Add 'sapling-crypto/' from commit '21084bde2019c04bd34208e63c3560fe2c02fb0e'

git-subtree-dir: sapling-crypto
git-subtree-mainline: 9f748554d0
git-subtree-split: 21084bde20

sapling-crypto/src/util.rs

@@ -0,0 +1,11 @@
+use blake2_rfc::blake2b::Blake2b;
+
+use jubjub::{JubjubEngine, ToUniform};
+
+pub fn hash_to_scalar<E: JubjubEngine>(persona: &[u8], a: &[u8], b: &[u8]) -> E::Fs {
+    let mut hasher = Blake2b::with_params(64, &[], &[], persona);
+    hasher.update(a);
+    hasher.update(b);
+    let ret = hasher.finalize();
+    E::Fs::to_uniform(ret.as_ref())
+}