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comparison pkcs_1_v15_es_encode.c @ 15:6362d3854bb4 libtomcrypt-orig

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0.96 release of LibTomCrypt
author Matt Johnston <matt@ucc.asn.au>
date Tue, 15 Jun 2004 14:07:21 +0000
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children 5d99163f7e32
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3:7faae8f46238 15:6362d3854bb4
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 "mycrypt.h"
12
13 /* v1.5 Encryption Padding for PKCS #1 -- Tom St Denis */
14
15 #ifdef PKCS_1
16
17 int pkcs_1_v15_es_encode(const unsigned char *msg, unsigned long msglen,
18 unsigned long modulus_bitlen,
19 prng_state *prng, int prng_idx,
20 unsigned char *out, unsigned long *outlen)
21 {
22 unsigned long modulus_bytelen, x, y;
23
24 _ARGCHK(msg != NULL);
25 _ARGCHK(out != NULL);
26 _ARGCHK(outlen != NULL);
27
28 /* get modulus len */
29 modulus_bytelen = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
30 if (modulus_bytelen < 12) {
31 return CRYPT_INVALID_ARG;
32 }
33
34 /* verify length */
35 if (msglen > (modulus_bytelen - 11) || *outlen < modulus_bytelen) {
36 return CRYPT_PK_INVALID_SIZE;
37 }
38
39 /* 0x00 0x02 PS 0x00 M */
40 x = 0;
41 out[x++] = 0x00;
42 out[x++] = 0x02;
43 y = modulus_bytelen - msglen - 3;
44 if (prng_descriptor[prng_idx].read(out+x, y, prng) != y) {
45 return CRYPT_ERROR_READPRNG;
46 }
47 x += y;
48 out[x++] = 0x00;
49 memcpy(out+x, msg, msglen);
50 *outlen = modulus_bytelen;
51
52 return CRYPT_OK;
53 }
54
55 #endif /* PKCS_1 */