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comparison libtomcrypt/src/pk/katja/katja_exptmod.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_exptmod.c
15 Katja PKCS-style exptmod, Tom St Denis
16 */
17
18 #ifdef MKAT
19
20 /**
21 Compute an RSA modular exponentiation
22 @param in The input data to send into RSA
23 @param inlen The length of the input (octets)
24 @param out [out] The destination
25 @param outlen [in/out] The max size and resulting size of the output
26 @param which Which exponent to use, e.g. PK_PRIVATE or PK_PUBLIC
27 @param key The RSA key to use
28 @return CRYPT_OK if successful
29 */
30 int katja_exptmod(const unsigned char *in, unsigned long inlen,
31 unsigned char *out, unsigned long *outlen, int which,
32 katja_key *key)
33 {
34 void *tmp, *tmpa, *tmpb;
35 unsigned long x;
36 int err;
37
38 LTC_ARGCHK(in != NULL);
39 LTC_ARGCHK(out != NULL);
40 LTC_ARGCHK(outlen != NULL);
41 LTC_ARGCHK(key != NULL);
42
43 /* is the key of the right type for the operation? */
44 if (which == PK_PRIVATE && (key->type != PK_PRIVATE)) {
45 return CRYPT_PK_NOT_PRIVATE;
46 }
47
48 /* must be a private or public operation */
49 if (which != PK_PRIVATE && which != PK_PUBLIC) {
50 return CRYPT_PK_INVALID_TYPE;
51 }
52
53 /* init and copy into tmp */
54 if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != CRYPT_OK) { return err; }
55 if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, (int)inlen)) != CRYPT_OK) { goto error; }
56
57 /* sanity check on the input */
58 if (mp_cmp(key->N, tmp) == LTC_MP_LT) {
59 err = CRYPT_PK_INVALID_SIZE;
60 goto done;
61 }
62
63 /* are we using the private exponent and is the key optimized? */
64 if (which == PK_PRIVATE) {
65 /* tmpa = tmp^dP mod p */
66 if ((err = mp_exptmod(tmp, key->dP, key->p, tmpa)) != CRYPT_OK) { goto error; }
67
68 /* tmpb = tmp^dQ mod q */
69 if ((err = mp_exptmod(tmp, key->dQ, key->q, tmpb)) != CRYPT_OK) { goto error; }
70
71 /* tmp = (tmpa - tmpb) * qInv (mod p) */
72 if ((err = mp_sub(tmpa, tmpb, tmp)) != CRYPT_OK) { goto error; }
73 if ((err = mp_mulmod(tmp, key->qP, key->p, tmp)) != CRYPT_OK) { goto error; }
74
75 /* tmp = tmpb + q * tmp */
76 if ((err = mp_mul(tmp, key->q, tmp)) != CRYPT_OK) { goto error; }
77 if ((err = mp_add(tmp, tmpb, tmp)) != CRYPT_OK) { goto error; }
78 } else {
79 /* exptmod it */
80 if ((err = mp_exptmod(tmp, key->N, key->N, tmp)) != CRYPT_OK) { goto error; }
81 }
82
83 /* read it back */
84 x = (unsigned long)mp_unsigned_bin_size(key->N);
85 if (x > *outlen) {
86 *outlen = x;
87 err = CRYPT_BUFFER_OVERFLOW;
88 goto done;
89 }
90
91 /* this should never happen ... */
92 if (mp_unsigned_bin_size(tmp) > mp_unsigned_bin_size(key->N)) {
93 err = CRYPT_ERROR;
94 goto done;
95 }
96 *outlen = x;
97
98 /* convert it */
99 zeromem(out, x);
100 if ((err = mp_to_unsigned_bin(tmp, out+(x-mp_unsigned_bin_size(tmp)))) != CRYPT_OK) { goto error; }
101
102 /* clean up and return */
103 err = CRYPT_OK;
104 goto done;
105 error:
106 done:
107 mp_clear_multi(tmp, tmpa, tmpb, NULL);
108 return err;
109 }
110
111 #endif
112
113 /* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_exptmod.c,v $ */
114 /* $Revision: 1.5 $ */
115 /* $Date: 2006/06/16 21:53:41 $ */