5 * Generalized version of DSA
7 * (c) 2004 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 /*----- Header files ------------------------------------------------------*/
36 #include "mpbarrett.h"
39 /*----- Main code ---------------------------------------------------------*/
41 /* --- @gdsa_beginhash@ --- *
43 * Arguments: @const gdsa *c@ = pointer to the context structure
45 * Returns: A hashing context for you to hash the message.
47 * Use: Initializes a hash function correctly for you to hash a
48 * message. Requires @h@.
51 ghash
*gdsa_beginhash(const gdsa
*c
) { return (GH_INIT(c
->h
)); }
53 /* --- @gdsa_endhash@ --- *
55 * Arguments: @const gdsa *c@ = pointer to the context structure
56 * @ghash *h@ = the hashing context
60 * Use: Does any final thing that DSA wants to do when hashing a
61 * message. (Actually, there's nothing.) The hashing context
65 void gdsa_endhash(const gdsa
*c
, ghash
*h
) { ; }
67 /* --- @gdsa_sign@ --- *
69 * Arguments: @const gdsa *c@ = my context structure
70 * @gdsa_sig *s@ = where to put the signature (initialized)
71 * @const void *m@ = pointer to message hash
72 * @mp *k@ = random exponent for this message or null
76 * Use: Signs a message. Requires @g@, @u@, @h@, and @r@ if @k@ is
77 * null. This is a better idea than inventing @k@ yourself.
80 void gdsa_sign(const gdsa
*c
, gdsa_sig
*s
, const void *m
, mp
*k
)
83 mp
*mr
= dsa_h2n(MP_NEW
, g
->r
, m
, c
->h
->hashsz
);
85 mp
*sr
= s
->r
, *ss
= s
->s
;
88 if (k
) { MP_COPY(k
); goto have_k
; }
90 k
= mprand_range(k
, g
->r
, c
->r
, 0);
92 if (MP_ZEROP(k
)) goto new_k
;
94 sr
= G_TOINT(g
, sr
, z
); assert(sr
);
95 if (MP_ZEROP(sr
)) goto new_k
;
97 mp_div(0, &sr
, sr
, g
->r
);
98 mpbarrett_create(&b
, g
->r
);
99 ss
= mp_mul(ss
, sr
, c
->u
); ss
= mpbarrett_reduce(&b
, ss
, ss
);
100 ss
= mp_add(ss
, ss
, mr
); mp_div(0, &ss
, ss
, g
->r
);
101 k
= mp_modinv(k
, k
, g
->r
);
102 ss
= mp_mul(ss
, ss
, k
); ss
= mpbarrett_reduce(&b
, ss
, ss
);
103 s
->r
= sr
; s
->s
= ss
;
104 mp_drop(k
); mp_drop(mr
); mpbarrett_destroy(&b
); G_DESTROY(g
, z
);
107 /* --- @gdsa_verify@ --- *
109 * Arguments: @const gdsa *c@ = my context structure
110 * @const gdsa_sig *s@ = the signature to verify
111 * @const void *m@ = pointer to message hash
113 * Returns: Zero if OK, negative on failure.
115 * Use: Checks a signature on a message, Requires @g@, @p@ and @h@.
118 int gdsa_verify(const gdsa
*c
, const gdsa_sig
*s
, const void *m
)
121 group_expfactor e
[2];
127 if (MP_CMP(s
->r
, <, MP_ONE
) || MP_CMP(s
->r
, >=, g
->r
) ||
128 MP_CMP(s
->s
, <, MP_ONE
) || MP_CMP(s
->s
, >=, g
->r
))
130 mpbarrett_create(&b
, g
->r
); h
= mp_modinv(MP_NEW
, s
->s
, g
->r
);
131 e
[0].base
= g
->g
; e
[1].base
= c
->p
;
132 t
= dsa_h2n(MP_NEW
, g
->r
, m
, c
->h
->hashsz
); mp_div(0, &t
, t
, g
->r
);
133 t
= mp_mul(t
, t
, h
); e
[0].exp
= t
= mpbarrett_reduce(&b
, t
, t
);
134 h
= mp_mul(h
, s
->r
, h
); e
[1].exp
= h
= mpbarrett_reduce(&b
, h
, h
);
135 w
= G_CREATE(g
); G_MEXP(g
, w
, e
, 2);
136 t
= G_TOINT(g
, t
, w
); if (!t
) goto done
;
137 mp_div(0, &t
, t
, g
->r
); if (MP_EQ(t
, s
->r
)) rc
= 0;
139 G_DESTROY(g
, w
); mp_drop(t
); mp_drop(h
); mpbarrett_destroy(&b
);
143 /*----- Test rig ----------------------------------------------------------*/
147 static group
*getgroup(const char *p
) {
148 group
*g
; qd_parse qd
;
149 qd
.p
= p
; qd
.e
= 0; g
= group_parse(&qd
);
150 if (g
&& !qd_eofp(&qd
)) { G_DESTROYGROUP(g
); g
= 0; qd
.e
= "junk at eof"; }
151 if (!g
) { fprintf(stderr
, "bad group string `%.*s|%s': %s\n", qd
.p
- p
,
152 p
, qd
.p
, qd
.e
); exit(1); }
156 static ge
*getge(group
*g
, const char *p
) {
158 if (group_readstring(g
, x
, p
, 0)) {
159 fprintf(stderr
, "bad group element `%s'\n", p
);
165 static void showge(group
*g
, const char *p
, ge
*x
) {
166 fprintf(stderr
, "*** %s = ", p
); group_writefile(g
, x
, stderr
);
170 static void showmp(const char *p
, mp
*x
, int r
) {
171 fprintf(stderr
, "*** %s = ", p
); mp_writefile(x
, stderr
, r
);
175 static int tsign(dstr
*v
)
178 gdsa_sig s
, ss
= GDSA_SIG_INIT
;
183 c
.g
= getgroup(v
[0].buf
); c
.h
= ghash_byname(v
[1].buf
);
184 c
.u
= *(mp
**)v
[2].buf
; k
= *(mp
**)v
[4].buf
;
185 s
.r
= *(mp
**)v
[5].buf
; s
.s
= *(mp
**)v
[6].buf
;
187 h
= gdsa_beginhash(&c
);
188 GH_HASH(h
, v
[3].buf
, v
[3].len
);
190 gdsa_sign(&c
, &ss
, GH_DONE(h
, 0), k
);
191 if (!MP_EQ(s
.r
, ss
.r
) || !MP_EQ(s
.s
, ss
.s
)) {
193 fprintf(stderr
, "*** sign failed!\n");
194 fprintf(stderr
, "*** group: %s\n", v
[0].buf
);
195 fprintf(stderr
, "*** hash: %s\n", c
.h
->name
);
196 showmp("private key", c
.u
, 16);
197 fprintf(stderr
, "*** message: `%s'\n", v
[3].buf
);
198 showmp("computed r", ss
.r
, 16); showmp("computed s", ss
.s
, 16);
199 showmp("expected r", s
.r
, 16); showmp("expected s", s
.s
, 16);
201 mp_drop(s
.r
); mp_drop(s
.s
); mp_drop(ss
.r
); mp_drop(ss
.s
);
202 mp_drop(k
); mp_drop(c
.u
); G_DESTROYGROUP(c
.g
); GH_DESTROY(h
);
203 assert(mparena_count(MPARENA_GLOBAL
) == 0);
207 static int tverify(dstr
*v
)
215 c
.g
= getgroup(v
[0].buf
); c
.h
= ghash_byname(v
[1].buf
);
216 c
.p
= getge(c
.g
, v
[2].buf
);
217 s
.r
= *(mp
**)v
[4].buf
; s
.s
= *(mp
**)v
[5].buf
;
218 erc
= *(int *)v
[6].buf
;
220 h
= gdsa_beginhash(&c
);
221 GH_HASH(h
, v
[3].buf
, v
[3].len
);
223 rc
= gdsa_verify(&c
, &s
, GH_DONE(h
, 0));
226 fprintf(stderr
, "*** verify failed!\n");
227 fprintf(stderr
, "*** group: %s\n", v
[0].buf
);
228 fprintf(stderr
, "*** hash: %s\n", c
.h
->name
);
229 showge(c
.g
, "public key", c
.p
);
230 fprintf(stderr
, "*** message: `%s'\n", v
[3].buf
);
231 showmp("sig r", s
.r
, 16); showmp("sig s", s
.s
, 16);
232 fprintf(stderr
, "*** expected %s\n", !erc ?
"pass" : "fail");
234 mp_drop(s
.r
); mp_drop(s
.s
); G_DESTROY(c
.g
, c
.p
); G_DESTROYGROUP(c
.g
);
236 assert(mparena_count(MPARENA_GLOBAL
) == 0);
240 static const test_chunk tests
[] = {
241 { "sign", tsign
, { &type_string
, &type_string
, &type_mp
, &type_string
,
242 &type_mp
, &type_mp
, &type_mp
} },
243 { "verify", tverify
, { &type_string
, &type_string
, &type_string
,
244 &type_string
, &type_mp
, &type_mp
, &type_int
} },
248 int main(int argc
, char *argv
[])
251 test_run(argc
, argv
, tests
, SRCDIR
"/tests/gdsa");
257 /*----- That's all, folks -------------------------------------------------*/