3 * $Id: dsa-gen.c,v 1.6 2000/07/29 10:00:14 mdw Exp $
5 * Generate DSA shared parameters
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 --------------------------------------------------*
33 * Revision 1.6 2000/07/29 10:00:14 mdw
34 * Rename `dsa_seed' to `dsa_gen' for consistency with other parameter-
35 * generation interfaces.
37 * Revision 1.5 2000/02/12 18:21:02 mdw
38 * Overhaul of key management (again).
40 * Revision 1.4 1999/12/22 15:52:44 mdw
41 * Reworking for new prime-search system.
43 * Revision 1.3 1999/12/10 23:18:38 mdw
44 * Change interface for suggested destinations.
46 * Revision 1.2 1999/11/20 22:23:48 mdw
47 * Allow event handler to abort the search process.
49 * Revision 1.1 1999/11/19 19:28:00 mdw
50 * Implementation of the Digital Signature Algorithm.
54 /*----- Header files ------------------------------------------------------*/
66 #include "primorial.h"
69 /*----- The DSA stepper ---------------------------------------------------*/
73 * Arguments: @pgen_event *ev@ = pointer to event block
74 * @dsa_stepctx *d@ = pointer to stepping context
76 * Returns: A @PGEN@ result code.
78 * Use: Steps the generator once, reads the result, and tests it.
81 static int next(pgen_event *ev, dsa_stepctx *d)
86 /* --- Load the new candidate --- */
88 m = mprand(ev->m, d->bits, d->r, d->or);
90 /* --- Force to be a multiple of @q@ --- */
94 mp_div(0, &r, m, d->q);
101 /* --- Do the trial division --- */
105 mp_gcd(&g, 0, 0, m, primorial);
106 if (MP_CMP(g, ==, MP_ONE) || MP_CMP(g, ==, m))
113 /* --- Return the result --- */
118 /* --- @dsa_step@ --- */
120 int dsa_step(int rq, pgen_event *ev, void *p)
128 return (next(ev, d));
135 /*----- Glue code ---------------------------------------------------------*/
137 /* --- @dsa_gen@ --- *
139 * Arguments: @dsa_param *dp@ = where to store parameters
140 * @unsigned ql@ = length of @q@ in bits
141 * @unsigned pl@ = length of @p@ in bits
142 * @unsigned steps@ = number of steps to find @q@
143 * @const void *k@ = pointer to key material
144 * @size_t sz@ = size of key material
145 * @pgen_proc *event@ = event handler function
146 * @void *ectx@ = argument for event handler
148 * Returns: @PGEN_DONE@ if everything worked ok; @PGEN_ABORT@ otherwise.
150 * Use: Generates the DSA shared parameters from a given seed value.
152 * The parameters are a prime %$q$%, relatively small, and a
153 * large prime %$p = kq + 1$% for some %$k$%, together with a
154 * generator %$g$% of the cyclic subgroup of order %$q$%. These
155 * are actually the same as the Diffie-Hellman parameter set,
156 * but the generation algorithm is different.
158 * The algorithm used is a compatible extension of the method
159 * described in the DSA standard, FIPS 186. The standard
160 * requires that %$q$% be 160 bits in size (i.e., @ql == 160@)
161 * and that the length of %$p$% be %$L = 512 + 64l$% for some
162 * %$l$%. Neither limitation applies to this implementation.
165 int dsa_gen(dsa_param *dp, unsigned ql, unsigned pl, unsigned steps,
166 const void *k, size_t sz, pgen_proc *event, void *ectx)
174 /* --- Initialize the stepping context --- */
176 s.r = dsarand_create(k, sz);
179 /* --- Find @q@ --- */
182 s.r->ops->misc(s.r, DSARAND_PASSES, 2);
184 if ((dp->q = pgen("q", MP_NEW, MP_NEW, event, ectx, steps, dsa_step, &s,
185 rabin_iters(ql), pgen_test, &r)) == 0)
188 /* --- Find @p@ --- */
190 s.q = mp_lsl(MP_NEW, dp->q, 1);
191 s.r->ops->misc(s.r, DSARAND_PASSES, 1);
193 if ((dp->p = pgen("p", MP_NEW, MP_NEW, event, ectx, 4096, dsa_step, &s,
194 rabin_iters(pl), pgen_test, &r)) == 0)
198 /* --- Find @g@ --- *
200 * The division returns remainder 1. This doesn't matter.
203 mpmont_create(&p.mm, dp->p);
204 qc = MP_NEW; mp_div(&qc, 0, dp->p, dp->q);
208 if ((dp->g = pgen("g", MP_NEW, MP_NEW, event, ectx, 0, prim_step, &i,
209 1, prim_test, &p)) == 0)
215 mpmont_destroy(&p.mm);
216 s.r->ops->destroy(s.r);
219 /* --- Tidy up when things go wrong --- */
223 mpmont_destroy(&p.mm);
228 s.r->ops->destroy(s.r);
232 /*----- Test rig ----------------------------------------------------------*/
236 static int verify(dstr *v)
238 mp *q = *(mp **)v[2].buf;
239 mp *p = *(mp **)v[3].buf;
240 mp *g = *(mp **)v[4].buf;
242 unsigned l = *(unsigned *)v[1].buf;
246 rc = dsa_gen(&dp, 160, l, 1, v[0].buf, v[0].len, pgen_evspin, 0);
247 if (rc || MP_CMP(q, !=, dp.q) ||
248 MP_CMP(p, !=, dp.p) || MP_CMP(g, !=, dp.g)) {
249 fputs("\n*** gen failed", stderr);
250 fputs("\nseed = ", stderr); type_hex.dump(&v[0], stderr);
251 fprintf(stderr, "\nl = %u", l);
252 fputs("\n q = ", stderr); mp_writefile(q, stderr, 16);
253 fputs("\n p = ", stderr); mp_writefile(p, stderr, 16);
254 fputs("\n g = ", stderr); mp_writefile(g, stderr, 16);
256 fputs("\ndp.q = ", stderr); mp_writefile(dp.q, stderr, 16);
257 fputs("\ndp.p = ", stderr); mp_writefile(dp.p, stderr, 16);
258 fputs("\ndp.g = ", stderr); mp_writefile(dp.g, stderr, 16);
264 mp_drop(q); mp_drop(p); mp_drop(g);
266 mp_drop(dp.q); mp_drop(dp.p); mp_drop(dp.g);
268 assert(mparena_count(MPARENA_GLOBAL) == 1); /* Primorial! */
272 static test_chunk tests[] = {
274 { &type_hex, &type_int, &type_mp, &type_mp, &type_mp, 0 } },
278 int main(int argc, char *argv[])
281 test_run(argc, argv, tests, SRCDIR "/tests/dsa");
287 /*----- That's all, folks -------------------------------------------------*/