linux/include/crypto/chacha.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Common values and helper functions for the ChaCha and XChaCha stream ciphers.
 *
 * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
 * security.  Here they share the same key size, tfm context, and setkey
 * function; only their IV size and encrypt/decrypt function differ.
 *
 * The ChaCha paper specifies 20, 12, and 8-round variants.  In general, it is
 * recommended to use the 20-round variant ChaCha20.  However, the other
 * variants can be needed in some performance-sensitive scenarios.  The generic
 * ChaCha code currently allows only the 20 and 12-round variants.
 */

#ifndef _CRYPTO_CHACHA_H
#define _CRYPTO_CHACHA_H

#include <asm/unaligned.h>
#include <linux/types.h>

/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
#define CHACHA_IV_SIZE …

#define CHACHA_KEY_SIZE …
#define CHACHA_BLOCK_SIZE …
#define CHACHAPOLY_IV_SIZE …

#define CHACHA_STATE_WORDS …

/* 192-bit nonce, then 64-bit stream position */
#define XCHACHA_IV_SIZE …

void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
static inline void chacha20_block(u32 *state, u8 *stream)
{ … }

void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);

static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
{ … }

enum chacha_constants { … };

static inline void chacha_init_consts(u32 *state)
{ … }

void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
{ … }

static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
{ … }

void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
		       unsigned int bytes, int nrounds);
void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
			  unsigned int bytes, int nrounds);

static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
				unsigned int bytes, int nrounds)
{ … }

static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
				  unsigned int bytes)
{ … }

#endif /* _CRYPTO_CHACHA_H */