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
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
/* 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.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
*/
/**
@file eax_init.c
EAX implementation, initialized EAX state, by Tom St Denis
*/
#include "tomcrypt.h"
#ifdef LTC_EAX_MODE
/**
Initialized an EAX state
@param eax [out] The EAX state to initialize
@param cipher The index of the desired cipher
@param key The secret key
@param keylen The length of the secret key (octets)
@param nonce The use-once nonce for the session
@param noncelen The length of the nonce (octets)
@param header The header for the EAX state
@param headerlen The header length (octets)
@return CRYPT_OK if successful
*/
int eax_init(eax_state *eax, int cipher,
const unsigned char *key, unsigned long keylen,
const unsigned char *nonce, unsigned long noncelen,
const unsigned char *header, unsigned long headerlen)
{
unsigned char *buf;
int err, blklen;
omac_state *omac;
unsigned long len;
LTC_ARGCHK(eax != NULL);
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(nonce != NULL);
if (headerlen > 0) {
LTC_ARGCHK(header != NULL);
}
if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
return err;
}
blklen = cipher_descriptor[cipher].block_length;
/* allocate ram */
buf = XMALLOC(MAXBLOCKSIZE);
omac = XMALLOC(sizeof(*omac));
if (buf == NULL || omac == NULL) {
if (buf != NULL) {
XFREE(buf);
}
if (omac != NULL) {
XFREE(omac);
}
return CRYPT_MEM;
}
/* N = LTC_OMAC_0K(nonce) */
zeromem(buf, MAXBLOCKSIZE);
if ((err = omac_init(omac, cipher, key, keylen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* omac the [0]_n */
if ((err = omac_process(omac, buf, blklen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* omac the nonce */
if ((err = omac_process(omac, nonce, noncelen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* store result */
len = sizeof(eax->N);
if ((err = omac_done(omac, eax->N, &len)) != CRYPT_OK) {
goto LBL_ERR;
}
/* H = LTC_OMAC_1K(header) */
zeromem(buf, MAXBLOCKSIZE);
buf[blklen - 1] = 1;
if ((err = omac_init(&eax->headeromac, cipher, key, keylen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* omac the [1]_n */
if ((err = omac_process(&eax->headeromac, buf, blklen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* omac the header */
if (headerlen != 0) {
if ((err = omac_process(&eax->headeromac, header, headerlen)) != CRYPT_OK) {
goto LBL_ERR;
}
}
/* note we don't finish the headeromac, this allows us to add more header later */
/* setup the CTR mode */
if ((err = ctr_start(cipher, eax->N, key, keylen, 0, CTR_COUNTER_BIG_ENDIAN, &eax->ctr)) != CRYPT_OK) {
goto LBL_ERR;
}
/* setup the LTC_OMAC for the ciphertext */
if ((err = omac_init(&eax->ctomac, cipher, key, keylen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* omac [2]_n */
zeromem(buf, MAXBLOCKSIZE);
buf[blklen-1] = 2;
if ((err = omac_process(&eax->ctomac, buf, blklen)) != CRYPT_OK) {
goto LBL_ERR;
}
err = CRYPT_OK;
LBL_ERR:
#ifdef LTC_CLEAN_STACK
zeromem(buf, MAXBLOCKSIZE);
zeromem(omac, sizeof(*omac));
#endif
XFREE(omac);
XFREE(buf);
return err;
}
#endif
/* $Source$ */
/* $Revision$ */
/* $Date$ */
|
