Repository navigation
Expand file tree
/
Copy pathcbc_decrypt.c
More file actions
95 lines (82 loc) · 2.61 KB
/
Copy pathcbc_decrypt.c
File metadata and controls
95 lines (82 loc) · 2.61 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
#include "tomcrypt.h"
/**
@file cbc_decrypt.c
CBC implementation, encrypt block, Tom St Denis
*/
#ifdef LTC_CBC_MODE
/**
CBC decrypt
@param ct Ciphertext
@param pt [out] Plaintext
@param len The number of bytes to process (must be multiple of block length)
@param cbc CBC state
@return CRYPT_OK if successful
*/
int cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc)
{
int x, err;
unsigned char tmp[16];
#ifdef LTC_FAST
LTC_FAST_TYPE tmpy;
#else
unsigned char tmpy;
#endif
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(cbc != NULL);
if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
return err;
}
/* is blocklen valid? */
if (cbc->blocklen < 1 || cbc->blocklen > (int)sizeof(cbc->IV) || cbc->blocklen > (int)sizeof(tmp)) {
return CRYPT_INVALID_ARG;
}
if (len % cbc->blocklen) {
return CRYPT_INVALID_ARG;
}
#ifdef LTC_FAST
if (cbc->blocklen % sizeof(LTC_FAST_TYPE)) {
return CRYPT_INVALID_ARG;
}
#endif
if (cipher_descriptor[cbc->cipher].accel_cbc_decrypt != NULL) {
return cipher_descriptor[cbc->cipher].accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key);
} else {
while (len) {
/* decrypt */
if ((err = cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key)) != CRYPT_OK) {
return err;
}
/* xor IV against plaintext */
#if defined(LTC_FAST)
for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) {
tmpy = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) ^ *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)tmp + x));
*(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)ct + x));
*(LTC_FAST_TYPE_PTR_CAST((unsigned char *)pt + x)) = tmpy;
}
#else
for (x = 0; x < cbc->blocklen; x++) {
tmpy = tmp[x] ^ cbc->IV[x];
cbc->IV[x] = ct[x];
pt[x] = tmpy;
}
#endif
ct += cbc->blocklen;
pt += cbc->blocklen;
len -= cbc->blocklen;
}
}
return CRYPT_OK;
}
#endif
/* ref: tag: v1.18.2, master */
/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
/* commit time: 2018-07-01 22:49:01 +0200 */