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feat: add chacha counter initialization #51

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feat: add chacha counter initialization #51

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9 changes: 5 additions & 4 deletions src/crypto/chacha.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ pub fn chacha_block<const ROUNDS: u8>(input: [u32; 16]) -> [u32; 16] {
}

/// Initialize the ChaCha internal state, with a 256-bit key and 64-bit nonce.
pub const fn chacha_init(key: [u8; 32], nonce: [u8; 8]) -> [u32; 16] {
pub const fn chacha_init(key: [u8; 32], counter: [u8; 8], nonce: [u8; 8]) -> [u32; 16] {
let mut state = [0u32; 16];
state[0] = chacha_pack(CHACHA_TAU, 0);
state[1] = chacha_pack(CHACHA_TAU, 4);
Expand All @@ -65,8 +65,8 @@ pub const fn chacha_init(key: [u8; 32], nonce: [u8; 8]) -> [u32; 16] {
state[11] = chacha_pack(&key, 28);

// 64-bit counter
state[12] = 0;
state[13] = 0;
state[12] = chacha_pack(&counter, 0);
state[13] = chacha_pack(&counter, 4);
// Nonce
state[14] = chacha_pack(&nonce, 0);
state[15] = chacha_pack(&nonce, 4);
Expand Down Expand Up @@ -95,10 +95,11 @@ mod tests {
macro_rules! ietf_test_vector {
($key_hex: tt, $nonce_hex: tt, $keystream_hex: tt) => {
let key: [u8; 32] = hex::decode($key_hex).unwrap().try_into().unwrap();
let counter = [0u8; 8];
let nonce: [u8; 8] = hex::decode($nonce_hex).unwrap().try_into().unwrap();
let expected_keystream: Vec<u8> = hex::decode($keystream_hex).unwrap();

let mut state = chacha_init(key, nonce);
let mut state = chacha_init(key, counter, nonce);
let mut keystream: Vec<u8> = Vec::with_capacity(expected_keystream.len());

while expected_keystream.len() > keystream.len() {
Expand Down
13 changes: 8 additions & 5 deletions src/rand/chacha.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,16 +31,17 @@ impl<const ROUNDS: u8> ChaCha<ROUNDS> {
pub fn new() -> Self {
let mut key: [u8; 32] = Default::default();
crate::entropy::system(&mut key);
let counter = [0u8; 8];
let mut nonce: [u8; 8] = Default::default();
crate::entropy::system(&mut nonce);
let state = chacha::chacha_init(key, nonce);
let state = chacha::chacha_init(key, counter, nonce);
Self { state }
}

/// Create a new [`ChaCha`] instance, using the provided key and nonce.
#[must_use]
pub const fn new_key(key: [u8; 32], nonce: [u8; 8]) -> Self {
let state = chacha::chacha_init(key, nonce);
pub const fn new_key(key: [u8; 32], counter: [u8; 8], nonce: [u8; 8]) -> Self {
let state = chacha::chacha_init(key, counter, nonce);
Self { state }
}
}
Expand All @@ -50,9 +51,10 @@ impl<const ROUNDS: u8> Default for ChaCha<ROUNDS> {
fn default() -> Self {
let mut key: [u8; 32] = Default::default();
crate::entropy::system(&mut key);
let counter = [0u8; 8];
let mut nonce: [u8; 8] = Default::default();
crate::entropy::system(&mut nonce);
let state = chacha::chacha_init(key, nonce);
let state = chacha::chacha_init(key, counter, nonce);
Self { state }
}
}
Expand Down Expand Up @@ -97,8 +99,9 @@ impl<const ROUNDS: u8> SeedableRng<40, 64> for ChaCha<ROUNDS> {
let mut key = [0_u8; 32];
let mut nonce = [0_u8; 8];
key.copy_from_slice(&seed[..32]);
let counter = [0u8; 8];
nonce.copy_from_slice(&seed[32..]);
self.state = chacha::chacha_init(key, nonce);
self.state = chacha::chacha_init(key, counter, nonce);
}
}

Expand Down