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comparison src/pk/pkcs1/pkcs_1_oaep_encode.c @ 191:1c15b283127b libtomcrypt-orig

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Import of libtomcrypt 1.02 with manual path rename rearrangement etc
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 13:23:02 +0000
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children 39d5d58461d6
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143:5d99163f7e32 191:1c15b283127b
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 pkcs_1_oaep_encode.c
15 OAEP Padding for PKCS #1, Tom St Denis
16 */
17
18 #ifdef PKCS_1
19
20 /**
21 PKCS #1 v2.00 OAEP encode
22 @param msg The data to encode
23 @param msglen The length of the data to encode (octets)
24 @param lparam A session or system parameter (can be NULL)
25 @param lparamlen The length of the lparam data
26 @param modulus_bitlen The bit length of the RSA modulus
27 @param prng An active PRNG state
28 @param prng_idx The index of the PRNG desired
29 @param hash_idx The index of the hash desired
30 @param out [out] The destination for the encoded data
31 @param outlen [in/out] The max size and resulting size of the encoded data
32 @return CRYPT_OK if successful
33 */
34 int pkcs_1_oaep_encode(const unsigned char *msg, unsigned long msglen,
35 const unsigned char *lparam, unsigned long lparamlen,
36 unsigned long modulus_bitlen, prng_state *prng,
37 int prng_idx, int hash_idx,
38 unsigned char *out, unsigned long *outlen)
39 {
40 unsigned char *DB, *seed, *mask;
41 unsigned long hLen, x, y, modulus_len;
42 int err;
43
44 LTC_ARGCHK(msg != NULL);
45 LTC_ARGCHK(out != NULL);
46 LTC_ARGCHK(outlen != NULL);
47
48 /* test valid hash */
49 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
50 return err;
51 }
52
53 /* valid prng */
54 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
55 return err;
56 }
57
58 hLen = hash_descriptor[hash_idx].hashsize;
59 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
60
61 /* test message size */
62 if ((2*hLen >= (modulus_len - 2)) || (msglen > (modulus_len - 2*hLen - 2))) {
63 return CRYPT_PK_INVALID_SIZE;
64 }
65
66 /* allocate ram for DB/mask/salt of size modulus_len */
67 DB = XMALLOC(modulus_len);
68 mask = XMALLOC(modulus_len);
69 seed = XMALLOC(modulus_len);
70 if (DB == NULL || mask == NULL || seed == NULL) {
71 if (DB != NULL) {
72 XFREE(DB);
73 }
74 if (mask != NULL) {
75 XFREE(mask);
76 }
77 if (seed != NULL) {
78 XFREE(seed);
79 }
80 return CRYPT_MEM;
81 }
82
83 /* get lhash */
84 /* DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */
85 x = modulus_len;
86 if (lparam != NULL) {
87 if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) {
88 goto LBL_ERR;
89 }
90 } else {
91 /* can't pass hash_memory a NULL so use DB with zero length */
92 if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) {
93 goto LBL_ERR;
94 }
95 }
96
97 /* append PS then 0x01 (to lhash) */
98 x = hLen;
99 y = modulus_len - msglen - 2*hLen - 2;
100 while (y--) {
101 DB[x++] = 0x00;
102 }
103 DB[x++] = 0x01;
104
105 /* message */
106 y = msglen;
107 while (y--) {
108 DB[x++] = *msg++;
109 }
110
111 /* now choose a random seed */
112 if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) {
113 err = CRYPT_ERROR_READPRNG;
114 goto LBL_ERR;
115 }
116
117 /* compute MGF1 of seed (k - hlen - 1) */
118 if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
119 goto LBL_ERR;
120 }
121
122 /* xor against DB */
123 for (y = 0; y < (modulus_len - hLen - 1); y++) {
124 DB[y] ^= mask[y];
125 }
126
127 /* compute MGF1 of maskedDB (hLen) */
128 if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) {
129 goto LBL_ERR;
130 }
131
132 /* XOR against seed */
133 for (y = 0; y < hLen; y++) {
134 seed[y] ^= mask[y];
135 }
136
137 /* create string of length modulus_len */
138 if (*outlen < modulus_len) {
139 err = CRYPT_BUFFER_OVERFLOW;
140 goto LBL_ERR;
141 }
142
143 /* start output which is 0x00 || maskedSeed || maskedDB */
144 x = 0;
145 out[x++] = 0x00;
146 for (y = 0; y < hLen; y++) {
147 out[x++] = seed[y];
148 }
149 for (y = 0; y < modulus_len - hLen - 1; y++) {
150 out[x++] = DB[y];
151 }
152 *outlen = x;
153
154 err = CRYPT_OK;
155 LBL_ERR:
156 #ifdef LTC_CLEAN_STACK
157 zeromem(DB, modulus_len);
158 zeromem(seed, modulus_len);
159 zeromem(mask, modulus_len);
160 #endif
161
162 XFREE(seed);
163 XFREE(mask);
164 XFREE(DB);
165
166 return err;
167 }
168
169 #endif /* PKCS_1 */
170