miden_crypto/hash/keccak/
mod.rs

1use core::mem::size_of;
2
3use sha3::Digest as Sha3Digest;
4
5use super::{
6    Felt, HasherExt,
7    digest::{DIGEST256_BYTES, Digest256},
8};
9use crate::field::BasedVectorSpace;
10
11#[cfg(test)]
12mod tests;
13
14// RE-EXPORTS
15// ================================================================================================
16
17/// Re-export of the Keccak hasher from Plonky3 for use in the prover config downstream.
18pub use p3_keccak::{Keccak256Hash, KeccakF, VECTOR_LEN};
19
20// KECCAK256 DIGEST
21// ================================================================================================
22
23/// Keccak-256 digest (32 bytes).
24///
25/// This is a type alias to the generic `Digest256` type.
26pub type Keccak256Digest = Digest256;
27
28// KECCAK256 HASHER
29// ================================================================================================
30
31/// Keccak256 hash function
32#[derive(Debug, Copy, Clone, Eq, PartialEq)]
33pub struct Keccak256;
34
35impl HasherExt for Keccak256 {
36    type Digest = Keccak256Digest;
37
38    fn hash_iter<'a>(slices: impl Iterator<Item = &'a [u8]>) -> Self::Digest {
39        let mut hasher = sha3::Keccak256::new();
40        for slice in slices {
41            hasher.update(slice);
42        }
43        Keccak256Digest::from(<[u8; DIGEST256_BYTES]>::from(hasher.finalize()))
44    }
45}
46
47impl Keccak256 {
48    /// Keccak256 collision resistance is 128-bits for 32-bytes output.
49    pub const COLLISION_RESISTANCE: u32 = 128;
50
51    pub fn hash(bytes: &[u8]) -> Keccak256Digest {
52        let mut hasher = sha3::Keccak256::new();
53        hasher.update(bytes);
54        Keccak256Digest::from(<[u8; DIGEST256_BYTES]>::from(hasher.finalize()))
55    }
56
57    pub fn merge(values: &[Keccak256Digest; 2]) -> Keccak256Digest {
58        Self::hash(Keccak256Digest::digests_as_bytes(values))
59    }
60
61    pub fn merge_many(values: &[Keccak256Digest]) -> Keccak256Digest {
62        let data = Keccak256Digest::digests_as_bytes(values);
63        let mut hasher = sha3::Keccak256::new();
64        hasher.update(data);
65        Keccak256Digest::from(<[u8; DIGEST256_BYTES]>::from(hasher.finalize()))
66    }
67
68    /// Returns a hash of the provided field elements.
69    #[inline(always)]
70    pub fn hash_elements<E>(elements: &[E]) -> Keccak256Digest
71    where
72        E: BasedVectorSpace<Felt>,
73    {
74        hash_elements(elements).into()
75    }
76
77    /// Hashes an iterator of byte slices.
78    #[inline(always)]
79    pub fn hash_iter<'a>(slices: impl Iterator<Item = &'a [u8]>) -> Keccak256Digest {
80        <Self as HasherExt>::hash_iter(slices)
81    }
82}
83
84// HELPER FUNCTIONS
85// ================================================================================================
86
87/// Hash the elements into bytes.
88fn hash_elements<E>(elements: &[E]) -> [u8; DIGEST256_BYTES]
89where
90    E: BasedVectorSpace<Felt>,
91{
92    // don't leak assumptions from felt and check its actual implementation.
93    let digest = {
94        const FELT_BYTES: usize = size_of::<u64>();
95        const { assert!(FELT_BYTES == 8, "buffer arithmetic assumes 8-byte field elements") };
96
97        let mut hasher = sha3::Keccak256::new();
98        // Keccak256 rate: 1600 bits (state) - 512 bits (capacity) = 1088 bits = 136 bytes
99        let mut buf = [0_u8; 136];
100        let mut buf_offset = 0;
101
102        for elem in elements.iter() {
103            for &felt in E::as_basis_coefficients_slice(elem) {
104                buf[buf_offset..buf_offset + FELT_BYTES]
105                    .copy_from_slice(&felt.as_canonical_u64().to_le_bytes());
106                buf_offset += FELT_BYTES;
107
108                if buf_offset == 136 {
109                    hasher.update(buf);
110                    buf_offset = 0;
111                }
112            }
113        }
114
115        if buf_offset > 0 {
116            hasher.update(&buf[..buf_offset]);
117        }
118
119        hasher.finalize()
120    };
121    digest.into()
122}
miden_crypto/hash/keccak/mod.rs

miden_crypto/hash/keccak/
mod.rs
