Fix hash to scalar

Resolves #3

CHANGELOG.md

@@ -7,13 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Change the implementation for hashing a slice of bytes into a BlsScalar to `BlsScalar::hash_to_scalar` [#3]
+
 ## [0.1.0] - 2024-01-08
 
 ### Added
 
 - Add initial commit, this package continues the development of [dusk-bls12_381-sign](https://github.com/dusk-network/bls12_381-sign/) at version `0.6.0` under the new name: `bls12_381-bls` and without the go related code.
 
 <!-- ISSUES -->
+[#3]: https://github.com/dusk-network/bls12_381-bls/issues/3
 
 <!-- VERSIONS -->
 [Unreleased]: https://github.com/dusk-network/bls12_381-bls/compare/v0.1.0...HEAD

Cargo.toml

@@ -15,7 +15,6 @@ exclude = [
 license = "MPL-2.0"
 
 [dependencies]
-blake2 = { version = "0.10", default-features = false }
 dusk-bls12_381 = { version = "0.13", default-features = false, features = ["alloc", "pairings"] }
 dusk-bytes = "0.1"
 rand_core = { version = "0.6", default-features = false }

src/hash.rs

@@ -8,35 +8,20 @@
 
 use crate::PublicKey;
 
-use blake2::digest::consts::U32;
-use blake2::Digest;
 use dusk_bls12_381::{BlsScalar, G1Affine};
 use dusk_bytes::Serializable;
 
-type Blake2b = blake2::Blake2b<U32>;
-
-/// Hash an arbitrary slice of bytes into a [`BlsScalar`]
-fn h(msg: &[u8]) -> BlsScalar {
-    let mut digest: [u8; BlsScalar::SIZE] = Blake2b::digest(msg).into();
-
-    // Truncate the contract id to fit bls
-    digest[31] &= 0x3f;
-
-    let hash: Option<BlsScalar> = BlsScalar::from_bytes(&digest).into();
-    hash.unwrap_or_default()
-}
-
 /// h0 is the hash-to-curve-point function.
 /// Hₒ : M -> Gₒ
 pub fn h0(msg: &[u8]) -> G1Affine {
     // Now multiply this message by the G1 base point,
     // to generate a G1Affine.
-    (G1Affine::generator() * h(msg)).into()
+    (G1Affine::generator() * BlsScalar::hash_to_scalar(msg)).into()
 }
 
 /// h1 is the hashing function used in the modified BLS
 /// multi-signature construction.
 /// H₁ : G₂ -> R
 pub fn h1(pk: &PublicKey) -> BlsScalar {
-    h(&pk.to_bytes())
+    BlsScalar::hash_to_scalar(&pk.to_bytes())
 }