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comparison libtomcrypt/src/encauth/gcm/gcm_process.c @ 399:a707e6148060

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merge of '5fdf69ca60d1683cdd9f4c2595134bed26394834' and '6b61c50f4cf888bea302ac8fcf5dbb573b443251'
author Matt Johnston <matt@ucc.asn.au>
date Sat, 03 Feb 2007 08:20:34 +0000
parents 0cbe8f6dbf9e
children f849a5ca2efc
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394:17d097fc111c 399:a707e6148060
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, [email protected], http://libtomcrypt.com
10 */
11
12 /**
13 @file gcm_process.c
14 GCM implementation, process message data, by Tom St Denis
15 */
16 #include "tomcrypt.h"
17
18 #ifdef GCM_MODE
19
20 /**
21 Process plaintext/ciphertext through GCM
22 @param gcm The GCM state
23 @param pt The plaintext
24 @param ptlen The plaintext length (ciphertext length is the same)
25 @param ct The ciphertext
26 @param direction Encrypt or Decrypt mode (GCM_ENCRYPT or GCM_DECRYPT)
27 @return CRYPT_OK on success
28 */
29 int gcm_process(gcm_state *gcm,
30 unsigned char *pt, unsigned long ptlen,
31 unsigned char *ct,
32 int direction)
33 {
34 unsigned long x;
35 int y, err;
36 unsigned char b;
37
38 LTC_ARGCHK(gcm != NULL);
39 if (ptlen > 0) {
40 LTC_ARGCHK(pt != NULL);
41 LTC_ARGCHK(ct != NULL);
42 }
43
44 if (gcm->buflen > 16 || gcm->buflen < 0) {
45 return CRYPT_INVALID_ARG;
46 }
47
48 if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
49 return err;
50 }
51
52 /* in AAD mode? */
53 if (gcm->mode == GCM_MODE_AAD) {
54 /* let's process the AAD */
55 if (gcm->buflen) {
56 gcm->totlen += gcm->buflen * CONST64(8);
57 gcm_mult_h(gcm, gcm->X);
58 }
59
60 /* increment counter */
61 for (y = 15; y >= 12; y--) {
62 if (++gcm->Y[y] & 255) { break; }
63 }
64 /* encrypt the counter */
65 if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
66 return err;
67 }
68
69 gcm->buflen = 0;
70 gcm->mode = GCM_MODE_TEXT;
71 }
72
73 if (gcm->mode != GCM_MODE_TEXT) {
74 return CRYPT_INVALID_ARG;
75 }
76
77 x = 0;
78 #ifdef LTC_FAST
79 if (gcm->buflen == 0) {
80 if (direction == GCM_ENCRYPT) {
81 for (x = 0; x < (ptlen & ~15); x += 16) {
82 /* ctr encrypt */
83 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
84 *((LTC_FAST_TYPE*)(&ct[x + y])) = *((LTC_FAST_TYPE*)(&pt[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y]));
85 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y]));
86 }
87 /* GMAC it */
88 gcm->pttotlen += 128;
89 gcm_mult_h(gcm, gcm->X);
90 /* increment counter */
91 for (y = 15; y >= 12; y--) {
92 if (++gcm->Y[y] & 255) { break; }
93 }
94 if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
95 return err;
96 }
97 }
98 } else {
99 for (x = 0; x < (ptlen & ~15); x += 16) {
100 /* ctr encrypt */
101 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
102 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y]));
103 *((LTC_FAST_TYPE*)(&pt[x + y])) = *((LTC_FAST_TYPE*)(&ct[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y]));
104 }
105 /* GMAC it */
106 gcm->pttotlen += 128;
107 gcm_mult_h(gcm, gcm->X);
108 /* increment counter */
109 for (y = 15; y >= 12; y--) {
110 if (++gcm->Y[y] & 255) { break; }
111 }
112 if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
113 return err;
114 }
115 }
116 }
117 }
118 #endif
119
120 /* process text */
121 for (; x < ptlen; x++) {
122 if (gcm->buflen == 16) {
123 gcm->pttotlen += 128;
124 gcm_mult_h(gcm, gcm->X);
125
126 /* increment counter */
127 for (y = 15; y >= 12; y--) {
128 if (++gcm->Y[y] & 255) { break; }
129 }
130 if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
131 return err;
132 }
133 gcm->buflen = 0;
134 }
135
136 if (direction == GCM_ENCRYPT) {
137 b = ct[x] = pt[x] ^ gcm->buf[gcm->buflen];
138 } else {
139 b = ct[x];
140 pt[x] = ct[x] ^ gcm->buf[gcm->buflen];
141 }
142 gcm->X[gcm->buflen++] ^= b;
143 }
144
145 return CRYPT_OK;
146 }
147
148 #endif
149
150 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_process.c,v $ */
151 /* $Revision: 1.14 $ */
152 /* $Date: 2006/11/19 19:33:36 $ */