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comparison libtomcrypt/src/pk/dsa/dsa_sign_hash.c @ 389:5ff8218bcee9

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 2af95f00ebd5bb7a28b3817db1218442c935388e) to branch 'au.asn.ucc.matt.dropbear' (head ecd779509ef23a8cdf64888904fc9b31d78aa933)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 03:14:55 +0000
parents 0cbe8f6dbf9e
children f849a5ca2efc
comparison
equal deleted inserted replaced
388:fb54020f78e1 389:5ff8218bcee9
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 dsa_sign_hash.c
15 DSA implementation, sign a hash, Tom St Denis
16 */
17
18 #ifdef MDSA
19
20 /**
21 Sign a hash with DSA
22 @param in The hash to sign
23 @param inlen The length of the hash to sign
24 @param r The "r" integer of the signature (caller must initialize with mp_init() first)
25 @param s The "s" integer of the signature (caller must initialize with mp_init() first)
26 @param prng An active PRNG state
27 @param wprng The index of the PRNG desired
28 @param key A private DSA key
29 @return CRYPT_OK if successful
30 */
31 int dsa_sign_hash_raw(const unsigned char *in, unsigned long inlen,
32 void *r, void *s,
33 prng_state *prng, int wprng, dsa_key *key)
34 {
35 void *k, *kinv, *tmp;
36 unsigned char *buf;
37 int err;
38
39 LTC_ARGCHK(in != NULL);
40 LTC_ARGCHK(r != NULL);
41 LTC_ARGCHK(s != NULL);
42 LTC_ARGCHK(key != NULL);
43
44 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
45 return err;
46 }
47 if (key->type != PK_PRIVATE) {
48 return CRYPT_PK_NOT_PRIVATE;
49 }
50
51 /* check group order size */
52 if (key->qord >= MDSA_MAX_GROUP) {
53 return CRYPT_INVALID_ARG;
54 }
55
56 buf = XMALLOC(MDSA_MAX_GROUP);
57 if (buf == NULL) {
58 return CRYPT_MEM;
59 }
60
61 /* Init our temps */
62 if ((err = mp_init_multi(&k, &kinv, &tmp, NULL)) != CRYPT_OK) { goto ERRBUF; }
63
64 retry:
65
66 do {
67 /* gen random k */
68 if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) {
69 err = CRYPT_ERROR_READPRNG;
70 goto error;
71 }
72
73 /* read k */
74 if ((err = mp_read_unsigned_bin(k, buf, key->qord)) != CRYPT_OK) { goto error; }
75
76 /* k > 1 ? */
77 if (mp_cmp_d(k, 1) != LTC_MP_GT) { goto retry; }
78
79 /* test gcd */
80 if ((err = mp_gcd(k, key->q, tmp)) != CRYPT_OK) { goto error; }
81 } while (mp_cmp_d(tmp, 1) != LTC_MP_EQ);
82
83 /* now find 1/k mod q */
84 if ((err = mp_invmod(k, key->q, kinv)) != CRYPT_OK) { goto error; }
85
86 /* now find r = g^k mod p mod q */
87 if ((err = mp_exptmod(key->g, k, key->p, r)) != CRYPT_OK) { goto error; }
88 if ((err = mp_mod(r, key->q, r)) != CRYPT_OK) { goto error; }
89
90 if (mp_iszero(r) == LTC_MP_YES) { goto retry; }
91
92 /* now find s = (in + xr)/k mod q */
93 if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, inlen)) != CRYPT_OK) { goto error; }
94 if ((err = mp_mul(key->x, r, s)) != CRYPT_OK) { goto error; }
95 if ((err = mp_add(s, tmp, s)) != CRYPT_OK) { goto error; }
96 if ((err = mp_mulmod(s, kinv, key->q, s)) != CRYPT_OK) { goto error; }
97
98 if (mp_iszero(s) == LTC_MP_YES) { goto retry; }
99
100 err = CRYPT_OK;
101 error:
102 mp_clear_multi(k, kinv, tmp, NULL);
103 ERRBUF:
104 #ifdef LTC_CLEAN_STACK
105 zeromem(buf, MDSA_MAX_GROUP);
106 #endif
107 XFREE(buf);
108 return err;
109 }
110
111 /**
112 Sign a hash with DSA
113 @param in The hash to sign
114 @param inlen The length of the hash to sign
115 @param out [out] Where to store the signature
116 @param outlen [in/out] The max size and resulting size of the signature
117 @param prng An active PRNG state
118 @param wprng The index of the PRNG desired
119 @param key A private DSA key
120 @return CRYPT_OK if successful
121 */
122 int dsa_sign_hash(const unsigned char *in, unsigned long inlen,
123 unsigned char *out, unsigned long *outlen,
124 prng_state *prng, int wprng, dsa_key *key)
125 {
126 void *r, *s;
127 int err;
128
129 LTC_ARGCHK(in != NULL);
130 LTC_ARGCHK(out != NULL);
131 LTC_ARGCHK(outlen != NULL);
132 LTC_ARGCHK(key != NULL);
133
134 if (mp_init_multi(&r, &s, NULL) != CRYPT_OK) {
135 return CRYPT_MEM;
136 }
137
138 if ((err = dsa_sign_hash_raw(in, inlen, r, s, prng, wprng, key)) != CRYPT_OK) {
139 goto error;
140 }
141
142 err = der_encode_sequence_multi(out, outlen,
143 LTC_ASN1_INTEGER, 1UL, r,
144 LTC_ASN1_INTEGER, 1UL, s,
145 LTC_ASN1_EOL, 0UL, NULL);
146
147 error:
148 mp_clear_multi(r, s, NULL);
149 return err;
150 }
151
152 #endif
153
154 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_sign_hash.c,v $ */
155 /* $Revision: 1.12 $ */
156 /* $Date: 2006/12/04 22:27:56 $ */