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
28 /* 192-bit nonce, then 64-bit stream position */
29 #define XCHACHA_IV_SIZE 32
30
31 struct chacha_ctx {
32 u32 key[8];
33 int nrounds;
34 };
35
36 void chacha_block(u32 *state, u8 *stream, int nrounds);
chacha20_block(u32 * state,u8 * stream)37 static inline void chacha20_block(u32 *state, u8 *stream)
38 {
39 chacha_block(state, stream, 20);
40 }
41 void hchacha_block(const u32 *in, u32 *out, int nrounds);
42
43 void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv);
44
45 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
46 unsigned int keysize);
47 int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
48 unsigned int keysize);
49
50 int crypto_chacha_crypt(struct skcipher_request *req);
51 int crypto_xchacha_crypt(struct skcipher_request *req);
52
53 #endif /* _CRYPTO_CHACHA_H */
54