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Remove ChaChaXCore types #512

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Merged
newpavlov merged 10 commits into from
Jan 30, 2026
Merged

Remove ChaChaXCore types #512

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366509c
Make ChaChaXCore a type alias
dhardy Jan 28, 2026
63f9fdc
Remove type alias ChaChaXCore
dhardy Jan 28, 2026
ce3302e
Doc tweak
dhardy Jan 28, 2026
8b9650e
Make ChaChaXRng core field private
dhardy Jan 28, 2026
e998b15
Add inherent {get,set}_block_pos methods
dhardy Jan 29, 2026
1b7b83f
Let set_block_pos use type u64
dhardy Jan 29, 2026
2999132
Rename U32x2 -> StreamId
dhardy Jan 29, 2026
2e21849
Feature-gate fns {set,get}_block_pos
dhardy Jan 30, 2026
fa46419
Remove CryptoGenerator impl
newpavlov Jan 30, 2026
c5970c4
Remove `CryptoGenerator` import
newpavlov Jan 30, 2026
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2 changes: 1 addition & 1 deletion chacha20/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -136,7 +136,7 @@ pub use chacha::{ChaCha8, ChaCha12, ChaCha20, Key, KeyIvInit};
#[cfg(feature = "rng")]
pub use rand_core;
#[cfg(feature = "rng")]
pub use rng::{ChaCha8Core, ChaCha8Rng, ChaCha12Core, ChaCha12Rng, ChaCha20Core, ChaCha20Rng};
pub use rng::{ChaCha8Rng, ChaCha12Rng, ChaCha20Rng};

#[cfg(feature = "legacy")]
pub use legacy::{ChaCha20Legacy, LegacyNonce};
Expand Down
59 changes: 27 additions & 32 deletions chacha20/src/rng.rs
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Expand Up @@ -195,7 +195,7 @@ impl<R: Rounds, V: Variant> ChaChaCore<R, V> {
}

macro_rules! impl_chacha_rng {
($ChaChaXRng:ident, $ChaChaXCore:ident, $rounds:ident, $abst:ident) => {
($ChaChaXRng:ident, $rounds:ident, $abst:ident) => {
/// A cryptographically secure random number generator that uses the ChaCha algorithm.
///
/// ChaCha is a stream cipher designed by Daniel J. Bernstein[^1], that we use as an RNG. It is
Expand Down Expand Up @@ -225,8 +225,9 @@ macro_rules! impl_chacha_rng {
/// seed seed seed seed
/// counter counter stream_id stream_id
/// ```
/// This implementation uses an output buffer of sixteen `u32` words, and uses
/// [`BlockRng`] to implement the [`Rng`] methods.
/// This implementation uses an output buffer of sixteen `u32` words, using
/// [`rand_core::block::BlockRng`] over [`ChaChaCore`] to implement
/// [`rand_core::Rng`].
///
/// # Example for `ChaCha20Rng`
///
Expand Down Expand Up @@ -267,18 +268,15 @@ macro_rules! impl_chacha_rng {
/// [^2]: [eSTREAM: the ECRYPT Stream Cipher Project](http://www.ecrypt.eu.org/stream/)
pub struct $ChaChaXRng {
/// The ChaChaCore struct
pub core: BlockRng<$ChaChaXCore>,
pub core: BlockRng<ChaChaCore<$rounds, Legacy>>,
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}

/// The ChaCha core random number generator
pub struct $ChaChaXCore(ChaChaCore<$rounds, Legacy>);

impl SeedableRng for $ChaChaXCore {
impl SeedableRng for ChaChaCore<$rounds, Legacy> {
type Seed = Seed;

#[inline]
fn from_seed(seed: Self::Seed) -> Self {
Self(ChaChaCore::<$rounds, Legacy>::new(seed.as_ref(), &[0u8; 8]))
ChaChaCore::<$rounds, Legacy>::new(seed.as_ref(), &[0u8; 8])
}
}
impl SeedableRng for $ChaChaXRng {
Expand All @@ -287,7 +285,7 @@ macro_rules! impl_chacha_rng {
#[inline]
fn from_seed(seed: Self::Seed) -> Self {
Self {
core: BlockRng::new($ChaChaXCore::from_seed(seed.into())),
core: BlockRng::new(ChaChaCore::<$rounds, Legacy>::from_seed(seed.into())),
}
}
}
Expand All @@ -308,12 +306,9 @@ macro_rules! impl_chacha_rng {
Ok(())
}
}
impl CryptoGenerator for $ChaChaXCore {}
impl CryptoGenerator for ChaChaCore<$rounds, Legacy> {}
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@newpavlov newpavlov Jan 28, 2026

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If the field will be private this impl can be removed.

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@dhardy dhardy Jan 28, 2026 •
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The point being that we don't need trait CryptoGenerator at all. The trait is (I believe) only used by ReseedingRng, so lets start with that. (Another PR will be needed to update to the new rand_core soon anyway.)

impl TryCryptoRng for $ChaChaXRng {}

#[cfg(feature = "zeroize")]
impl ZeroizeOnDrop for $ChaChaXCore {}

#[cfg(feature = "zeroize")]
impl ZeroizeOnDrop for $ChaChaXRng {}

Expand All @@ -336,8 +331,8 @@ macro_rules! impl_chacha_rng {
/// byte-offset.
#[inline]
pub fn get_word_pos(&self) -> u128 {
let mut block_counter = (u64::from(self.core.core.0.state[13]) << 32)
| u64::from(self.core.core.0.state[12]);
let mut block_counter = (u64::from(self.core.core.state[13]) << 32)
| u64::from(self.core.core.state[12]);
if self.core.word_offset() != 0 {
block_counter = block_counter.wrapping_sub(BUF_BLOCKS as u64);
}
Expand All @@ -360,8 +355,8 @@ macro_rules! impl_chacha_rng {
let index = (word_offset % BLOCK_WORDS as u128) as usize;
let counter = word_offset / BLOCK_WORDS as u128;
//self.set_block_pos(counter as u64);
self.core.core.0.state[12] = counter as u32;
self.core.core.0.state[13] = (counter >> 32) as u32;
self.core.core.state[12] = counter as u32;
self.core.core.state[13] = (counter >> 32) as u32;
self.core.reset_and_skip(index);
}

Expand All @@ -383,16 +378,16 @@ macro_rules! impl_chacha_rng {
pub fn set_block_pos<B: Into<BlockPos>>(&mut self, block_pos: B) {
self.core.reset_and_skip(0);
let block_pos = block_pos.into().0;
self.core.core.0.state[12] = block_pos[0];
self.core.core.0.state[13] = block_pos[1]
self.core.core.state[12] = block_pos[0];
self.core.core.state[13] = block_pos[1]
}

/// Get the block pos.
#[inline]
#[allow(unused)]
pub fn get_block_pos(&self) -> u64 {
let counter =
self.core.core.0.state[12] as u64 | ((self.core.core.0.state[13] as u64) << 32);
self.core.core.state[12] as u64 | ((self.core.core.state[13] as u64) << 32);
if self.core.word_offset() != 0 {
counter - BUF_BLOCKS as u64 + self.core.word_offset() as u64 / 16
} else {
Expand Down Expand Up @@ -440,15 +435,15 @@ macro_rules! impl_chacha_rng {
#[inline]
pub fn set_stream<S: Into<StreamId>>(&mut self, stream: S) {
let stream: StreamId = stream.into();
self.core.core.0.state[14..].copy_from_slice(&stream.0);
self.core.core.state[14..].copy_from_slice(&stream.0);
self.set_block_pos(0);
}

/// Get the stream number.
#[inline]
pub fn get_stream(&self) -> u64 {
let mut result = [0u8; 8];
for (i, &big) in self.core.core.0.state[14..BLOCK_WORDS as usize]
for (i, &big) in self.core.core.state[14..BLOCK_WORDS as usize]
.iter()
.enumerate()
{
Expand All @@ -465,7 +460,7 @@ macro_rules! impl_chacha_rng {
#[inline]
pub fn get_seed(&self) -> [u8; 32] {
let mut result = [0u8; 32];
for (i, &big) in self.core.core.0.state[4..12].iter().enumerate() {
for (i, &big) in self.core.core.state[4..12].iter().enumerate() {
let index = i * 4;
result[index + 0] = big as u8;
result[index + 1] = (big >> 8) as u8;
Expand All @@ -486,8 +481,8 @@ macro_rules! impl_chacha_rng {

impl Eq for $ChaChaXRng {}

impl From<$ChaChaXCore> for $ChaChaXRng {
fn from(core: $ChaChaXCore) -> Self {
impl From<ChaChaCore<$rounds, Legacy>> for $ChaChaXRng {
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fn from(core: ChaChaCore<$rounds, Legacy>) -> Self {
$ChaChaXRng {
core: BlockRng::new(core),
}
Expand Down Expand Up @@ -529,12 +524,12 @@ macro_rules! impl_chacha_rng {
}
}

impl Generator for $ChaChaXCore {
impl Generator for ChaChaCore<$rounds, Legacy> {
type Output = [u32; BUFFER_SIZE];

#[inline]
fn generate(&mut self, r: &mut Self::Output) {
self.0.generate(r);
self.generate(r);
}

#[cfg(feature = "zeroize")]
Expand All @@ -545,11 +540,11 @@ macro_rules! impl_chacha_rng {
};
}

impl_chacha_rng!(ChaCha8Rng, ChaCha8Core, R8, abst8);
impl_chacha_rng!(ChaCha8Rng, R8, abst8);

impl_chacha_rng!(ChaCha12Rng, ChaCha12Core, R12, abst12);
impl_chacha_rng!(ChaCha12Rng, R12, abst12);

impl_chacha_rng!(ChaCha20Rng, ChaCha20Core, R20, abst20);
impl_chacha_rng!(ChaCha20Rng, R20, abst20);

#[cfg(test)]
pub(crate) mod tests {
Expand Down Expand Up @@ -920,7 +915,7 @@ pub(crate) mod tests {
#[test]
fn test_chacha_word_pos_zero() {
let mut rng = ChaChaRng::from_seed(Default::default());
assert_eq!(rng.core.core.0.state[12], 0);
assert_eq!(rng.core.core.state[12], 0);
assert_eq!(rng.core.word_offset(), 0);
assert_eq!(rng.get_word_pos(), 0);
rng.set_word_pos(0);
Expand Down