217cede02ea2d294f1b0cbac483e006144f669b9
3 * $Id: dsa-verify.c,v 1.1 1999/11/19 19:28:00 mdw Exp $
5 * DSA signature verification
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
14 * Catacomb is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU Library General Public License as
16 * published by the Free Software Foundation; either version 2 of the
17 * License, or (at your option) any later version.
19 * Catacomb is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU Library General Public License for more details.
24 * You should have received a copy of the GNU Library General Public
25 * License along with Catacomb; if not, write to the Free
26 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
30 /*----- Revision history --------------------------------------------------*
32 * $Log: dsa-verify.c,v $
33 * Revision 1.1 1999/11/19 19:28:00 mdw
34 * Implementation of the Digital Signature Algorithm.
38 /*----- Header files ------------------------------------------------------*/
44 /*----- Main code ---------------------------------------------------------*/
46 /* --- @dsa_vrfy@ --- *
48 * Arguments: @const dsa_param *dp@ = pointer to DSA parameters
49 * @const mp *y@ = public verification key
50 * @const mp *m@ = message which was signed
51 * @const mp *r, *s@ = the signature
53 * Returns: Zero if the signature is a forgery, nonzero if it's valid.
55 * Use: Verifies a DSA digital signature.
58 #define SHOW(x) do { fputs(#x " = ", stdout); mp_writefile(x, stdout, 16); fputc('\n', stdout); } while (0)
60 int dsa_vrfy(const dsa_param
*dp
, const mp
*y
,
61 const mp
*m
, const mp
*r
, const mp
*s
)
68 /* --- Ensure that all of the signature bits are in range --- */
70 if ((r
->f
| s
->f
) & MP_NEG
)
72 if (MP_CMP(r
, >=, dp
->q
) || MP_CMP(s
, >=, dp
->q
))
75 /* --- Set up Montgomery contexts --- */
77 mpmont_create(&pm
, dp
->p
);
78 mpmont_create(&qm
, dp
->q
);
80 /* --- Compute %$w = s^{-1} \bmod q$% --- */
84 mp_gcd(0, 0, &z
, dp
->q
, (mp
*)s
);
85 w
= mpmont_mul(&qm
, MP_NEW
, z
, qm
.r2
);
89 /* --- Compute %$wr%$ and %$wm$% --- */
91 f
[0].exp
= mpmont_mul(&qm
, MP_NEW
, w
, m
);
92 f
[1].exp
= mpmont_mul(&qm
, MP_NEW
, w
, r
);
96 /* --- Do the exponentiation and take residue mod @q@ --- */
100 w
= mpmont_mexp(&pm
, f
, 2);
101 mp_div(0, &w
, w
, dp
->q
);
102 ok
= MP_CMP(w
, ==, r
);
104 /* --- Tidy up --- */
113 /* --- @dsa_verify@ --- *
115 * Arguments: @const dsa_param *dp@ = pointer to DSA parameters
116 * @const mp *y@ = public verification key
117 * @const void *m@ = pointer to message block
118 * @size_t msz@ = size of message block
119 * @const void *r@ = pointer to @r@ signature half
120 * @size_t rsz@ = size of @r@
121 * @const void *s@ = pointer to @s@ signature half
122 * @size_t ssz@ = size of @s@
124 * Returns: Zero if the signature is a forgery, nonzero if it's valid.
126 * Use: Verifies a DSA digital signature.
129 int dsa_verify(const dsa_param
*dp
, const mp
*y
,
130 const void *m
, size_t msz
,
131 const void *r
, size_t rsz
,
132 const void *s
, size_t ssz
)
134 mp
*mm
= mp_loadb(MP_NEW
, m
, msz
);
135 mp
*rm
= mp_loadb(MP_NEW
, r
, rsz
);
136 mp
*sm
= mp_loadb(MP_NEW
, s
, ssz
);
137 int ok
= dsa_vrfy(dp
, y
, mm
, rm
, sm
);
144 /*----- Test rig ----------------------------------------------------------*/
148 #include <mLib/testrig.h>
152 static int verify(int good
, dstr
*v
)
157 octet hash
[SHA_HASHSZ
];
161 dp
.q
= *(mp
**)v
[0].buf
;
162 dp
.p
= *(mp
**)v
[1].buf
;
163 dp
.g
= *(mp
**)v
[2].buf
;
164 y
= *(mp
**)v
[3].buf
;
167 sha_hash(&c
, v
[4].buf
, v
[4].len
);
170 rc
= dsa_verify(&dp
, y
, hash
, sizeof(hash
),
171 v
[5].buf
, v
[5].len
, v
[6].buf
, v
[6].len
);
175 fputs("\n*** verification failed", stderr
);
177 fputs("\n*** verification succeeded", stderr
);
178 fputs("\nq = ", stderr
); mp_writefile(dp
.q
, stderr
, 16);
179 fputs("\np = ", stderr
); mp_writefile(dp
.p
, stderr
, 16);
180 fputs("\ng = ", stderr
); mp_writefile(dp
.g
, stderr
, 16);
181 fputs("\ny = ", stderr
); mp_writefile(y
, stderr
, 16);
182 fprintf(stderr
, "\nmessage = `%s'", v
[4].buf
);
183 fputs("\nr = ", stderr
); type_hex
.dump(&v
[5], stderr
);
184 fputs("\ns = ", stderr
); type_hex
.dump(&v
[6], stderr
);
196 static int vgood(dstr
*v
) { return verify(1, v
); }
197 static int vbad(dstr
*v
) { return verify(0, v
); }
199 static test_chunk tests
[] = {
200 { "verify-good", vgood
,
201 { &type_mp
, &type_mp
, &type_mp
, &type_mp
,
202 &type_string
, &type_hex
, &type_hex
, 0 } },
203 { "verify-bad", vbad
,
204 { &type_mp
, &type_mp
, &type_mp
, &type_mp
,
205 &type_string
, &type_hex
, &type_hex
, 0 } },
209 int main(int argc
, char *argv
[])
212 test_run(argc
, argv
, tests
, SRCDIR
"/tests/dsa");
218 /*----- That's all, folks -------------------------------------------------*/