1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10 #include "tomcrypt_private.h"
11
12 /**
13 @file lrw_start.c
14 LRW_MODE implementation, start mode, Tom St Denis
15 */
16
17 #ifdef LTC_LRW_MODE
18
19 /**
20 Initialize the LRW context
21 @param cipher The cipher desired, must be a 128-bit block cipher
22 @param IV The index value, must be 128-bits
23 @param key The cipher key
24 @param keylen The length of the cipher key in octets
25 @param tweak The tweak value (second key), must be 128-bits
26 @param num_rounds The number of rounds for the cipher (0 == default)
27 @param lrw [out] The LRW state
28 @return CRYPT_OK on success.
29 */
lrw_start(int cipher,const unsigned char * IV,const unsigned char * key,int keylen,const unsigned char * tweak,int num_rounds,symmetric_LRW * lrw)30 int lrw_start( int cipher,
31 const unsigned char *IV,
32 const unsigned char *key, int keylen,
33 const unsigned char *tweak,
34 int num_rounds,
35 symmetric_LRW *lrw)
36 {
37 int err;
38 #ifdef LTC_LRW_TABLES
39 unsigned char B[16];
40 int x, y, z, t;
41 #endif
42
43 LTC_ARGCHK(IV != NULL);
44 LTC_ARGCHK(key != NULL);
45 LTC_ARGCHK(tweak != NULL);
46 LTC_ARGCHK(lrw != NULL);
47
48 #ifdef LTC_FAST
49 if (16 % sizeof(LTC_FAST_TYPE)) {
50 return CRYPT_INVALID_ARG;
51 }
52 #endif
53
54 /* is cipher valid? */
55 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
56 return err;
57 }
58 if (cipher_descriptor[cipher]->block_length != 16) {
59 return CRYPT_INVALID_CIPHER;
60 }
61
62 /* schedule key */
63 if ((err = cipher_descriptor[cipher]->setup(key, keylen, num_rounds, &lrw->key)) != CRYPT_OK) {
64 return err;
65 }
66 lrw->cipher = cipher;
67
68 /* copy the IV and tweak */
69 XMEMCPY(lrw->tweak, tweak, 16);
70
71 #ifdef LTC_LRW_TABLES
72 /* setup tables */
73 /* generate the first table as it has no shifting (from which we make the other tables) */
74 zeromem(B, 16);
75 for (y = 0; y < 256; y++) {
76 B[0] = y;
77 gcm_gf_mult(tweak, B, &lrw->PC[0][y][0]);
78 }
79
80 /* now generate the rest of the tables based the previous table */
81 for (x = 1; x < 16; x++) {
82 for (y = 0; y < 256; y++) {
83 /* now shift it right by 8 bits */
84 t = lrw->PC[x-1][y][15];
85 for (z = 15; z > 0; z--) {
86 lrw->PC[x][y][z] = lrw->PC[x-1][y][z-1];
87 }
88 lrw->PC[x][y][0] = gcm_shift_table[t<<1];
89 lrw->PC[x][y][1] ^= gcm_shift_table[(t<<1)+1];
90 }
91 }
92 #endif
93
94 /* generate first pad */
95 return lrw_setiv(IV, 16, lrw);
96 }
97
98
99 #endif
100 /* ref: $Format:%D$ */
101 /* git commit: $Format:%H$ */
102 /* commit time: $Format:%ai$ */
103