Struct ChaCha20 

pub struct ChaCha20 { /* private fields */ }

ChaCha20 stream cipher state (RFC 8439).

Holds the initial state (key + nonce + counter) and the current counter value. Buffers the leftover bytes from the previous keystream block so partial calls to apply_keystream work correctly.

Implementations

impl ChaCha20

pub fn new(key: &[u8; 32], nonce: &[u8; 12], counter: u32) -> Self

Initialise a ChaCha20 cipher with a 32-byte key, a 12-byte nonce, and an initial 32-bit block counter.

Per RFC 8439 §2.4 the AEAD construction starts the cipher at counter = 1 (counter = 0 produces the one-time Poly1305 key). Standalone ChaCha20 users typically start at counter = 0 or 1 – whatever their protocol specifies.

pub fn apply_keystream(&mut self, data: &mut [u8])

XOR the keystream into data in place. Encrypts or decrypts indifferently (the cipher is symmetric).

Handles arbitrary lengths and partial blocks: the cipher remembers leftover keystream bytes between calls, so cipher.apply_keystream(b"hi"); cipher.apply_keystream(b"!") produces the same output as one call with b"hi!".

Trait Implementations

impl Clone for ChaCha20

fn clone(&self) -> ChaCha20

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.