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comparison libtomcrypt/src/pk/katja/katja_decrypt_key.c @ 398:59c7938af2bd

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merge of '1250b8af44b62d8f4fe0f8d9fc7e7a1cc34e7e1c' and '7f8670ac3bb975f40967f3979d09d2199b7e90c8'
author Matt Johnston <matt@ucc.asn.au>
date Sat, 03 Feb 2007 08:20:30 +0000
parents 0cbe8f6dbf9e
children f849a5ca2efc
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396:e7c1a77d2921 398:59c7938af2bd
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.com
10 */
11 #include "tomcrypt.h"
12
13 /**
14 @file katja_decrypt_key.c
15 Katja PKCS #1 OAEP Decryption, Tom St Denis
16 */
17
18 #ifdef MKAT
19
20 /**
21 (PKCS #1 v2.0) decrypt then OAEP depad
22 @param in The ciphertext
23 @param inlen The length of the ciphertext (octets)
24 @param out [out] The plaintext
25 @param outlen [in/out] The max size and resulting size of the plaintext (octets)
26 @param lparam The system "lparam" value
27 @param lparamlen The length of the lparam value (octets)
28 @param hash_idx The index of the hash desired
29 @param stat [out] Result of the decryption, 1==valid, 0==invalid
30 @param key The corresponding private Katja key
31 @return CRYPT_OK if succcessul (even if invalid)
32 */
33 int katja_decrypt_key(const unsigned char *in, unsigned long inlen,
34 unsigned char *out, unsigned long *outlen,
35 const unsigned char *lparam, unsigned long lparamlen,
36 int hash_idx, int *stat,
37 katja_key *key)
38 {
39 unsigned long modulus_bitlen, modulus_bytelen, x;
40 int err;
41 unsigned char *tmp;
42
43 LTC_ARGCHK(out != NULL);
44 LTC_ARGCHK(outlen != NULL);
45 LTC_ARGCHK(key != NULL);
46 LTC_ARGCHK(stat != NULL);
47
48 /* default to invalid */
49 *stat = 0;
50
51 /* valid hash ? */
52 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
53 return err;
54 }
55
56 /* get modulus len in bits */
57 modulus_bitlen = mp_count_bits( (key->N));
58
59 /* payload is upto pq, so we know q is 1/3rd the size of N and therefore pq is 2/3th the size */
60 modulus_bitlen = ((modulus_bitlen << 1) / 3);
61
62 /* round down to next byte */
63 modulus_bitlen -= (modulus_bitlen & 7) + 8;
64
65 /* outlen must be at least the size of the modulus */
66 modulus_bytelen = mp_unsigned_bin_size( (key->N));
67 if (modulus_bytelen != inlen) {
68 return CRYPT_INVALID_PACKET;
69 }
70
71 /* allocate ram */
72 tmp = XMALLOC(inlen);
73 if (tmp == NULL) {
74 return CRYPT_MEM;
75 }
76
77 /* rsa decode the packet */
78 x = inlen;
79 if ((err = katja_exptmod(in, inlen, tmp, &x, PK_PRIVATE, key)) != CRYPT_OK) {
80 XFREE(tmp);
81 return err;
82 }
83
84 /* shift right by modulus_bytelen - modulus_bitlen/8 bytes */
85 for (x = 0; x < (modulus_bitlen >> 3); x++) {
86 tmp[x] = tmp[x+(modulus_bytelen-(modulus_bitlen>>3))];
87 }
88
89 /* now OAEP decode the packet */
90 err = pkcs_1_oaep_decode(tmp, x, lparam, lparamlen, modulus_bitlen, hash_idx,
91 out, outlen, stat);
92
93 XFREE(tmp);
94 return err;
95 }
96
97 #endif /* MRSA */
98
99
100
101
102
103 /* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_decrypt_key.c,v $ */
104 /* $Revision: 1.4 $ */
105 /* $Date: 2006/03/31 14:15:35 $ */