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Cleaned up the hash implementation a bit.

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This commit is contained in:
Nathan Vegdahl 2020-02-24 13:09:49 +09:00
parent dc9b3dd5c3
commit 4e435732d7
1 changed files with 19 additions and 18 deletions
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37
sub_crates/backend/src/hash.rs
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@ -82,12 +82,12 @@ impl LedHash256 {
mix(&mut self.state[..], &[self.message_length * 8, 0, 0, 0]);
// Get the digest as a byte array and return it.
let mut result = [0u8; BLOCK_SIZE];
result[0..8].copy_from_slice(&self.state[0].to_le_bytes());
result[8..16].copy_from_slice(&self.state[1].to_le_bytes());
result[16..24].copy_from_slice(&self.state[2].to_le_bytes());
result[24..32].copy_from_slice(&self.state[3].to_le_bytes());
return result;
let mut digest = [0u8; BLOCK_SIZE];
digest[0..8].copy_from_slice(&self.state[0].to_le_bytes());
digest[8..16].copy_from_slice(&self.state[1].to_le_bytes());
digest[16..24].copy_from_slice(&self.state[2].to_le_bytes());
digest[24..32].copy_from_slice(&self.state[3].to_le_bytes());
return digest;
}
fn mix_buffer_into_state(&mut self) {
@ -100,9 +100,9 @@ impl LedHash256 {
/// The main mix function. Mixes a block into the hash state.
///
/// Inspired by Skein 1.3, and using the constants from its 256-bit
/// variant. It does 9 rounds of mixing, as that produces full
/// diffusion for 256-bit keys according to the Skein 1.3 paper.
/// Inspired by Skein 1.3, and using its MIX function and its constants.
/// This does 9 rounds of mixing, as that produces full diffusion for
/// 256-bit state according to the Skein 1.3 paper.
///
/// The mix rotation constants, as taken from Skein 1.3 256-bit variant:
/// 14 16
@ -119,12 +119,6 @@ impl LedHash256 {
/// Indices: 0 1 2 3
/// Become: 0 3 2 1
fn mix(state: &mut [u64], block: &[u64]) {
/// The MIX function from Skein.
fn umix(pair: &mut [u64], r: u32) {
pair[0] = pair[0].wrapping_add(pair[1]);
pair[1] = pair[1].rotate_left(r) ^ pair[0];
}
// Convert the block to native endianness and xor into the hash state.
state[0] ^= u64::from_le(block[0]);
state[1] ^= u64::from_le(block[1]);
@ -145,9 +139,16 @@ fn mix(state: &mut [u64], block: &[u64]) {
];
// Do the mixing.
for (rot_1, rot_2) in ROTATION_TABLE.iter().cycle().take(ROUNDS) {
umix(&mut state[..2], *rot_1);
umix(&mut state[2..], *rot_2);
for &(rot_1, rot_2) in ROTATION_TABLE.iter().cycle().take(ROUNDS) {
// Skein MIX function.
state[0] = state[0].wrapping_add(state[1]);
state[1] = state[1].rotate_left(rot_1) ^ state[0];
// Skein MIX function.
state[2] = state[2].wrapping_add(state[3]);
state[3] = state[3].rotate_left(rot_2) ^ state[2];
// Permute.
state.swap(1, 3);
}
}