rns_crypto/

sha256.rs

use alloc::vec::Vec;

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,
];

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

#[derive(Clone)]
pub struct Sha256 {
    h: [u32; 8],
    buffer: Vec<u8>,
    counter: u64,
}

fn rotr(x: u32, y: u32) -> u32 {
    (x >> y) | (x << (32 - y))
}

impl Sha256 {
    pub fn new() -> Self {
        Sha256 {
            h: H_INIT,
            buffer: Vec::new(),
            counter: 0,
        }
    }

    fn process_block(&mut self, block: &[u8]) {
        let mut w = [0u32; 64];
        for i in 0..16 {
            w[i] = u32::from_be_bytes([
                block[i * 4],
                block[i * 4 + 1],
                block[i * 4 + 2],
                block[i * 4 + 3],
            ]);
        }

        for i in 16..64 {
            let s0 = rotr(w[i - 15], 7) ^ rotr(w[i - 15], 18) ^ (w[i - 15] >> 3);
            let s1 = rotr(w[i - 2], 17) ^ rotr(w[i - 2], 19) ^ (w[i - 2] >> 10);
            w[i] = w[i - 16]
                .wrapping_add(s0)
                .wrapping_add(w[i - 7])
                .wrapping_add(s1);
        }

        let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = self.h;

        for i in 0..64 {
            let s0 = rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22);
            let maj = (a & b) ^ (a & c) ^ (b & c);
            let t2 = s0.wrapping_add(maj);
            let s1 = rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25);
            let ch = (e & f) ^ ((!e) & g);
            let t1 = h
                .wrapping_add(s1)
                .wrapping_add(ch)
                .wrapping_add(K[i])
                .wrapping_add(w[i]);

            h = g;
            g = f;
            f = e;
            e = d.wrapping_add(t1);
            d = c;
            c = b;
            b = a;
            a = t1.wrapping_add(t2);
        }

        self.h[0] = self.h[0].wrapping_add(a);
        self.h[1] = self.h[1].wrapping_add(b);
        self.h[2] = self.h[2].wrapping_add(c);
        self.h[3] = self.h[3].wrapping_add(d);
        self.h[4] = self.h[4].wrapping_add(e);
        self.h[5] = self.h[5].wrapping_add(f);
        self.h[6] = self.h[6].wrapping_add(g);
        self.h[7] = self.h[7].wrapping_add(h);
    }

    pub fn update(&mut self, data: &[u8]) {
        if data.is_empty() {
            return;
        }
        self.buffer.extend_from_slice(data);
        self.counter += data.len() as u64;

        while self.buffer.len() >= 64 {
            let block: Vec<u8> = self.buffer.drain(..64).collect();
            self.process_block(&block);
        }
    }

    pub fn digest(&self) -> [u8; 32] {
        let mut clone = self.clone();
        let mdi = clone.counter & 0x3F;
        let length = (clone.counter << 3).to_be_bytes();

        let padlen = if mdi < 56 { 55 - mdi } else { 119 - mdi };

        let mut padding = Vec::with_capacity(padlen as usize + 9);
        padding.push(0x80);
        for _ in 0..padlen {
            padding.push(0x00);
        }
        padding.extend_from_slice(&length);
        clone.update(&padding);

        let mut result = [0u8; 32];
        for (i, &val) in clone.h.iter().enumerate() {
            result[i * 4..i * 4 + 4].copy_from_slice(&val.to_be_bytes());
        }
        result
    }
}

pub fn sha256(data: &[u8]) -> [u8; 32] {
    let mut hasher = Sha256::new();
    hasher.update(data);
    hasher.digest()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_sha256_empty() {
        let expected = [
            0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14,
            0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24,
            0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c,
            0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55,
        ];
        assert_eq!(sha256(b""), expected);
    }

    #[test]
    fn test_sha256_abc() {
        let expected = [
            0xba, 0x78, 0x16, 0xbf, 0x8f, 0x01, 0xcf, 0xea,
            0x41, 0x41, 0x40, 0xde, 0x5d, 0xae, 0x22, 0x23,
            0xb0, 0x03, 0x61, 0xa3, 0x96, 0x17, 0x7a, 0x9c,
            0xb4, 0x10, 0xff, 0x61, 0xf2, 0x00, 0x15, 0xad,
        ];
        assert_eq!(sha256(b"abc"), expected);
    }

    #[test]
    fn test_sha256_long() {
        // SHA-256 of 1000 'a' bytes
        let data = [b'a'; 1000];
        let result = sha256(&data);
        // Known value: sha256("a" * 1000)
        let expected = [
            0x41, 0xed, 0xec, 0xe4, 0x2d, 0x63, 0xe8, 0xd9,
            0xbf, 0x51, 0x5a, 0x9b, 0xa6, 0x93, 0x2e, 0x1c,
            0x20, 0xcb, 0xc9, 0xf5, 0xa5, 0xd1, 0x34, 0x64,
            0x5a, 0xdb, 0x5d, 0xb1, 0xb9, 0x73, 0x7e, 0xa3,
        ];
        assert_eq!(result, expected);
    }

    #[test]
    fn test_sha256_incremental() {
        let mut hasher = Sha256::new();
        hasher.update(b"ab");
        hasher.update(b"c");
        assert_eq!(hasher.digest(), sha256(b"abc"));
    }
}