1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11
12 /**
13 @file gcm_add_iv.c
14 GCM implementation, add IV data to the state, by Tom St Denis
15 */
16 #include "tomcrypt.h"
17
18 #ifdef GCM_MODE
19
20 /**
21 Add IV data to the GCM state
22 @param gcm The GCM state
23 @param IV The initial value data to add
24 @param IVlen The length of the IV
25 @return CRYPT_OK on success
26 */
gcm_add_iv(gcm_state * gcm,const unsigned char * IV,unsigned long IVlen)27 int gcm_add_iv(gcm_state *gcm,
28 const unsigned char *IV, unsigned long IVlen)
29 {
30 unsigned long x, y;
31 int err;
32
33 LTC_ARGCHK(gcm != NULL);
34 if (IVlen > 0) {
35 LTC_ARGCHK(IV != NULL);
36 }
37
38 /* must be in IV mode */
39 if (gcm->mode != GCM_MODE_IV) {
40 return CRYPT_INVALID_ARG;
41 }
42
43 if (gcm->buflen >= 16 || gcm->buflen < 0) {
44 return CRYPT_INVALID_ARG;
45 }
46
47 if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
48 return err;
49 }
50
51
52 /* trip the ivmode flag */
53 if (IVlen + gcm->buflen > 12) {
54 gcm->ivmode |= 1;
55 }
56
57 x = 0;
58 #ifdef LTC_FAST
59 if (gcm->buflen == 0) {
60 for (x = 0; x < (IVlen & ~15); x += 16) {
61 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
62 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&IV[x + y]));
63 }
64 gcm_mult_h(gcm, gcm->X);
65 gcm->totlen += 128;
66 }
67 IV += x;
68 }
69 #endif
70
71 /* start adding IV data to the state */
72 for (; x < IVlen; x++) {
73 gcm->buf[gcm->buflen++] = *IV++;
74
75 if (gcm->buflen == 16) {
76 /* GF mult it */
77 for (y = 0; y < 16; y++) {
78 gcm->X[y] ^= gcm->buf[y];
79 }
80 gcm_mult_h(gcm, gcm->X);
81 gcm->buflen = 0;
82 gcm->totlen += 128;
83 }
84 }
85
86 return CRYPT_OK;
87 }
88
89 #endif
90
91
92 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_add_iv.c,v $ */
93 /* $Revision: 1.7 $ */
94 /* $Date: 2006/03/31 14:15:35 $ */
95