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comparison src/pk/pkcs1/pkcs_1_v15_es_encode.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
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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 pkcs_1_v15_es_encode.c
15 v1.5 Encryption Padding for PKCS #1, Tom St Denis
16 */
17
18 #ifdef PKCS_1
19
20 /**
21 PKCS #1 v1.5 Encryption Padding
22 @param msg The data to encode
23 @param msglen The length of the data (octets)
24 @param modulus_bitlen The bit length of the RSA modulus
25 @param prng An active PRNG
26 @param prng_idx The index of the PRNG desired
27 @param out [out] The destination of the padding
28 @param outlen [in/out] The max size and resulting size of the padding
29 @return CRYPT_OK if successful
30 */
31 int pkcs_1_v15_es_encode(const unsigned char *msg, unsigned long msglen,
32 unsigned long modulus_bitlen,
33 prng_state *prng, int prng_idx,
34 unsigned char *out, unsigned long *outlen)
35 {
36 unsigned long modulus_bytelen, x, y;
37
38 LTC_ARGCHK(msg != NULL);
39 LTC_ARGCHK(out != NULL);
40 LTC_ARGCHK(outlen != NULL);
41
42 /* get modulus len */
43 modulus_bytelen = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
44 if (modulus_bytelen < 12) {
45 return CRYPT_INVALID_ARG;
46 }
47
48 /* verify length */
49 if (msglen > (modulus_bytelen - 11) || *outlen < modulus_bytelen) {
50 return CRYPT_PK_INVALID_SIZE;
51 }
52
53 /* 0x00 0x02 PS 0x00 M */
54 x = 0;
55 out[x++] = 0x00;
56 out[x++] = 0x02;
57 y = modulus_bytelen - msglen - 3;
58 if (prng_descriptor[prng_idx].read(out+x, y, prng) != y) {
59 return CRYPT_ERROR_READPRNG;
60 }
61 x += y;
62 out[x++] = 0x00;
63 XMEMCPY(out+x, msg, msglen);
64 *outlen = modulus_bytelen;
65
66 return CRYPT_OK;
67 }
68
69 #endif /* PKCS_1 */