|
380
|
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 $ */ |
