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More code cleanup of the hash.

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This commit is contained in:
Nathan Vegdahl 2020-02-24 13:31:17 +09:00
parent 4e435732d7
commit 27572c8838
1 changed files with 54 additions and 53 deletions
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43
sub_crates/backend/src/hash.rs
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@ -79,7 +79,11 @@ impl LedHash256 {
}
// Hash the message length, in bits.
mix(&mut self.state[..], &[self.message_length * 8, 0, 0, 0]);
self.buf[..8].copy_from_slice(&(self.message_length * 8).to_le_bytes());
for i in (&mut self.buf[8..]).iter_mut() {
*i = 0;
}
self.mix_buffer_into_state();
// Get the digest as a byte array and return it.
let mut digest = [0u8; BLOCK_SIZE];
@ -90,15 +94,7 @@ impl LedHash256 {
return digest;
}
fn mix_buffer_into_state(&mut self) {
let (a, b, c) = unsafe { self.buf.align_to::<u64>() };
debug_assert!(a.is_empty());
debug_assert!(c.is_empty());
mix(&mut self.state[..], b);
}
}
/// The main mix function. Mixes a block into the hash state.
/// The main mix function. Mixes the buffer into the hash state.
///
/// 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
@ -118,12 +114,16 @@ impl LedHash256 {
/// The permute table, as taken from Skein 1.3 256-bit variant:
/// Indices: 0 1 2 3
/// Become: 0 3 2 1
fn mix(state: &mut [u64], block: &[u64]) {
// 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]);
state[2] ^= u64::from_le(block[2]);
state[3] ^= u64::from_le(block[3]);
fn mix_buffer_into_state(&mut self) {
// Convert the buffer to native endian u64's and xor into the
// hash state.
let (a, b, c) = unsafe { self.buf.align_to::<u64>() };
debug_assert!(a.is_empty());
debug_assert!(c.is_empty());
self.state[0] ^= u64::from_le(b[0]);
self.state[1] ^= u64::from_le(b[1]);
self.state[2] ^= u64::from_le(b[2]);
self.state[3] ^= u64::from_le(b[3]);
// Mixing constants.
const ROUNDS: usize = 9;
@ -141,15 +141,16 @@ fn mix(state: &mut [u64], block: &[u64]) {
// Do the mixing.
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];
self.state[0] = self.state[0].wrapping_add(self.state[1]);
self.state[1] = self.state[1].rotate_left(rot_1) ^ self.state[0];
// Skein MIX function.
state[2] = state[2].wrapping_add(state[3]);
state[3] = state[3].rotate_left(rot_2) ^ state[2];
self.state[2] = self.state[2].wrapping_add(self.state[3]);
self.state[3] = self.state[3].rotate_left(rot_2) ^ self.state[2];
// Permute.
state.swap(1, 3);
self.state.swap(1, 3);
}
}
}