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/* 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 <crypto/skcipher.h>
#include <linux/types.h>
#include <linux/crypto.h>
/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
#define CHACHA_IV_SIZE 16
#define CHACHA_KEY_SIZE 32
#define CHACHA_BLOCK_SIZE 64
#define CHACHAPOLY_IV_SIZE 12
/* 192-bit nonce, then 64-bit stream position */
#define XCHACHA_IV_SIZE 32
struct chacha_ctx {
u32 key[8];
int nrounds;
};
void chacha_block(u32 *state, u8 *stream, int nrounds);
static inline void chacha20_block(u32 *state, u8 *stream)
{
chacha_block(state, stream, 20);
}
void hchacha_block(const u32 *in, u32 *out, int nrounds);
void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv);
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize);
int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize);
int crypto_chacha_crypt(struct skcipher_request *req);
int crypto_xchacha_crypt(struct skcipher_request *req);
enum chacha_constants { /* expand 32-byte k */
CHACHA_CONSTANT_EXPA = 0x61707865U,
CHACHA_CONSTANT_ND_3 = 0x3320646eU,
CHACHA_CONSTANT_2_BY = 0x79622d32U,
CHACHA_CONSTANT_TE_K = 0x6b206574U
};
static inline void chacha_init_consts(u32 *state)
{
state[0] = CHACHA_CONSTANT_EXPA;
state[1] = CHACHA_CONSTANT_ND_3;
state[2] = CHACHA_CONSTANT_2_BY;
state[3] = CHACHA_CONSTANT_TE_K;
}
#endif /* _CRYPTO_CHACHA_H */
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