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comparison ocb_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 /* OCB Implementation by Tom St Denis */
13 #include "mycrypt.h"
14
15 #ifdef OCB_MODE
16
17 static const struct {
18 int len;
19 unsigned char poly_div[MAXBLOCKSIZE],
20 poly_mul[MAXBLOCKSIZE];
21 } polys[] = {
22 {
23 8,
24 { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D },
25 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1B }
26 }, {
27 16,
28 { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
29 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43 },
30 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
31 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 }
32 }
33 };
34
35 int ocb_init(ocb_state *ocb, int cipher,
36 const unsigned char *key, unsigned long keylen, const unsigned char *nonce)
37 {
38 int poly, x, y, m, err;
39
40 _ARGCHK(ocb != NULL);
41 _ARGCHK(key != NULL);
42 _ARGCHK(nonce != NULL);
43
44 /* valid cipher? */
45 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
46 return err;
47 }
48
49 /* determine which polys to use */
50 ocb->block_len = cipher_descriptor[cipher].block_length;
51 for (poly = 0; poly < (int)(sizeof(polys)/sizeof(polys[0])); poly++) {
52 if (polys[poly].len == ocb->block_len) {
53 break;
54 }
55 }
56 if (polys[poly].len != ocb->block_len) {
57 return CRYPT_INVALID_ARG;
58 }
59
60 /* schedule the key */
61 if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ocb->key)) != CRYPT_OK) {
62 return err;
63 }
64
65 /* find L = E[0] */
66 zeromem(ocb->L, ocb->block_len);
67 cipher_descriptor[cipher].ecb_encrypt(ocb->L, ocb->L, &ocb->key);
68
69 /* find R = E[N xor L] */
70 for (x = 0; x < ocb->block_len; x++) {
71 ocb->R[x] = ocb->L[x] ^ nonce[x];
72 }
73 cipher_descriptor[cipher].ecb_encrypt(ocb->R, ocb->R, &ocb->key);
74
75 /* find Ls[i] = L << i for i == 0..31 */
76 memcpy(ocb->Ls[0], ocb->L, ocb->block_len);
77 for (x = 1; x < 32; x++) {
78 m = ocb->Ls[x-1][0] >> 7;
79 for (y = 0; y < ocb->block_len-1; y++) {
80 ocb->Ls[x][y] = ((ocb->Ls[x-1][y] << 1) | (ocb->Ls[x-1][y+1] >> 7)) & 255;
81 }
82 ocb->Ls[x][ocb->block_len-1] = (ocb->Ls[x-1][ocb->block_len-1] << 1) & 255;
83
84 if (m == 1) {
85 for (y = 0; y < ocb->block_len; y++) {
86 ocb->Ls[x][y] ^= polys[poly].poly_mul[y];
87 }
88 }
89 }
90
91 /* find Lr = L / x */
92 m = ocb->L[ocb->block_len-1] & 1;
93
94 /* shift right */
95 for (x = ocb->block_len - 1; x > 0; x--) {
96 ocb->Lr[x] = ((ocb->L[x] >> 1) | (ocb->L[x-1] << 7)) & 255;
97 }
98 ocb->Lr[0] = ocb->L[0] >> 1;
99
100 if (m == 1) {
101 for (x = 0; x < ocb->block_len; x++) {
102 ocb->Lr[x] ^= polys[poly].poly_div[x];
103 }
104 }
105
106 /* set Li, checksum */
107 zeromem(ocb->Li, ocb->block_len);
108 zeromem(ocb->checksum, ocb->block_len);
109
110 /* set other params */
111 ocb->block_index = 1;
112 ocb->cipher = cipher;
113
114 return CRYPT_OK;
115 }
116
117 #endif