1 /* crypto/dsa/dsa_vrf.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
59 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
69 int DSA_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
74 BN_MONT_CTX *mont=NULL;
77 if ((ctx=BN_CTX_new()) == NULL) goto err;
82 /* Calculate W = inv(S) mod Q
84 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
87 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
89 /* u1 = M * w mod q */
90 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
92 /* u2 = r * w mod q */
93 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
95 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
97 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
98 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
99 dsa->p,ctx)) goto err;
101 mont=(BN_MONT_CTX *)dsa->method_mont_p;
108 /* v = ( g^u1 * y^u2 mod p ) mod q */
109 /* let t1 = g ^ u1 mod p */
110 if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err;
111 /* let t2 = y ^ u2 mod p */
112 if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err;
113 /* let u1 = t1 * t2 mod p */
114 if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn;
117 /* let u1 = u1 mod q */
118 if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err;
121 if (!BN_mod_exp2_mont(&t1,dsa->g,&u1,dsa->pub_key,&u2,dsa->p,ctx,mont))
123 /* BN_copy(&u1,&t1); */
124 /* let u1 = u1 mod q */
125 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
128 /* V is now in u1. If the signature is correct, it will be
130 ret=(BN_ucmp(&u1, sig->r) == 0);
133 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
134 if (ctx != NULL) BN_CTX_free(ctx);
141 /* data has already been hashed (probably with SHA or SHA-1). */
143 * 1: correct signature
144 * 0: incorrect signature
147 int DSA_verify(int type, const unsigned char *dgst, int dgst_len,
148 unsigned char *sigbuf, int siglen, DSA *dsa)
154 if (s == NULL) return(ret);
155 if (d2i_DSA_SIG(&s,&sigbuf,siglen) == NULL) goto err;
156 ret=DSA_do_verify(dgst,dgst_len,s,dsa);