AkurAI-Framework / crates/crypto/src/sha256.rs

Latest change 3aae9f4e85241bcb775c31f5c03094becd3da56a - Pure-Rust UI layer: akurai-ui, akurai-crypto, Tailwind-grade akurai-css by Ólafur Búi Ólafsson

//! SHA-256 (FIPS 180-4).

pub(crate) const BLOCK_LEN: usize = 64;

const H0: [u32; 8] = [
    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19,
];

const K: [u32; 64] = [
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

/// Hash `data` in one call.
pub fn sha256(data: &[u8]) -> [u8; 32] {
    let mut h = Sha256::new();
    h.update(data);
    h.finalize()
}

/// Incremental SHA-256: feed data with [`update`](Self::update), then
/// [`finalize`](Self::finalize).
#[derive(Clone)]
pub struct Sha256 {
    state: [u32; 8],
    buf: [u8; BLOCK_LEN],
    buf_len: usize,
    total_len: u64,
}

impl Default for Sha256 {
    fn default() -> Self {
        Self::new()
    }
}

impl Sha256 {
    /// A fresh hasher.
    pub fn new() -> Self {
        Self {
            state: H0,
            buf: [0; BLOCK_LEN],
            buf_len: 0,
            total_len: 0,
        }
    }

    /// Absorb more input.
    pub fn update(&mut self, mut data: &[u8]) {
        self.total_len = self.total_len.wrapping_add(data.len() as u64);
        if self.buf_len > 0 {
            let take = (BLOCK_LEN - self.buf_len).min(data.len());
            self.buf[self.buf_len..self.buf_len + take].copy_from_slice(&data[..take]);
            self.buf_len += take;
            data = &data[take..];
            if self.buf_len < BLOCK_LEN {
                return;
            }
            compress(&mut self.state, &self.buf);
            self.buf_len = 0;
        }
        let (blocks, rest) = data.as_chunks::<BLOCK_LEN>();
        for block in blocks {
            compress(&mut self.state, block);
        }
        self.buf[..rest.len()].copy_from_slice(rest);
        self.buf_len = rest.len();
    }

    /// Pad, process the final block(s) and return the digest.
    pub fn finalize(mut self) -> [u8; 32] {
        let bit_len = self.total_len.wrapping_mul(8);
        let zeros = (BLOCK_LEN + BLOCK_LEN - 9 - self.buf_len) % BLOCK_LEN;
        let mut padding = [0u8; BLOCK_LEN + 8];
        padding[0] = 0x80;
        padding[1 + zeros..9 + zeros].copy_from_slice(&bit_len.to_be_bytes());
        self.update(&padding[..9 + zeros]);
        digest_bytes(&self.state)
    }
}

fn digest_bytes(state: &[u32; 8]) -> [u8; 32] {
    let mut out = [0u8; 32];
    for (chunk, word) in out.as_chunks_mut::<4>().0.iter_mut().zip(state) {
        chunk.copy_from_slice(&word.to_be_bytes());
    }
    out
}

fn message_schedule(block: &[u8; BLOCK_LEN]) -> [u32; 64] {
    let mut w = [0u32; 64];
    for (word, bytes) in w.iter_mut().zip(block.as_chunks::<4>().0) {
        *word = u32::from_be_bytes(*bytes);
    }
    for i in 16..64 {
        let s0 = w[i - 15].rotate_right(7) ^ w[i - 15].rotate_right(18) ^ (w[i - 15] >> 3);
        let s1 = w[i - 2].rotate_right(17) ^ w[i - 2].rotate_right(19) ^ (w[i - 2] >> 10);
        w[i] = w[i - 16]
            .wrapping_add(s0)
            .wrapping_add(w[i - 7])
            .wrapping_add(s1);
    }
    w
}

fn compress(state: &mut [u32; 8], block: &[u8; BLOCK_LEN]) {
    let w = message_schedule(block);
    let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = *state;
    for i in 0..64 {
        let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
        let ch = (e & f) ^ (!e & g);
        let t1 = h
            .wrapping_add(s1)
            .wrapping_add(ch)
            .wrapping_add(K[i])
            .wrapping_add(w[i]);
        let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
        let maj = (a & b) ^ (a & c) ^ (b & c);
        let t2 = s0.wrapping_add(maj);
        h = g;
        g = f;
        f = e;
        e = d.wrapping_add(t1);
        d = c;
        c = b;
        b = a;
        a = t1.wrapping_add(t2);
    }
    for (s, v) in state.iter_mut().zip([a, b, c, d, e, f, g, h]) {
        *s = s.wrapping_add(v);
    }
}