Mercurial > dropbear

comparison libtomcrypt/src/pk/katja/katja_decrypt_key.c @ 382:0cbe8f6dbf9e

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 2af22fb4e878750b88f80f90d439b316d229796f) to branch 'au.asn.ucc.matt.dropbear' (head 02c413252c90e9de8e03d91e9939dde3029f5c0a)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 02:41:05 +0000
parents
children f849a5ca2efc
comparison
equal deleted inserted replaced
379:b66a00272a90 382:0cbe8f6dbf9e
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 $ */