3 * Generalized version of KCDSA
5 * (c) 2004 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
12 * Catacomb is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
17 * Catacomb is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
22 * You should have received a copy of the GNU Library General Public
23 * License along with Catacomb; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
28 /*----- Header files ------------------------------------------------------*/
34 #include "mpbarrett.h"
37 /*----- Main code ---------------------------------------------------------*/
39 /* --- @gkcdsa_beginhash@ --- *
41 * Arguments: @const gkcdsa *c@ = pointer to the context structure
43 * Returns: A hashing context for you to hash the message.
45 * Use: Initializes a hash function correctly for you to hash a
46 * message. Requires @h@, @g@ and @p@.
49 ghash *gkcdsa_beginhash(const gkcdsa *c)
51 ghash *h = GH_INIT(c->h);
52 mp *v = G_TOINT(c->g, MP_NEW, c->p);
53 size_t sz = c->h->bufsz;
54 void *p = xmalloc(sz);
55 if (/*ouch*/ !v) memset(p, 0, sz);
56 else mp_storeb(v, p, sz);
62 /* --- @gkcdsa_endhash@ --- *
64 * Arguments: @const gkcdsa *c@ = pointer to the context structure
65 * @ghash *h@ = the hashing context
69 * Use: Does any final thing that KCDSA wants to do when hashing a
70 * message. (Actually, there's nothing.) The hashing context
74 void gkcdsa_endhash(const gkcdsa *c, ghash *h) { ; }
78 * Arguments: @group *g@ = abstract group
79 * @const gchash *hc@ = hash class
80 * @ge *w@ = a group element
82 * Returns: A hash context, with the hash of @w@ in it.
85 static ghash *hashge(group *g, const gchash *hc, ge *w)
98 rc = G_TORAW(g, &b, w);
101 GH_HASH(h, BBASE(&b), BLEN(&b));
106 /* --- @gkcdsa_sign@ --- *
108 * Arguments: @const gkcdsa *c@ = my context structure
109 * @gkcdsa_sig *s@ = where to put the signature (initialized)
110 * @const void *m@ = pointer to message hash
111 * @mp *k@ = random exponent for this message or null
115 * Use: Signs a message. Requires @g@, @u@, @h@, and @r@ if @k@ is
116 * null. This is a better idea than inventing @k@ yourself.
119 void gkcdsa_sign(const gkcdsa *c, gkcdsa_sig *s, const void *m, mp *k)
124 size_t hsz = c->h->hashsz;
127 if (k) { MP_COPY(k); goto have_k; }
129 k = dsa_nonce(k, g->r, c->u, m, c->h, c->r);
131 if (MP_ZEROP(k)) goto new_k;
132 G_EXP(g, z, g->g, k);
133 if (!s->r) s->r = xmalloc(hsz);
134 h = hashge(g, c->h, z); GH_DONE(h, s->r);
136 x = mp_loadb(s->s, m, hsz);
137 y = mp_loadb(MP_NEW, s->r, hsz);
139 mp_div(0, &x, x, g->r);
140 x = mp_sub(x, g->r, x);
142 if (MP_CMP(x, >=, g->r)) x = mp_sub(x, x, g->r);
143 x = mp_mul(x, x, c->u); mp_div(0, &x, x, g->r);
145 mp_drop(k); mp_drop(y); GH_DESTROY(h); G_DESTROY(g, z);
148 /* --- @gkcdsa_verify@ --- *
150 * Arguments: @const gkcdsa *c@ = my context structure
151 * @const gkcdsa_sig *s@ = the signature to verify
152 * @const void *m@ = pointer to message hash
154 * Returns: Zero if OK, negative on failure.
156 * Use: Checks a signature on a message, Requires @g@, @p@, @h@.
159 int gkcdsa_verify(const gkcdsa *c, const gkcdsa_sig *s, const void *m)
162 size_t hsz = c->h->hashsz;
163 group_expfactor e[2];
170 if (MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r))
172 x = mp_loadb(MP_NEW, m, hsz); y = mp_loadb(MP_NEW, s->r, hsz);
173 x = mp_xor(x, x, y); mp_div(0, &x, x, g->r);
174 e[0].base = c->p; e[0].exp = s->s;
175 e[1].base = g->g; e[1].exp = x;
176 z = G_CREATE(g); G_MEXP(g, z, e, 2);
177 h = hashge(g, c->h, z); p = GH_DONE(h, 0);
178 if (memcmp(p, s->r, hsz) == 0) rc = 0;
179 mp_drop(x); mp_drop(y); G_DESTROY(g, z); GH_DESTROY(h);
183 /*----- Test rig ----------------------------------------------------------*/
189 static group *getgroup(const char *p) {
190 group *g; qd_parse qd;
191 qd.p = p; qd.e = 0; g = group_parse(&qd);
192 if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; }
194 fprintf(stderr, "bad group string `%.*s|%s': %s\n",
195 (int)(qd.p - p), p, qd.p, qd.e);
201 static ge *getge(group *g, const char *p) {
203 if (group_readstring(g, x, p, 0)) {
204 fprintf(stderr, "bad group element `%s'\n", p);
210 static void showge(group *g, const char *p, ge *x) {
211 fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr);
215 static void showmp(const char *p, mp *x, int r) {
216 fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r);
220 static int tsign(dstr *v)
223 gkcdsa_sig s, ss = GKCDSA_SIG_INIT;
231 c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
232 c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf;
233 s.r = (octet *)v[5].buf; s.s = *(mp **)v[6].buf;
234 DENSURE(&d, c.h->hashsz); d.len = c.h->hashsz; memset(d.buf, 0, d.len);
235 ss.r = (octet *)d.buf;
237 x = mp_modinv(MP_NEW, c.u, c.g->r);
238 c.p = G_CREATE(c.g); G_EXP(c.g, c.p, c.g->g, x);
239 h = gkcdsa_beginhash(&c);
240 GH_HASH(h, v[3].buf, v[3].len);
241 gkcdsa_endhash(&c, h);
242 gkcdsa_sign(&c, &ss, GH_DONE(h, 0), k);
244 if (memcmp(s.r, ss.r, c.h->hashsz) || !MP_EQ(s.s, ss.s)) {
246 fprintf(stderr, "*** sign failed!\n");
247 fprintf(stderr, "*** group: %s\n", v[0].buf);
248 fprintf(stderr, "*** hash: %s\n", c.h->name);
249 showmp("private key", c.u, 16);
250 showge(c.g, "public key", c.p);
251 fprintf(stderr, "*** message: `%s'\n", v[3].buf);
252 fprintf(stderr, "*** computed r = ");
253 type_hex.dump(&d, stderr); putc('\n', stderr);
254 showmp("computed s", ss.s, 16);
255 fprintf(stderr, "*** expected r = ");
256 type_hex.dump(&v[5], stderr); putc('\n', stderr);
257 showmp("expected s", s.s, 16);
261 h = gkcdsa_beginhash(&c);
262 GH_HASH(h, v[3].buf, v[3].len);
265 gkcdsa_sign(&c, &ss, m, 0);
266 if (gkcdsa_verify(&c, &ss, m)) {
268 fprintf(stderr, "*** sign cross-check failed!\n");
269 fprintf(stderr, "*** group: %s\n", v[0].buf);
270 fprintf(stderr, "*** hash: %s\n", c.h->name);
271 showmp("private key", c.u, 16);
272 showge(c.g, "public key", c.p);
273 fprintf(stderr, "*** message: `%s'\n", v[3].buf);
274 fprintf(stderr, "*** computed r = ");
275 type_hex.dump(&d, stderr); putc('\n', stderr);
276 showmp("computed s", ss.s, 16);
279 mp_drop(s.s); mp_drop(x); mp_drop(k); dstr_destroy(&d); mp_drop(ss.s);
280 mp_drop(c.u); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
281 assert(mparena_count(MPARENA_GLOBAL) == 0);
285 static int tverify(dstr *v)
293 c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
294 c.p = getge(c.g, v[2].buf);
295 s.r = (octet *)v[4].buf; s.s = *(mp **)v[5].buf;
296 erc = *(int *)v[6].buf;
298 h = gkcdsa_beginhash(&c);
299 GH_HASH(h, v[3].buf, v[3].len);
300 gkcdsa_endhash(&c, h);
301 rc = gkcdsa_verify(&c, &s, GH_DONE(h, 0));
304 fprintf(stderr, "*** verify failed!\n");
305 fprintf(stderr, "*** group: %s\n", v[0].buf);
306 fprintf(stderr, "*** hash: %s\n", c.h->name);
307 showge(c.g, "public key", c.p);
308 fprintf(stderr, "*** message: `%s'\n", v[3].buf);
309 fprintf(stderr, "*** sig r = ");
310 type_hex.dump(&v[4], stderr); putc('\n', stderr);
311 showmp("sig s", s.s, 16);
312 fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail");
314 mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
316 assert(mparena_count(MPARENA_GLOBAL) == 0);
320 static const test_chunk tests[] = {
321 { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string,
322 &type_mp, &type_hex, &type_mp } },
323 { "verify", tverify, { &type_string, &type_string, &type_string,
324 &type_string, &type_hex, &type_mp, &type_int } },
328 int main(int argc, char *argv[])
331 test_run(argc, argv, tests, SRCDIR "/t/gkcdsa");
337 /*----- That's all, folks -------------------------------------------------*/