Crate fast_chacha

FastChaCha20: High-performance ChaCha20 stream cipher implementation with optional assembly optimizations.

This module provides a ChaCha20 implementation that can use optimized assembly routines if available, and falls back to a pure Rust implementation otherwise. It exposes a simple API for encryption and decryption using the ChaCha20 stream cipher, suitable for cryptographic applications.

Examples

Basic usage with a 32-byte key and 12-byte nonce:

use fast_chacha::FastChaCha20;

let key = [0u8; 32];
let nonce = [0u8; 12];
let mut data = b"plaintext data to encrypt".to_vec();

let mut cipher = FastChaCha20::new(&key, &nonce);
cipher.apply_keystream(&mut data);
// `data` now contains the encrypted bytes

// To decrypt, reinitialize with the same key/nonce and apply again:
let mut cipher = FastChaCha20::new(&key, &nonce);
cipher.apply_keystream(&mut data);
// `data` is now the original plaintext

To use the pure Rust fallback implementation explicitly:

use fast_chacha::FastChaCha20;

let key = [0u8; 32];
let nonce = [0u8; 12];
let mut data = b"some data".to_vec();
let mut cipher = FastChaCha20::new(&key, &nonce);
cipher.apply_keystream_pure(&mut data, 10); // 10 double rounds
// `data` is now encrypted using the pure Rust implementation

Modules

fallback_chacha20

Fallback ChaCha20 Implementation (Pure Rust)

Structs

FastChaCha20

FastChaCha20: Main struct representing a ChaCha20 cipher instance.

Functions

ChaCha20_ctr32_c^⚠

C-compatible ChaCha20 function, used as a fallback or as the main implementation if assembly is not available.

init_cpu_caps

Re-export all public items from the x86 module for x86/x86_64 architectures. Initializes CPU feature detection and populates OPENSSL_ia32cap_P.

is_asm_available

Checks if the assembly-optimized implementation is available at runtime.