include/crypto/chacha.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Common values and helper functions for the ChaCha and XChaCha stream ciphers.
   4  *
   5  * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
   6  * security.  Here they share the same key size, tfm context, and setkey
   7  * function; only their IV size and encrypt/decrypt function differ.
   8  *
   9  * The ChaCha paper specifies 20, 12, and 8-round variants.  In general, it is
  10  * recommended to use the 20-round variant ChaCha20.  However, the other
  11  * variants can be needed in some performance-sensitive scenarios.  The generic
  12  * ChaCha code currently allows only the 20 and 12-round variants.
  13  */
  14
  15 #ifndef _CRYPTO_CHACHA_H
  16 #define _CRYPTO_CHACHA_H
  17
  18 #include <crypto/skcipher.h>
  19 #include <linux/types.h>
  20 #include <linux/crypto.h>
  21
  22 /* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
  23 #define CHACHA_IV_SIZE          16
  24
  25 #define CHACHA_KEY_SIZE         32
  26 #define CHACHA_BLOCK_SIZE       64
  27 #define CHACHAPOLY_IV_SIZE      12
  28
  29 /* 192-bit nonce, then 64-bit stream position */
  30 #define XCHACHA_IV_SIZE         32
  31
  32 struct chacha_ctx {
  33         u32 key[8];
  34         int nrounds;
  35 };
  36
  37 void chacha_block(u32 *state, u8 *stream, int nrounds);
  38 static inline void chacha20_block(u32 *state, u8 *stream)
  39 {
  40         chacha_block(state, stream, 20);
  41 }
  42 void hchacha_block(const u32 *in, u32 *out, int nrounds);
  43
  44 void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv);
  45
  46 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
  47                            unsigned int keysize);
  48 int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
  49                            unsigned int keysize);
  50
  51 int crypto_chacha_crypt(struct skcipher_request *req);
  52 int crypto_xchacha_crypt(struct skcipher_request *req);
  53
  54 #endif /* _CRYPTO_CHACHA_H */