stego_rust 0.2.0

Library for image steganography with AES-256-GCM encryption and Argon2id key derivation
Documentation 
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use sha2::{Digest, Sha256};

/// Computes the SHA-256 digest of `data`.
pub fn sha256(data: &[u8]) -> [u8; 32] {
    let mut h = Sha256::new();
    h.update(data);
    h.finalize().into()
}

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

    #[test]
    fn sha256_empty_matches_known_digest() {
        // SHA-256("") = e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
        let expected =
            hex_to_bytes("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");
        assert_eq!(sha256(b""), expected);
    }

    fn hex_to_bytes(s: &str) -> [u8; 32] {
        let mut out = [0u8; 32];
        for (i, chunk) in s.as_bytes().chunks(2).enumerate() {
            let hi = hex_nibble(chunk[0]);
            let lo = hex_nibble(chunk[1]);
            out[i] = (hi << 4) | lo;
        }
        out
    }

    fn hex_nibble(c: u8) -> u8 {
        match c {
            b'0'..=b'9' => c - b'0',
            b'a'..=b'f' => c - b'a' + 10,
            _ => panic!("bad hex char"),
        }
    }
}