poanetwork
/
threshold_crypto
mirror of https://github.com/poanetwork/threshold_crypto.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Simplify hash_g2.

This commit is contained in:
Andreas Fackler 2018-05-29 21:59:21 +02:00 committed by Vladimir Komendantskiy
parent c830e8f605
commit 12516d2716
1 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
mod.rs
View File

@ -1,6 +1,7 @@
mod error;
use byteorder::{BigEndian, ByteOrder};
use init_with::InitWith;
use pairing::{CurveAffine, CurveProjective, Engine, Field, PrimeField};
use rand::{ChaChaRng, Rand, Rng, SeedableRng};
@ -8,6 +9,9 @@ use ring::digest;
use self::error::{ErrorKind, Result};
/// The number of words (`u32`) in a ChaCha RNG seed.
const CHACHA_RNG_SEED_SIZE: usize = 8;
/// Returns a hash of the given message in `G2`.
pub fn hash_g2<E, M>(msg: M) -> E::G2
where
@ -16,14 +20,10 @@ where
M: AsRef<[u8]>,
{
let digest = digest::digest(&digest::SHA256, msg.as_ref());
// The `pairing` crate's `G2` implements `Rand`. We initialize a seedable RNG with the SHA256
// digest, and use it to generate the element.
let mut msg_u32: Vec<u32> = Vec::with_capacity(256 / 32);
for chunk in digest.as_ref().chunks(4) {
let word = BigEndian::read_u32(chunk);
msg_u32.push(word);
}
let mut rng = ChaChaRng::from_seed(&msg_u32);
let seed = <[u32; CHACHA_RNG_SEED_SIZE]>::init_with_indices(|i| {
BigEndian::read_u32(&digest.as_ref()[(4 * i)..(4 * i + 4)])
});
let mut rng = ChaChaRng::from_seed(&seed);
rng.gen()
}