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comparison eax_init.c @ 3:7faae8f46238 libtomcrypt-orig

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Branch renaming
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:25:41 +0000
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children 5d99163f7e32
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-1:000000000000 3:7faae8f46238
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.org
10 */
11
12 /* EAX Implementation by Tom St Denis */
13 #include "mycrypt.h"
14
15 #ifdef EAX_MODE
16
17 int eax_init(eax_state *eax, int cipher, const unsigned char *key, unsigned long keylen,
18 const unsigned char *nonce, unsigned long noncelen,
19 const unsigned char *header, unsigned long headerlen)
20 {
21 unsigned char buf[MAXBLOCKSIZE];
22 int err, blklen;
23 omac_state omac;
24 unsigned long len;
25
26
27 _ARGCHK(eax != NULL);
28 _ARGCHK(key != NULL);
29 _ARGCHK(nonce != NULL);
30 if (headerlen > 0) {
31 _ARGCHK(header != NULL);
32 }
33
34 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
35 return err;
36 }
37 blklen = cipher_descriptor[cipher].block_length;
38
39 /* N = OMAC_0K(nonce) */
40 zeromem(buf, sizeof(buf));
41 if ((err = omac_init(&omac, cipher, key, keylen)) != CRYPT_OK) {
42 return err;
43 }
44
45 /* omac the [0]_n */
46 if ((err = omac_process(&omac, buf, blklen)) != CRYPT_OK) {
47 return err;
48 }
49 /* omac the nonce */
50 if ((err = omac_process(&omac, nonce, noncelen)) != CRYPT_OK) {
51 return err;
52 }
53 /* store result */
54 len = sizeof(eax->N);
55 if ((err = omac_done(&omac, eax->N, &len)) != CRYPT_OK) {
56 return err;
57 }
58
59 /* H = OMAC_1K(header) */
60 zeromem(buf, sizeof(buf));
61 buf[blklen - 1] = 1;
62
63 if ((err = omac_init(&eax->headeromac, cipher, key, keylen)) != CRYPT_OK) {
64 return err;
65 }
66
67 /* omac the [1]_n */
68 if ((err = omac_process(&eax->headeromac, buf, blklen)) != CRYPT_OK) {
69 return err;
70 }
71 /* omac the header */
72 if (headerlen != 0) {
73 if ((err = omac_process(&eax->headeromac, header, headerlen)) != CRYPT_OK) {
74 return err;
75 }
76 }
77
78 /* note we don't finish the headeromac, this allows us to add more header later */
79
80 /* setup the CTR mode */
81 if ((err = ctr_start(cipher, eax->N, key, keylen, 0, &eax->ctr)) != CRYPT_OK) {
82 return err;
83 }
84 /* use big-endian counter */
85 eax->ctr.mode = 1;
86
87 /* setup the OMAC for the ciphertext */
88 if ((err = omac_init(&eax->ctomac, cipher, key, keylen)) != CRYPT_OK) {
89 return err;
90 }
91
92 /* omac [2]_n */
93 zeromem(buf, sizeof(buf));
94 buf[blklen-1] = 2;
95 if ((err = omac_process(&eax->ctomac, buf, blklen)) != CRYPT_OK) {
96 return err;
97 }
98
99 #ifdef CLEAN_STACK
100 zeromem(buf, sizeof(buf));
101 zeromem(&omac, sizeof(omac));
102 #endif
103 return CRYPT_OK;
104 }
105
106 #endif