999dcbfcab
The primary reason for migrating is that these crates provide APIs for setting the personalisation string. This enables us to depend solely on published crates, and thus publish our own crates. The SIMD implementations are ported from libsodium. Closes #67.
49 lines
1022 B
Rust
49 lines
1022 B
Rust
use jubjub::{
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JubjubEngine,
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PrimeOrder,
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edwards
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};
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use ff::{
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PrimeField
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};
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use blake2s_simd::Params;
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use constants;
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/// Produces a random point in the Jubjub curve.
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/// The point is guaranteed to be prime order
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/// and not the identity.
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pub fn group_hash<E: JubjubEngine>(
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tag: &[u8],
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personalization: &[u8],
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params: &E::Params
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) -> Option<edwards::Point<E, PrimeOrder>>
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{
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assert_eq!(personalization.len(), 8);
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// Check to see that scalar field is 255 bits
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assert!(E::Fr::NUM_BITS == 255);
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let h = Params::new()
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.hash_length(32)
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.personal(personalization)
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.to_state()
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.update(constants::GH_FIRST_BLOCK)
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.update(tag)
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.finalize();
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match edwards::Point::<E, _>::read(h.as_ref(), params) {
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Ok(p) => {
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let p = p.mul_by_cofactor(params);
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if p != edwards::Point::zero() {
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Some(p)
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} else {
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None
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}
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},
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Err(_) => None
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}
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}
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