1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10
11 #include "tomcrypt_private.h"
12
13 #ifdef LTC_CHACHA20POLY1305_MODE
14
15 /**
16 Set IV + counter data (with RFC7905-magic) to the ChaCha20Poly1305 state and reset the context
17 @param st The ChaCha20Poly1305 state
18 @param iv The IV data to add
19 @param ivlen The length of the IV (must be 12 or 8)
20 @param sequence_number 64bit sequence number which is incorporated into IV as described in RFC7905
21 @return CRYPT_OK on success
22 */
chacha20poly1305_setiv_rfc7905(chacha20poly1305_state * st,const unsigned char * iv,unsigned long ivlen,ulong64 sequence_number)23 int chacha20poly1305_setiv_rfc7905(chacha20poly1305_state *st, const unsigned char *iv, unsigned long ivlen, ulong64 sequence_number)
24 {
25 int i;
26 unsigned char combined_iv[12] = { 0 };
27
28 LTC_ARGCHK(st != NULL);
29 LTC_ARGCHK(iv != NULL);
30 LTC_ARGCHK(ivlen == 12);
31
32 STORE64L(sequence_number, combined_iv + 4);
33 for (i = 0; i < 12; i++) combined_iv[i] = iv[i] ^ combined_iv[i];
34 return chacha20poly1305_setiv(st, combined_iv, 12);
35 }
36
37 #endif
38
39 /* ref: $Format:%D$ */
40 /* git commit: $Format:%H$ */
41 /* commit time: $Format:%ai$ */
42