+
+            t6.negate();
+
+            t1 = t6;
+            t1.double();
+
+            (t10, t1, t9)
+        }
+
+        let mut coeffs = vec![];
+        let mut r: G2 = q.into();
+
+        let mut found_one = false;
+        for i in BitIterator::new([BLS_X >> 1]) {
+            if !found_one {
+                found_one = i;
+                continue;
+            }
+
+            coeffs.push(doubling_step(&mut r));
+
+            if i {
+                coeffs.push(addition_step(&mut r, &q));
+            }
+        }
+
+        coeffs.push(doubling_step(&mut r));
+
+        G2Prepared {
+            coeffs,
+            infinity: false,
+        }
+    }
+}
+
+#[test]
+fn bls12_engine_tests() {
+    crate::tests::engine::engine_tests::<Bls12>();
+}

pairing/src/bls12_381/tests/mod.rs

@@ -0,0 +1,614 @@
+use ff::PrimeFieldRepr;
+use group::{CurveAffine, CurveProjective, EncodedPoint, GroupDecodingError};
+
+use super::*;
+use crate::*;
+
+#[test]
+fn test_pairing_result_against_relic() {
+    /*
+    Sent to me from Diego Aranha (author of RELIC library):
+
+    1250EBD871FC0A92 A7B2D83168D0D727 272D441BEFA15C50 3DD8E90CE98DB3E7 B6D194F60839C508 A84305AACA1789B6
+    089A1C5B46E5110B 86750EC6A5323488 68A84045483C92B7 AF5AF689452EAFAB F1A8943E50439F1D 59882A98EAA0170F
+    1368BB445C7C2D20 9703F239689CE34C 0378A68E72A6B3B2 16DA0E22A5031B54 DDFF57309396B38C 881C4C849EC23E87
+    193502B86EDB8857 C273FA075A505129 37E0794E1E65A761 7C90D8BD66065B1F FFE51D7A579973B1 315021EC3C19934F
+    01B2F522473D1713 91125BA84DC4007C FBF2F8DA752F7C74 185203FCCA589AC7 19C34DFFBBAAD843 1DAD1C1FB597AAA5
+    018107154F25A764 BD3C79937A45B845 46DA634B8F6BE14A 8061E55CCEBA478B 23F7DACAA35C8CA7 8BEAE9624045B4B6
+    19F26337D205FB46 9CD6BD15C3D5A04D C88784FBB3D0B2DB DEA54D43B2B73F2C BB12D58386A8703E 0F948226E47EE89D
+    06FBA23EB7C5AF0D 9F80940CA771B6FF D5857BAAF222EB95 A7D2809D61BFE02E 1BFD1B68FF02F0B8 102AE1C2D5D5AB1A
+    11B8B424CD48BF38 FCEF68083B0B0EC5 C81A93B330EE1A67 7D0D15FF7B984E89 78EF48881E32FAC9 1B93B47333E2BA57
+    03350F55A7AEFCD3 C31B4FCB6CE5771C C6A0E9786AB59733 20C806AD36082910 7BA810C5A09FFDD9 BE2291A0C25A99A2
+    04C581234D086A99 02249B64728FFD21 A189E87935A95405 1C7CDBA7B3872629 A4FAFC05066245CB 9108F0242D0FE3EF
+    0F41E58663BF08CF 068672CBD01A7EC7 3BACA4D72CA93544 DEFF686BFD6DF543 D48EAA24AFE47E1E FDE449383B676631
+    */
+
+    assert_eq!(Bls12::pairing(G1::one(), G2::one()), Fq12 {
+        c0: Fq6 {
+            c0: Fq2 {
+                c0: Fq::from_str("2819105605953691245277803056322684086884703000473961065716485506033588504203831029066448642358042597501014294104502").unwrap(),
+                c1: Fq::from_str("1323968232986996742571315206151405965104242542339680722164220900812303524334628370163366153839984196298685227734799").unwrap()
+            },
+            c1: Fq2 {
+                c0: Fq::from_str("2987335049721312504428602988447616328830341722376962214011674875969052835043875658579425548512925634040144704192135").unwrap(),
+                c1: Fq::from_str("3879723582452552452538684314479081967502111497413076598816163759028842927668327542875108457755966417881797966271311").unwrap()
+            },
+            c2: Fq2 {
+                c0: Fq::from_str("261508182517997003171385743374653339186059518494239543139839025878870012614975302676296704930880982238308326681253").unwrap(),
+                c1: Fq::from_str("231488992246460459663813598342448669854473942105054381511346786719005883340876032043606739070883099647773793170614").unwrap()
+            }
+        },
+        c1: Fq6 {
+            c0: Fq2 {
+                c0: Fq::from_str("3993582095516422658773669068931361134188738159766715576187490305611759126554796569868053818105850661142222948198557").unwrap(),
+                c1: Fq::from_str("1074773511698422344502264006159859710502164045911412750831641680783012525555872467108249271286757399121183508900634").unwrap()
+            },
+            c1: Fq2 {
+                c0: Fq::from_str("2727588299083545686739024317998512740561167011046940249988557419323068809019137624943703910267790601287073339193943").unwrap(),
+                c1: Fq::from_str("493643299814437640914745677854369670041080344349607504656543355799077485536288866009245028091988146107059514546594").unwrap()
+            },
+            c2: Fq2 {
+                c0: Fq::from_str("734401332196641441839439105942623141234148957972407782257355060229193854324927417865401895596108124443575283868655").unwrap(),
+                c1: Fq::from_str("2348330098288556420918672502923664952620152483128593484301759394583320358354186482723629999370241674973832318248497").unwrap()
+            }
+        }
+    });
+}
+
+fn test_vectors<G: CurveProjective, E: EncodedPoint<Affine = G::Affine>>(expected: &[u8]) {
+    let mut e = G::zero();
+
+    let mut v = vec![];
+    {
+        let mut expected = expected;
+        for _ in 0..1000 {
+            let e_affine = e.into_affine();
+            let encoded = E::from_affine(e_affine);
+            v.extend_from_slice(encoded.as_ref());
+
+            let mut decoded = E::empty();
+            decoded.as_mut().copy_from_slice(&expected[0..E::size()]);
+            expected = &expected[E::size()..];
+            let decoded = decoded.into_affine().unwrap();
+            assert_eq!(e_affine, decoded);
+
+            e.add_assign(&G::one());
+        }
+    }
+
+    assert_eq!(&v[..], expected);
+}
+
+#[test]
+fn test_g1_uncompressed_valid_vectors() {
+    test_vectors::<G1, G1Uncompressed>(include_bytes!("g1_uncompressed_valid_test_vectors.dat"));
+}
+
+#[test]
+fn test_g1_compressed_valid_vectors() {
+    test_vectors::<G1, G1Compressed>(include_bytes!("g1_compressed_valid_test_vectors.dat"));
+}
+
+#[test]
+fn test_g2_uncompressed_valid_vectors() {
+    test_vectors::<G2, G2Uncompressed>(include_bytes!("g2_uncompressed_valid_test_vectors.dat"));
+}
+
+#[test]
+fn test_g2_compressed_valid_vectors() {
+    test_vectors::<G2, G2Compressed>(include_bytes!("g2_compressed_valid_test_vectors.dat"));
+}
+
+#[test]
+fn test_g1_uncompressed_invalid_vectors() {
+    {
+        let z = G1Affine::zero().into_uncompressed();
+
+        {
+            let mut z = z;
+            z.as_mut()[0] |= 0b1000_0000;
+            if let Err(GroupDecodingError::UnexpectedCompressionMode) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because we expected an uncompressed point");
+            }
+        }
+
+        {
+            let mut z = z;
+            z.as_mut()[0] |= 0b0010_0000;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the parity bit should not be set if the point is at infinity");
+            }
+        }
+
+        for i in 0..G1Uncompressed::size() {
+            let mut z = z;
+            z.as_mut()[i] |= 0b0000_0001;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the coordinates should be zeroes at the point at infinity");
+            }
+        }
+    }
+
+    let o = G1Affine::one().into_uncompressed();
+
+    {
+        let mut o = o;
+        o.as_mut()[0] |= 0b1000_0000;
+        if let Err(GroupDecodingError::UnexpectedCompressionMode) = o.into_affine() {
+            // :)
+        } else {
+            panic!("should have rejected the point because we expected an uncompressed point");
+        }
+    }
+
+    let m = Fq::char();
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[0..]).unwrap();
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "x coordinate");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[48..]).unwrap();
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "y coordinate");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let m = Fq::zero().into_repr();
+
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[0..]).unwrap();
+
+        if let Err(GroupDecodingError::NotOnCurve) = o.into_affine() {
+            // :)
+        } else {
+            panic!("should have rejected the point because it isn't on the curve")
+        }
+    }
+
+    {
+        let mut o = o;
+        let mut x = Fq::one();
+
+        loop {
+            let mut x3b = x;
+            x3b.square();
+            x3b.mul_assign(&x);
+            x3b.add_assign(&Fq::from_repr(FqRepr::from(4)).unwrap()); // TODO: perhaps expose coeff_b through API?
+
+            if let Some(y) = x3b.sqrt() {
+                // We know this is on the curve, but it's likely not going to be in the correct subgroup.
+                x.into_repr().write_be(&mut o.as_mut()[0..]).unwrap();
+                y.into_repr().write_be(&mut o.as_mut()[48..]).unwrap();
+
+                if let Err(GroupDecodingError::NotInSubgroup) = o.into_affine() {
+                    break;
+                } else {
+                    panic!(
+                        "should have rejected the point because it isn't in the correct subgroup"
+                    )
+                }
+            } else {
+                x.add_assign(&Fq::one());
+            }
+        }
+    }
+}
+
+#[test]
+fn test_g2_uncompressed_invalid_vectors() {
+    {
+        let z = G2Affine::zero().into_uncompressed();
+
+        {
+            let mut z = z;
+            z.as_mut()[0] |= 0b1000_0000;
+            if let Err(GroupDecodingError::UnexpectedCompressionMode) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because we expected an uncompressed point");
+            }
+        }
+
+        {
+            let mut z = z;
+            z.as_mut()[0] |= 0b0010_0000;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the parity bit should not be set if the point is at infinity");
+            }
+        }
+
+        for i in 0..G2Uncompressed::size() {
+            let mut z = z;
+            z.as_mut()[i] |= 0b0000_0001;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the coordinates should be zeroes at the point at infinity");
+            }
+        }
+    }
+
+    let o = G2Affine::one().into_uncompressed();
+
+    {
+        let mut o = o;
+        o.as_mut()[0] |= 0b1000_0000;
+        if let Err(GroupDecodingError::UnexpectedCompressionMode) = o.into_affine() {
+            // :)
+        } else {
+            panic!("should have rejected the point because we expected an uncompressed point");
+        }
+    }
+
+    let m = Fq::char();
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[0..]).unwrap();
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "x coordinate (c1)");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[48..]).unwrap();
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "x coordinate (c0)");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[96..]).unwrap();
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "y coordinate (c1)");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[144..]).unwrap();
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "y coordinate (c0)");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let m = Fq::zero().into_repr();
+
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[0..]).unwrap();
+        m.write_be(&mut o.as_mut()[48..]).unwrap();
+
+        if let Err(GroupDecodingError::NotOnCurve) = o.into_affine() {
+            // :)
+        } else {
+            panic!("should have rejected the point because it isn't on the curve")
+        }
+    }
+
+    {
+        let mut o = o;
+        let mut x = Fq2::one();
+
+        loop {
+            let mut x3b = x;
+            x3b.square();
+            x3b.mul_assign(&x);
+            x3b.add_assign(&Fq2 {
+                c0: Fq::from_repr(FqRepr::from(4)).unwrap(),
+                c1: Fq::from_repr(FqRepr::from(4)).unwrap(),
+            }); // TODO: perhaps expose coeff_b through API?
+
+            if let Some(y) = x3b.sqrt() {
+                // We know this is on the curve, but it's likely not going to be in the correct subgroup.
+                x.c1.into_repr().write_be(&mut o.as_mut()[0..]).unwrap();
+                x.c0.into_repr().write_be(&mut o.as_mut()[48..]).unwrap();
+                y.c1.into_repr().write_be(&mut o.as_mut()[96..]).unwrap();
+                y.c0.into_repr().write_be(&mut o.as_mut()[144..]).unwrap();
+
+                if let Err(GroupDecodingError::NotInSubgroup) = o.into_affine() {
+                    break;
+                } else {
+                    panic!(
+                        "should have rejected the point because it isn't in the correct subgroup"
+                    )
+                }
+            } else {
+                x.add_assign(&Fq2::one());
+            }
+        }
+    }
+}
+
+#[test]
+fn test_g1_compressed_invalid_vectors() {
+    {
+        let z = G1Affine::zero().into_compressed();
+
+        {
+            let mut z = z;
+            z.as_mut()[0] &= 0b0111_1111;
+            if let Err(GroupDecodingError::UnexpectedCompressionMode) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because we expected a compressed point");
+            }
+        }
+
+        {
+            let mut z = z;
+            z.as_mut()[0] |= 0b0010_0000;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the parity bit should not be set if the point is at infinity");
+            }
+        }
+
+        for i in 0..G1Compressed::size() {
+            let mut z = z;
+            z.as_mut()[i] |= 0b0000_0001;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the coordinates should be zeroes at the point at infinity");
+            }
+        }
+    }
+
+    let o = G1Affine::one().into_compressed();
+
+    {
+        let mut o = o;
+        o.as_mut()[0] &= 0b0111_1111;
+        if let Err(GroupDecodingError::UnexpectedCompressionMode) = o.into_affine() {
+            // :)
+        } else {
+            panic!("should have rejected the point because we expected a compressed point");
+        }
+    }
+
+    let m = Fq::char();
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[0..]).unwrap();
+        o.as_mut()[0] |= 0b1000_0000;
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "x coordinate");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        let mut x = Fq::one();
+
+        loop {
+            let mut x3b = x;
+            x3b.square();
+            x3b.mul_assign(&x);
+            x3b.add_assign(&Fq::from_repr(FqRepr::from(4)).unwrap()); // TODO: perhaps expose coeff_b through API?
+
+            if let Some(_) = x3b.sqrt() {
+                x.add_assign(&Fq::one());
+            } else {
+                x.into_repr().write_be(&mut o.as_mut()[0..]).unwrap();
+                o.as_mut()[0] |= 0b1000_0000;
+
+                if let Err(GroupDecodingError::NotOnCurve) = o.into_affine() {
+                    break;
+                } else {
+                    panic!("should have rejected the point because it isn't on the curve")
+                }
+            }
+        }
+    }
+
+    {
+        let mut o = o;
+        let mut x = Fq::one();
+
+        loop {
+            let mut x3b = x;
+            x3b.square();
+            x3b.mul_assign(&x);
+            x3b.add_assign(&Fq::from_repr(FqRepr::from(4)).unwrap()); // TODO: perhaps expose coeff_b through API?
+
+            if let Some(_) = x3b.sqrt() {
+                // We know this is on the curve, but it's likely not going to be in the correct subgroup.
+                x.into_repr().write_be(&mut o.as_mut()[0..]).unwrap();
+                o.as_mut()[0] |= 0b1000_0000;
+
+                if let Err(GroupDecodingError::NotInSubgroup) = o.into_affine() {
+                    break;
+                } else {
+                    panic!(
+                        "should have rejected the point because it isn't in the correct subgroup"
+                    )
+                }
+            } else {
+                x.add_assign(&Fq::one());
+            }
+        }
+    }
+}
+
+#[test]
+fn test_g2_compressed_invalid_vectors() {
+    {
+        let z = G2Affine::zero().into_compressed();
+
+        {
+            let mut z = z;
+            z.as_mut()[0] &= 0b0111_1111;
+            if let Err(GroupDecodingError::UnexpectedCompressionMode) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because we expected a compressed point");
+            }
+        }
+
+        {
+            let mut z = z;
+            z.as_mut()[0] |= 0b0010_0000;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the parity bit should not be set if the point is at infinity");
+            }
+        }
+
+        for i in 0..G2Compressed::size() {
+            let mut z = z;
+            z.as_mut()[i] |= 0b0000_0001;
+            if let Err(GroupDecodingError::UnexpectedInformation) = z.into_affine() {
+                // :)
+            } else {
+                panic!("should have rejected the point because the coordinates should be zeroes at the point at infinity");
+            }
+        }
+    }
+
+    let o = G2Affine::one().into_compressed();
+
+    {
+        let mut o = o;
+        o.as_mut()[0] &= 0b0111_1111;
+        if let Err(GroupDecodingError::UnexpectedCompressionMode) = o.into_affine() {
+            // :)
+        } else {
+            panic!("should have rejected the point because we expected a compressed point");
+        }
+    }
+
+    let m = Fq::char();
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[0..]).unwrap();
+        o.as_mut()[0] |= 0b1000_0000;
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "x coordinate (c1)");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        m.write_be(&mut o.as_mut()[48..]).unwrap();
+        o.as_mut()[0] |= 0b1000_0000;
+
+        if let Err(GroupDecodingError::CoordinateDecodingError(coordinate, _)) = o.into_affine() {
+            assert_eq!(coordinate, "x coordinate (c0)");
+        } else {
+            panic!("should have rejected the point")
+        }
+    }
+
+    {
+        let mut o = o;
+        let mut x = Fq2 {
+            c0: Fq::one(),
+            c1: Fq::one(),
+        };
+
+        loop {
+            let mut x3b = x;
+            x3b.square();
+            x3b.mul_assign(&x);
+            x3b.add_assign(&Fq2 {
+                c0: Fq::from_repr(FqRepr::from(4)).unwrap(),
+                c1: Fq::from_repr(FqRepr::from(4)).unwrap(),
+            }); // TODO: perhaps expose coeff_b through API?
+
+            if let Some(_) = x3b.sqrt() {
+                x.add_assign(&Fq2::one());
+            } else {
+                x.c1.into_repr().write_be(&mut o.as_mut()[0..]).unwrap();
+                x.c0.into_repr().write_be(&mut o.as_mut()[48..]).unwrap();
+                o.as_mut()[0] |= 0b1000_0000;
+
+                if let Err(GroupDecodingError::NotOnCurve) = o.into_affine() {
+                    break;
+                } else {
+                    panic!("should have rejected the point because it isn't on the curve")
+                }
+            }
+        }
+    }
+
+    {
+        let mut o = o;
+        let mut x = Fq2 {
+            c0: Fq::one(),
+            c1: Fq::one(),
+        };
+
+        loop {
+            let mut x3b = x;
+            x3b.square();
+            x3b.mul_assign(&x);
+            x3b.add_assign(&Fq2 {
+                c0: Fq::from_repr(FqRepr::from(4)).unwrap(),
+                c1: Fq::from_repr(FqRepr::from(4)).unwrap(),
+            }); // TODO: perhaps expose coeff_b through API?
+
+            if let Some(_) = x3b.sqrt() {
+                // We know this is on the curve, but it's likely not going to be in the correct subgroup.
+                x.c1.into_repr().write_be(&mut o.as_mut()[0..]).unwrap();
+                x.c0.into_repr().write_be(&mut o.as_mut()[48..]).unwrap();
+                o.as_mut()[0] |= 0b1000_0000;
+
+                if let Err(GroupDecodingError::NotInSubgroup) = o.into_affine() {
+                    break;
+                } else {
+                    panic!(
+                        "should have rejected the point because it isn't in the correct subgroup"
+                    )
+                }
+            } else {
+                x.add_assign(&Fq2::one());
+            }
+        }
+    }
+}

pairing/src/lib.rs

@@ -0,0 +1,113 @@
+//! A library for working with pairing-friendly curves.
+
+// `clippy` is a code linting tool for improving code quality by catching
+// common mistakes or strange code patterns. If the `cargo-clippy` feature
+// is provided, all compiler warnings are prohibited.
+#![cfg_attr(feature = "cargo-clippy", deny(warnings))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::inline_always))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::too_many_arguments))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::unreadable_literal))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::many_single_char_names))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::new_without_default))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::write_literal))]
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+// Force public structures to implement Debug
+#![deny(missing_debug_implementations)]
+
+#[cfg(test)]
+pub mod tests;
+
+pub mod bls12_381;
+
+use ff::{Field, PrimeField, ScalarEngine, SqrtField};
+use group::{CurveAffine, CurveProjective};
+
+/// An "engine" is a collection of types (fields, elliptic curve groups, etc.)
+/// with well-defined relationships. In particular, the G1/G2 curve groups are
+/// of prime order `r`, and are equipped with a bilinear pairing function.
+pub trait Engine: ScalarEngine {
+    /// The projective representation of an element in G1.
+    type G1: CurveProjective<
+            Engine = Self,
+            Base = Self::Fq,
+            Scalar = Self::Fr,
+            Affine = Self::G1Affine,
+        > + From<Self::G1Affine>;
+
+    /// The affine representation of an element in G1.
+    type G1Affine: PairingCurveAffine<
+            Engine = Self,
+            Base = Self::Fq,
+            Scalar = Self::Fr,
+            Projective = Self::G1,
+            Pair = Self::G2Affine,
+            PairingResult = Self::Fqk,
+        > + From<Self::G1>;
+
+    /// The projective representation of an element in G2.
+    type G2: CurveProjective<
+            Engine = Self,
+            Base = Self::Fqe,
+            Scalar = Self::Fr,
+            Affine = Self::G2Affine,
+        > + From<Self::G2Affine>;
+
+    /// The affine representation of an element in G2.
+    type G2Affine: PairingCurveAffine<
+            Engine = Self,
+            Base = Self::Fqe,
+            Scalar = Self::Fr,
+            Projective = Self::G2,
+            Pair = Self::G1Affine,
+            PairingResult = Self::Fqk,
+        > + From<Self::G2>;
+
+    /// The base field that hosts G1.
+    type Fq: PrimeField + SqrtField;
+
+    /// The extension field that hosts G2.
+    type Fqe: SqrtField;
+
+    /// The extension field that hosts the target group of the pairing.
+    type Fqk: Field;
+
+    /// Perform a miller loop with some number of (G1, G2) pairs.
+    fn miller_loop<'a, I>(i: I) -> Self::Fqk
+    where
+        I: IntoIterator<
+            Item = &'a (
+                &'a <Self::G1Affine as PairingCurveAffine>::Prepared,
+                &'a <Self::G2Affine as PairingCurveAffine>::Prepared,
+            ),
+        >;
+
+    /// Perform final exponentiation of the result of a miller loop.
+    fn final_exponentiation(_: &Self::Fqk) -> Option<Self::Fqk>;
+
+    /// Performs a complete pairing operation `(p, q)`.
+    fn pairing<G1, G2>(p: G1, q: G2) -> Self::Fqk
+    where
+        G1: Into<Self::G1Affine>,
+        G2: Into<Self::G2Affine>,
+    {
+        Self::final_exponentiation(&Self::miller_loop(
+            [(&(p.into().prepare()), &(q.into().prepare()))].iter(),
+        ))
+        .unwrap()
+    }
+}
+
+/// Affine representation of an elliptic curve point that can be used
+/// to perform pairings.
+pub trait PairingCurveAffine: CurveAffine {
+    type Prepared: Clone + Send + Sync + 'static;
+    type Pair: PairingCurveAffine<Pair = Self>;
+    type PairingResult: Field;
+
+    /// Prepares this element for pairing purposes.
+    fn prepare(&self) -> Self::Prepared;
+
+    /// Perform a pairing
+    fn pairing_with(&self, other: &Self::Pair) -> Self::PairingResult;
+}

pairing/src/tests/engine.rs

@@ -0,0 +1,137 @@
+use group::{CurveAffine, CurveProjective};
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+use crate::{Engine, Field, PairingCurveAffine, PrimeField};
+
+pub fn engine_tests<E: Engine>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..10 {
+        let a = E::G1::random(&mut rng).into_affine();
+        let b = E::G2::random(&mut rng).into_affine();
+
+        assert!(a.pairing_with(&b) == b.pairing_with(&a));
+        assert!(a.pairing_with(&b) == E::pairing(a, b));
+    }
+
+    for _ in 0..1000 {
+        let z1 = E::G1Affine::zero().prepare();
+        let z2 = E::G2Affine::zero().prepare();
+
+        let a = E::G1::random(&mut rng).into_affine().prepare();
+        let b = E::G2::random(&mut rng).into_affine().prepare();
+        let c = E::G1::random(&mut rng).into_affine().prepare();
+        let d = E::G2::random(&mut rng).into_affine().prepare();
+
+        assert_eq!(
+            E::Fqk::one(),
+            E::final_exponentiation(&E::miller_loop(&[(&z1, &b)])).unwrap()
+        );
+
+        assert_eq!(
+            E::Fqk::one(),
+            E::final_exponentiation(&E::miller_loop(&[(&a, &z2)])).unwrap()
+        );
+
+        assert_eq!(
+            E::final_exponentiation(&E::miller_loop(&[(&z1, &b), (&c, &d)])).unwrap(),
+            E::final_exponentiation(&E::miller_loop(&[(&a, &z2), (&c, &d)])).unwrap()
+        );
+
+        assert_eq!(
+            E::final_exponentiation(&E::miller_loop(&[(&a, &b), (&z1, &d)])).unwrap(),
+            E::final_exponentiation(&E::miller_loop(&[(&a, &b), (&c, &z2)])).unwrap()
+        );
+    }
+
+    random_bilinearity_tests::<E>();
+    random_miller_loop_tests::<E>();
+}
+
+fn random_miller_loop_tests<E: Engine>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    // Exercise the miller loop for a reduced pairing
+    for _ in 0..1000 {
+        let a = E::G1::random(&mut rng);
+        let b = E::G2::random(&mut rng);
+
+        let p2 = E::pairing(a, b);
+
+        let a = a.into_affine().prepare();
+        let b = b.into_affine().prepare();
+
+        let p1 = E::final_exponentiation(&E::miller_loop(&[(&a, &b)])).unwrap();
+
+        assert_eq!(p1, p2);
+    }
+
+    // Exercise a double miller loop
+    for _ in 0..1000 {
+        let a = E::G1::random(&mut rng);
+        let b = E::G2::random(&mut rng);
+        let c = E::G1::random(&mut rng);
+        let d = E::G2::random(&mut rng);
+
+        let ab = E::pairing(a, b);
+        let cd = E::pairing(c, d);
+
+        let mut abcd = ab;
+        abcd.mul_assign(&cd);
+
+        let a = a.into_affine().prepare();
+        let b = b.into_affine().prepare();
+        let c = c.into_affine().prepare();
+        let d = d.into_affine().prepare();
+
+        let abcd_with_double_loop =
+            E::final_exponentiation(&E::miller_loop(&[(&a, &b), (&c, &d)])).unwrap();
+
+        assert_eq!(abcd, abcd_with_double_loop);
+    }
+}
+
+fn random_bilinearity_tests<E: Engine>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let a = E::G1::random(&mut rng);
+        let b = E::G2::random(&mut rng);
+
+        let c = E::Fr::random(&mut rng);
+        let d = E::Fr::random(&mut rng);
+
+        let mut ac = a;
+        ac.mul_assign(c);
+
+        let mut ad = a;
+        ad.mul_assign(d);
+
+        let mut bc = b;
+        bc.mul_assign(c);
+
+        let mut bd = b;
+        bd.mul_assign(d);
+
+        let acbd = E::pairing(ac, bd);
+        let adbc = E::pairing(ad, bc);
+
+        let mut cd = c;
+        cd.mul_assign(&d);
+
+        let abcd = E::pairing(a, b).pow(cd.into_repr());
+
+        assert_eq!(acbd, adbc);
+        assert_eq!(acbd, abcd);
+    }
+}

pairing/src/tests/field.rs

@@ -0,0 +1,279 @@
+use ff::{Field, LegendreSymbol, PrimeField, SqrtField};
+use rand_core::{RngCore, SeedableRng};
+use rand_xorshift::XorShiftRng;
+
+pub fn random_frobenius_tests<F: Field, C: AsRef<[u64]>>(characteristic: C, maxpower: usize) {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..100 {
+        for i in 0..(maxpower + 1) {
+            let mut a = F::random(&mut rng);
+            let mut b = a;
+
+            for _ in 0..i {
+                a = a.pow(&characteristic);
+            }
+            b.frobenius_map(i);
+
+            assert_eq!(a, b);
+        }
+    }
+}
+
+pub fn random_sqrt_tests<F: SqrtField>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..10000 {
+        let a = F::random(&mut rng);
+        let mut b = a;
+        b.square();
+        assert_eq!(b.legendre(), LegendreSymbol::QuadraticResidue);
+
+        let b = b.sqrt().unwrap();
+        let mut negb = b;
+        negb.negate();
+
+        assert!(a == b || a == negb);
+    }
+
+    let mut c = F::one();
+    for _ in 0..10000 {
+        let mut b = c;
+        b.square();
+        assert_eq!(b.legendre(), LegendreSymbol::QuadraticResidue);
+
+        b = b.sqrt().unwrap();
+
+        if b != c {
+            b.negate();
+        }
+
+        assert_eq!(b, c);
+
+        c.add_assign(&F::one());
+    }
+}
+
+pub fn random_field_tests<F: Field>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    random_multiplication_tests::<F, _>(&mut rng);
+    random_addition_tests::<F, _>(&mut rng);
+    random_subtraction_tests::<F, _>(&mut rng);
+    random_negation_tests::<F, _>(&mut rng);
+    random_doubling_tests::<F, _>(&mut rng);
+    random_squaring_tests::<F, _>(&mut rng);
+    random_inversion_tests::<F, _>(&mut rng);
+    random_expansion_tests::<F, _>(&mut rng);
+
+    assert!(F::zero().is_zero());
+    {
+        let mut z = F::zero();
+        z.negate();
+        assert!(z.is_zero());
+    }
+
+    assert!(F::zero().inverse().is_none());
+
+    // Multiplication by zero
+    {
+        let mut a = F::random(&mut rng);
+        a.mul_assign(&F::zero());
+        assert!(a.is_zero());
+    }
+
+    // Addition by zero
+    {
+        let mut a = F::random(&mut rng);
+        let copy = a;
+        a.add_assign(&F::zero());
+        assert_eq!(a, copy);
+    }
+}
+
+pub fn from_str_tests<F: PrimeField>() {
+    {
+        let a = "84395729384759238745923745892374598234705297301958723458712394587103249587213984572934750213947582345792304758273458972349582734958273495872304598234";
+        let b = "38495729084572938457298347502349857029384609283450692834058293405982304598230458230495820394850293845098234059823049582309485203948502938452093482039";
+        let c = "3248875134290623212325429203829831876024364170316860259933542844758450336418538569901990710701240661702808867062612075657861768196242274635305077449545396068598317421057721935408562373834079015873933065667961469731886739181625866970316226171512545167081793907058686908697431878454091011239990119126";
+
+        let mut a = F::from_str(a).unwrap();
+        let b = F::from_str(b).unwrap();
+        let c = F::from_str(c).unwrap();
+
+        a.mul_assign(&b);
+
+        assert_eq!(a, c);
+    }
+
+    {
+        let mut rng = XorShiftRng::from_seed([
+            0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06,
+            0xbc, 0xe5,
+        ]);
+
+        for _ in 0..1000 {
+            let n = rng.next_u64();
+
+            let a = F::from_str(&format!("{}", n)).unwrap();
+            let b = F::from_repr(n.into()).unwrap();
+
+            assert_eq!(a, b);
+        }
+    }
+
+    assert!(F::from_str("").is_none());
+    assert!(F::from_str("0").unwrap().is_zero());
+    assert!(F::from_str("00").is_none());
+    assert!(F::from_str("00000000000").is_none());
+}
+
+fn random_multiplication_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        let a = F::random(rng);
+        let b = F::random(rng);
+        let c = F::random(rng);
+
+        let mut t0 = a; // (a * b) * c
+        t0.mul_assign(&b);
+        t0.mul_assign(&c);
+
+        let mut t1 = a; // (a * c) * b
+        t1.mul_assign(&c);
+        t1.mul_assign(&b);
+
+        let mut t2 = b; // (b * c) * a
+        t2.mul_assign(&c);
+        t2.mul_assign(&a);
+
+        assert_eq!(t0, t1);
+        assert_eq!(t1, t2);
+    }
+}
+
+fn random_addition_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        let a = F::random(rng);
+        let b = F::random(rng);
+        let c = F::random(rng);
+
+        let mut t0 = a; // (a + b) + c
+        t0.add_assign(&b);
+        t0.add_assign(&c);
+
+        let mut t1 = a; // (a + c) + b
+        t1.add_assign(&c);
+        t1.add_assign(&b);
+
+        let mut t2 = b; // (b + c) + a
+        t2.add_assign(&c);
+        t2.add_assign(&a);
+
+        assert_eq!(t0, t1);
+        assert_eq!(t1, t2);
+    }
+}
+
+fn random_subtraction_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        let b = F::random(rng);
+        let a = F::random(rng);
+
+        let mut t0 = a; // (a - b)
+        t0.sub_assign(&b);
+
+        let mut t1 = b; // (b - a)
+        t1.sub_assign(&a);
+
+        let mut t2 = t0; // (a - b) + (b - a) = 0
+        t2.add_assign(&t1);
+
+        assert!(t2.is_zero());
+    }
+}
+
+fn random_negation_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        let a = F::random(rng);
+        let mut b = a;
+        b.negate();
+        b.add_assign(&a);
+
+        assert!(b.is_zero());
+    }
+}
+
+fn random_doubling_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        let mut a = F::random(rng);
+        let mut b = a;
+        a.add_assign(&b);
+        b.double();
+
+        assert_eq!(a, b);
+    }
+}
+
+fn random_squaring_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        let mut a = F::random(rng);
+        let mut b = a;
+        a.mul_assign(&b);
+        b.square();
+
+        assert_eq!(a, b);
+    }
+}
+
+fn random_inversion_tests<F: Field, R: RngCore>(rng: &mut R) {
+    assert!(F::zero().inverse().is_none());
+
+    for _ in 0..10000 {
+        let mut a = F::random(rng);
+        let b = a.inverse().unwrap(); // probablistically nonzero
+        a.mul_assign(&b);
+
+        assert_eq!(a, F::one());
+    }
+}
+
+fn random_expansion_tests<F: Field, R: RngCore>(rng: &mut R) {
+    for _ in 0..10000 {
+        // Compare (a + b)(c + d) and (a*c + b*c + a*d + b*d)
+
+        let a = F::random(rng);
+        let b = F::random(rng);
+        let c = F::random(rng);
+        let d = F::random(rng);
+
+        let mut t0 = a;
+        t0.add_assign(&b);
+        let mut t1 = c;
+        t1.add_assign(&d);
+        t0.mul_assign(&t1);
+
+        let mut t2 = a;
+        t2.mul_assign(&c);
+        let mut t3 = b;
+        t3.mul_assign(&c);
+        let mut t4 = a;
+        t4.mul_assign(&d);
+        let mut t5 = b;
+        t5.mul_assign(&d);
+
+        t2.add_assign(&t3);
+        t2.add_assign(&t4);
+        t2.add_assign(&t5);
+
+        assert_eq!(t0, t2);
+    }
+}

pairing/src/tests/mod.rs

@@ -0,0 +1,3 @@
+pub mod engine;
+pub mod field;
+pub mod repr;

pairing/src/tests/repr.rs

@@ -0,0 +1,108 @@
+use ff::{PrimeField, PrimeFieldRepr};
+use rand_core::SeedableRng;
+use rand_xorshift::XorShiftRng;
+
+pub fn random_repr_tests<P: PrimeField>() {
+    random_encoding_tests::<P>();
+    random_shl_tests::<P>();
+    random_shr_tests::<P>();
+}
+
+fn random_encoding_tests<P: PrimeField>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..1000 {
+        let r = P::random(&mut rng).into_repr();
+
+        // Big endian
+        {
+            let mut rdecoded = <P as PrimeField>::Repr::default();
+
+            let mut v: Vec<u8> = vec![];
+            r.write_be(&mut v).unwrap();
+            rdecoded.read_be(&v[0..]).unwrap();
+
+            assert_eq!(r, rdecoded);
+        }
+
+        // Little endian
+        {
+            let mut rdecoded = <P as PrimeField>::Repr::default();
+
+            let mut v: Vec<u8> = vec![];
+            r.write_le(&mut v).unwrap();
+            rdecoded.read_le(&v[0..]).unwrap();
+
+            assert_eq!(r, rdecoded);
+        }
+
+        {
+            let mut rdecoded_le = <P as PrimeField>::Repr::default();
+            let mut rdecoded_be_flip = <P as PrimeField>::Repr::default();
+
+            let mut v: Vec<u8> = vec![];
+            r.write_le(&mut v).unwrap();
+
+            // This reads in little-endian, so we are done.
+            rdecoded_le.read_le(&v[..]).unwrap();
+
+            // This reads in big-endian, so we perform a swap of the
+            // bytes beforehand.
+            let v: Vec<u8> = v.into_iter().rev().collect();
+            rdecoded_be_flip.read_be(&v[..]).unwrap();
+
+            assert_eq!(rdecoded_le, rdecoded_be_flip);
+        }
+    }
+}
+
+fn random_shl_tests<P: PrimeField>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..100 {
+        let r = P::random(&mut rng).into_repr();
+
+        for shift in 0..(r.num_bits() + 1) {
+            let mut r1 = r;
+            let mut r2 = r;
+
+            for _ in 0..shift {
+                r1.mul2();
+            }
+
+            r2.shl(shift);
+
+            assert_eq!(r1, r2);
+        }
+    }
+}
+
+fn random_shr_tests<P: PrimeField>() {
+    let mut rng = XorShiftRng::from_seed([
+        0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
+        0xe5,
+    ]);
+
+    for _ in 0..100 {
+        let r = P::random(&mut rng).into_repr();
+
+        for shift in 0..(r.num_bits() + 1) {
+            let mut r1 = r;
+            let mut r2 = r;
+
+            for _ in 0..shift {
+                r1.div2();
+            }
+
+            r2.shr(shift);
+
+            assert_eq!(r1, r2);
+        }
+    }
+}

zcash_client_backend/.gitignore

@@ -0,0 +1,2 @@
+# Protobufs
+src/proto/

zcash_client_backend/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "zcash_client_backend"
+description = "APIs for creating shielded Zcash light clients"
+version = "0.1.0"
+authors = [
+    "Jack Grigg <jack@z.cash>",
+]
+homepage = "https://github.com/zcash/librustzcash"
+repository = "https://github.com/zcash/librustzcash"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+edition = "2018"
+
+[dependencies]
+bech32 = "0.7"
+ff = { version = "0.5.0", path = "../ff" }
+hex = "0.3"
+pairing = { version = "0.15.0", path = "../pairing" }
+protobuf = "2"
+subtle = "2"
+zcash_primitives = { version = "0.1.0", path = "../zcash_primitives" }
+
+[build-dependencies]
+protobuf-codegen-pure = "2"
+
+[dev-dependencies]
+rand_core = "0.5"
+rand_xorshift = "0.2"
+
+[badges]
+maintenance = { status = "actively-developed" }

zcash_client_backend/LICENSE-APACHE

@@ -0,0 +1,202 @@
+                              Apache License
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+
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+

zcash_client_backend/LICENSE-MIT

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2017-2019 Electric Coin Company
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.