ChaCha20 and XChaCha20

ChaCha20 and XChaCha20 algorithms. More...

Files
file	ocrypto_chacha20.h
	ChaCha20 and XChaCha20 algorithms.

Macros
#define	ocrypto_chacha20_KEY_BYTES   (32)
#define	ocrypto_chacha20_NONCE_BYTES_MAX   (12)

Functions
void	ocrypto_chacha20_encode (uint8_t *c, const uint8_t *m, size_t m_len, const uint8_t *n, size_t n_len, const uint8_t key[(32)], uint32_t count)

Incremental ChaCha20 Encoder
This group of functions can be used to incrementally compute the ChaCha20 encryption or decryption for a given message and key, by segmenting a message into smaller chunks. Use pattern: Encoding/Decoding: ocrypto_chacha20_init(ctx, n, n_len, key, count); ocrypto_chacha20_update(ctx, c, m, m_len); ... ocrypto_chacha20_update(ctx, c, m, m_len);
void	ocrypto_chacha20_init (ocrypto_chacha20_ctx *ctx, const uint8_t *n, size_t n_len, const uint8_t key[(32)], uint32_t count)
void	ocrypto_chacha20_update (ocrypto_chacha20_ctx *ctx, uint8_t *c, const uint8_t *m, size_t m_len)

Detailed Description

ChaCha20 and XChaCha20 algorithms.

ChaCha20 is a stream cipher developed by Daniel J. Bernstein based on the 20-round cipher Salsa20/20.

A 256-bit key is expanded into 2^64 randomly accessible streams, each containing 2^64 randomly accessible 64-byte (512-bit) blocks.

The changes from Salsa20/20 to ChaCha20 are designed to improve diffusion per round, conjecturally increasing resistance to cryptanalysis, while preserving - and often improving - time per round.

XChaCha20 uses a 192-bit nonce instead of ChaCha20's 96-bit nonce.

See also

XChaCha

RFC - ChaCha20 and Poly1305 for IETF Protocols

The ChaCha family of stream ciphers