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comparison src/mac/omac/omac_init.c @ 192:9cc34777b479 libtomcrypt

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propagate from branch 'au.asn.ucc.matt.ltc-orig' (head 9ba8f01f44320e9cb9f19881105ae84f84a43ea9) to branch 'au.asn.ucc.matt.dropbear.ltc' (head dbf51c569bc34956ad948e4cc87a0eeb2170b768)
author Matt Johnston <matt@ucc.asn.au>
date Sun, 08 May 2005 06:36:47 +0000
parents 1c15b283127b
children 39d5d58461d6
comparison
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164:cd1143579f00 192:9cc34777b479
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 #include "tomcrypt.h"
12
13 /**
14 @file omac_init.c
15 OMAC1 support, initialize state, by Tom St Denis
16 */
17
18
19 #ifdef OMAC
20
21 /**
22 Initialize an OMAC state
23 @param omac The OMAC state to initialize
24 @param cipher The index of the desired cipher
25 @param key The secret key
26 @param keylen The length of the secret key (octets)
27 @return CRYPT_OK if successful
28 */
29 int omac_init(omac_state *omac, int cipher, const unsigned char *key, unsigned long keylen)
30 {
31 int err, x, y, mask, msb, len;
32
33 LTC_ARGCHK(omac != NULL);
34 LTC_ARGCHK(key != NULL);
35
36 /* schedule the key */
37 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
38 return err;
39 }
40
41 #ifdef LTC_FAST
42 if (16 % sizeof(LTC_FAST_TYPE)) {
43 return CRYPT_INVALID_ARG;
44 }
45 #endif
46
47 /* now setup the system */
48 switch (cipher_descriptor[cipher].block_length) {
49 case 8: mask = 0x1B;
50 len = 8;
51 break;
52 case 16: mask = 0x87;
53 len = 16;
54 break;
55 default: return CRYPT_INVALID_ARG;
56 }
57
58 if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &omac->key)) != CRYPT_OK) {
59 return err;
60 }
61
62 /* ok now we need Lu and Lu^2 [calc one from the other] */
63
64 /* first calc L which is Ek(0) */
65 zeromem(omac->Lu[0], cipher_descriptor[cipher].block_length);
66 cipher_descriptor[cipher].ecb_encrypt(omac->Lu[0], omac->Lu[0], &omac->key);
67
68 /* now do the mults, whoopy! */
69 for (x = 0; x < 2; x++) {
70 /* if msb(L * u^(x+1)) = 0 then just shift, otherwise shift and xor constant mask */
71 msb = omac->Lu[x][0] >> 7;
72
73 /* shift left */
74 for (y = 0; y < (len - 1); y++) {
75 omac->Lu[x][y] = ((omac->Lu[x][y] << 1) | (omac->Lu[x][y+1] >> 7)) & 255;
76 }
77 omac->Lu[x][len - 1] = ((omac->Lu[x][len - 1] << 1) ^ (msb ? mask : 0)) & 255;
78
79 /* copy up as require */
80 if (x == 0) {
81 XMEMCPY(omac->Lu[1], omac->Lu[0], sizeof(omac->Lu[0]));
82 }
83 }
84
85 /* setup state */
86 omac->cipher_idx = cipher;
87 omac->buflen = 0;
88 omac->blklen = len;
89 zeromem(omac->prev, sizeof(omac->prev));
90 zeromem(omac->block, sizeof(omac->block));
91
92 return CRYPT_OK;
93 }
94
95 #endif