spongefish/
keccak.rs

1//! **Warning**: this function is not SHA3.
2//! Despite internally we use the same permutation function,
3//! we build a duplex sponge in overwrite mode
4//! on the top of it using the `DuplexSponge` trait.
5use zeroize::{Zeroize, ZeroizeOnDrop};
6
7use crate::duplex_sponge::{DuplexSponge, Permutation};
8
9/// A duplex sponge based on the permutation [`keccak::f1600`]
10/// using [`DuplexSponge`].
11pub type Keccak = DuplexSponge<AlignedKeccakF1600>;
12
13fn transmute_state(st: &mut AlignedKeccakF1600) -> &mut [u64; 25] {
14    unsafe { &mut *std::ptr::from_mut::<AlignedKeccakF1600>(st).cast::<[u64; 25]>() }
15}
16
17/// This is a wrapper around 200-byte buffer that's always 8-byte aligned
18/// to make pointers to it safely convertible to pointers to [u64; 25]
19/// (since u64 words must be 8-byte aligned)
20#[derive(Clone, Zeroize, ZeroizeOnDrop)]
21#[repr(align(8))]
22pub struct AlignedKeccakF1600([u8; 200]);
23
24impl Permutation for AlignedKeccakF1600 {
25    type U = u8;
26    const N: usize = 136 + 64;
27    const R: usize = 136;
28
29    fn new(tag: [u8; 32]) -> Self {
30        let mut state = Self::default();
31        state.0[Self::R..Self::R + 32].copy_from_slice(&tag);
32        state
33    }
34
35    fn permute(&mut self) {
36        keccak::f1600(transmute_state(self));
37    }
38}
39
40impl Default for AlignedKeccakF1600 {
41    fn default() -> Self {
42        Self([0u8; Self::N])
43    }
44}
45
46impl AsRef<[u8]> for AlignedKeccakF1600 {
47    fn as_ref(&self) -> &[u8] {
48        &self.0
49    }
50}
51
52impl AsMut<[u8]> for AlignedKeccakF1600 {
53    fn as_mut(&mut self) -> &mut [u8] {
54        &mut self.0
55    }
56}
spongefish/keccak.rs

spongefish/
keccak.rs
