1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3 #include "tomcrypt_private.h"
4
5 /**
6 @file cfb_start.c
7 CFB implementation, start chain, Tom St Denis
8 */
9
10
11 #ifdef LTC_CFB_MODE
12
13 /**
14 Initialize a CFB context
15 @param cipher The index of the cipher desired
16 @param IV The initialization vector
17 @param key The secret key
18 @param keylen The length of the secret key (octets)
19 @param num_rounds Number of rounds in the cipher desired (0 for default)
20 @param cfb The CFB state to initialize
21 @return CRYPT_OK if successful
22 */
cfb_start(int cipher,const unsigned char * IV,const unsigned char * key,int keylen,int num_rounds,symmetric_CFB * cfb)23 int cfb_start(int cipher, const unsigned char *IV, const unsigned char *key,
24 int keylen, int num_rounds, symmetric_CFB *cfb)
25 {
26 int x, err;
27
28 LTC_ARGCHK(IV != NULL);
29 LTC_ARGCHK(key != NULL);
30 LTC_ARGCHK(cfb != NULL);
31
32 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
33 return err;
34 }
35
36
37 /* copy data */
38 cfb->cipher = cipher;
39 cfb->blocklen = cipher_descriptor[cipher]->block_length;
40 for (x = 0; x < cfb->blocklen; x++) {
41 cfb->IV[x] = IV[x];
42 }
43
44 /* init the cipher */
45 if ((err = cipher_descriptor[cipher]->setup(key, keylen, num_rounds, &cfb->key)) != CRYPT_OK) {
46 return err;
47 }
48
49 /* encrypt the IV */
50 cfb->padlen = 0;
51 return cipher_descriptor[cfb->cipher]->ecb_encrypt(cfb->IV, cfb->IV, &cfb->key);
52 }
53
54 #endif
55