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1 | /* -*-c-*- |
2 | * |
ef5f4810 |
3 | * $Id: dsa-gen.c,v 1.3 1999/12/10 23:18:38 mdw Exp $ |
8b810a45 |
4 | * |
5 | * Generate DSA shared parameters |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
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. |
18 | * |
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. |
23 | * |
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, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: dsa-gen.c,v $ |
ef5f4810 |
33 | * Revision 1.3 1999/12/10 23:18:38 mdw |
34 | * Change interface for suggested destinations. |
35 | * |
987bb691 |
36 | * Revision 1.2 1999/11/20 22:23:48 mdw |
37 | * Allow event handler to abort the search process. |
38 | * |
8b810a45 |
39 | * Revision 1.1 1999/11/19 19:28:00 mdw |
40 | * Implementation of the Digital Signature Algorithm. |
41 | * |
42 | */ |
43 | |
44 | /*----- Header files ------------------------------------------------------*/ |
45 | |
46 | #include <stdio.h> |
47 | #include <stdlib.h> |
48 | |
49 | #include "dsa.h" |
ef5f4810 |
50 | #include "fibrand.h" |
8b810a45 |
51 | #include "mp.h" |
ef5f4810 |
52 | #include "mprand.h" |
8b810a45 |
53 | #include "pgen.h" |
54 | #include "rabin.h" |
8b810a45 |
55 | #include "sha.h" |
56 | |
57 | /*----- Main code ---------------------------------------------------------*/ |
58 | |
59 | /* --- @dsa_seed@ --- * |
60 | * |
61 | * Arguments: @dsa_param *dp@ = where to store parameters |
62 | * @unsigned l@ = bitlength of @p@ in bits |
63 | * @const void *k@ = pointer to key material |
8b810a45 |
64 | * @size_t sz@ = size of key material |
ef5f4810 |
65 | * @int (*proc)(int ev, mp *m, void *p)@ = event procedure |
8b810a45 |
66 | * |
67 | * Returns: Zero if all went well, nonzero if key material was |
68 | * unsuitable (one of the @DSAEV@ codes). |
69 | * |
70 | * Use: Generates the DSA shared parameters from a given seed value. |
71 | * This can take quite a long time. The size of @p@ in bits is |
72 | * %$l = 512 + 64l'$%. The DSA standard, FIPS 186, only allows |
73 | * %$0 \le l' \le 8$%. This implementation has no such limit, |
74 | * although @l@ must be a multiple of 8. |
75 | * |
76 | * The event procedure is informed of various happenings during |
77 | * generation. It is passed an event code describing what |
78 | * happened, and a multiprecision number which pertains to the |
987bb691 |
79 | * event code. It may abort the search at any time by returning |
80 | * a nonzero value, which is returned as the result of the |
81 | * function. |
8b810a45 |
82 | */ |
83 | |
84 | int dsa_seed(dsa_param *dp, unsigned l, const void *k, size_t sz, |
987bb691 |
85 | int (*proc)(int /*ev*/, mp */*m*/, void */*p*/), void *arg) |
8b810a45 |
86 | { |
87 | mp *q, *p, *g; |
88 | mp *s = mp_loadb(MP_NEW, k, sz); |
89 | octet *sbuf = xmalloc(sz); |
ef5f4810 |
90 | grand *gr; |
987bb691 |
91 | int fail = 0; |
8b810a45 |
92 | |
93 | l /= 8; |
ef5f4810 |
94 | gr = fibrand_create(LOAD32(k)); |
8b810a45 |
95 | |
96 | /* --- Generate @q@ --- */ |
97 | |
98 | { |
99 | octet xbuf[SHA_HASHSZ], ybuf[SHA_HASHSZ]; |
100 | sha_ctx c; |
101 | int i; |
102 | |
103 | sha_init(&c); |
104 | sha_hash(&c, k, sz); |
105 | sha_done(&c, xbuf); |
106 | |
987bb691 |
107 | mpx_uaddn(s->v, s->vl, 1); |
8b810a45 |
108 | mp_storeb(s, sbuf, sz); |
109 | sha_init(&c); |
110 | sha_hash(&c, sbuf, sz); |
111 | sha_done(&c, ybuf); |
112 | |
113 | for (i = 0; i < sizeof(xbuf); i++) |
114 | xbuf[i] ^= ybuf[i]; |
115 | xbuf[0] |= 0x80; |
116 | xbuf[SHA_HASHSZ - 1] |= 0x01; |
117 | q = mp_loadb(MP_NEW, xbuf, sizeof(xbuf)); |
118 | } |
119 | |
120 | /* --- Quick primality check --- */ |
121 | |
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122 | if (proc && (fail = proc(DSAEV_FINDQ, 0, arg)) != 0) |
123 | goto fail_0; |
124 | |
8b810a45 |
125 | { |
126 | pgen pg; |
127 | int rc = pgen_create(&pg, q); |
128 | pgen_destroy(&pg); |
129 | if (rc == PGEN_COMPOSITE) { |
130 | if (proc) |
987bb691 |
131 | fail = proc(DSAEV_FAILQ, q, arg); |
132 | if (!fail) |
133 | fail = DSAEV_FAILQ; |
8b810a45 |
134 | goto fail_0; |
135 | } |
136 | } |
137 | |
138 | /* --- Ensure that @q@ is prime --- * |
139 | * |
140 | * This requires 18 iterations, because the DSA spec is paranoid. |
141 | * Fortunately, it doesn't actually take very long. |
142 | */ |
143 | |
144 | { |
145 | rabin r; |
146 | int i; |
147 | mp *g = MP_NEW; |
8b810a45 |
148 | |
149 | rabin_create(&r, q); |
150 | for (i = 0; i < 18; i++) { |
ef5f4810 |
151 | g = mprand(g, 8 * SHA_HASHSZ, gr, 1); |
8b810a45 |
152 | if (rabin_test(&r, g) == PGEN_COMPOSITE) |
153 | break; |
987bb691 |
154 | if (proc && (fail = proc(DSAEV_PASSQ, q, arg)) != 0) |
155 | break; |
8b810a45 |
156 | } |
157 | mp_drop(g); |
158 | rabin_destroy(&r); |
987bb691 |
159 | if (fail) |
160 | goto fail_0; |
8b810a45 |
161 | if (i < 18) { |
162 | if (proc) |
987bb691 |
163 | fail = proc(DSAEV_FAILQ, q, arg); |
ef5f4810 |
164 | if (!fail) |
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165 | fail = DSAEV_FAILQ; |
8b810a45 |
166 | goto fail_0; |
167 | } |
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168 | if (proc && (fail = proc(DSAEV_GOODQ, q, arg)) != 0) |
169 | goto fail_0; |
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170 | if (proc && (fail = proc(DSAEV_FINDP, 0, arg)) != 0) |
171 | goto fail_0; |
8b810a45 |
172 | } |
173 | |
174 | /* --- Now generate @p@ --- * |
175 | * |
176 | * This is, unfortunately, rather more messy and complicated. |
177 | */ |
178 | |
179 | { |
180 | mp *q2 = mp_lsl(MP_NEW, q, 1); |
181 | mp *ll = mp_lsl(MP_NEW, MP_ONE, l * 8 - 1); |
182 | unsigned n = l / SHA_HASHSZ, b = l % SHA_HASHSZ; |
183 | size_t psz = SHA_HASHSZ * (n + 1); |
184 | octet *pbuf = xmalloc(psz); |
185 | sha_ctx c; |
186 | unsigned i, j; |
187 | |
188 | /* --- Fiddle with the leftover bytes count --- */ |
189 | |
190 | b = SHA_HASHSZ - b; |
191 | |
192 | /* --- Go round 4096 times trying different @p@ values --- */ |
193 | |
194 | p = MP_NEW; |
195 | for (j = 0; j < 4096; j++) { |
196 | |
197 | /* --- Build a prospective value of @p@ --- */ |
198 | |
199 | { |
200 | octet *pp = pbuf + SHA_HASHSZ * n; |
201 | |
202 | for (i = 0; i <= n; i++) { |
987bb691 |
203 | mpx_uaddn(s->v, s->vl, 1); |
8b810a45 |
204 | mp_storeb(s, sbuf, sz); |
205 | sha_init(&c); |
206 | sha_hash(&c, sbuf, sz); |
207 | sha_done(&c, pp); |
208 | pp -= SHA_HASHSZ; |
209 | } |
210 | |
211 | pbuf[b] &= 0x7f; |
212 | p = mp_loadb(p, pbuf + b, psz - b); |
213 | p = mp_add(p, p, ll); |
214 | } |
215 | |
216 | /* --- Adjust @p@ so that %$p \bmod 2q = 1$% --- */ |
217 | |
218 | { |
219 | mp *c = MP_NEW; |
220 | mp_div(0, &c, p, q2); |
221 | c = mp_sub(c, c, MP_ONE); |
222 | p = mp_sub(p, p, c); |
223 | mp_drop(c); |
224 | } |
225 | |
226 | /* --- Check that @p@ is large enough --- */ |
227 | |
228 | if (MP_CMP(p, <, ll)) |
229 | continue; |
230 | |
231 | /* --- Run a simple primality test --- */ |
232 | |
233 | { |
234 | pgen pg; |
235 | int rc = pgen_create(&pg, p); |
236 | pgen_destroy(&pg); |
237 | if (rc == PGEN_COMPOSITE) |
238 | continue; |
239 | } |
240 | |
241 | /* --- Run the Rabin-Miller test --- */ |
242 | |
243 | { |
244 | rabin r; |
245 | mp *g = MP_NEW; |
246 | |
8b810a45 |
247 | rabin_create(&r, p); |
987bb691 |
248 | if (proc && (fail = proc(DSAEV_TRYP, p, arg)) != 0) |
249 | break; |
8b810a45 |
250 | for (i = 0; i < 5; i++) { |
ef5f4810 |
251 | g = mprand(g, 8 * (psz - b), gr, 1); |
8b810a45 |
252 | if (rabin_test(&r, g) == PGEN_COMPOSITE) |
253 | break; |
987bb691 |
254 | if (proc && (fail = proc(DSAEV_PASSP, p, arg)) != 0) |
255 | break; |
8b810a45 |
256 | } |
257 | mp_drop(g); |
258 | rabin_destroy(&r); |
987bb691 |
259 | if (fail) |
260 | break; |
8b810a45 |
261 | if (i < 5) { |
987bb691 |
262 | if (proc && (fail = proc(DSAEV_FAILP, p, arg)) != 0) |
263 | break; |
8b810a45 |
264 | continue; |
265 | } |
266 | } |
267 | |
268 | /* --- It worked! --- */ |
269 | |
270 | if (proc) |
987bb691 |
271 | fail = proc(DSAEV_GOODP, p, arg); |
ef5f4810 |
272 | if (proc && !fail) |
273 | fail = proc(DSAEV_FINDG, 0, arg); |
8b810a45 |
274 | break; |
275 | } |
276 | |
277 | free(pbuf); |
278 | mp_drop(q2); |
279 | mp_drop(ll); |
987bb691 |
280 | if (j >= 4096 || fail) |
8b810a45 |
281 | goto fail_1; |
282 | } |
283 | |
284 | /* --- Choose a generator of an order-%$q$% subgroup of %$Z^*_p$% --- */ |
285 | |
286 | { |
287 | mp *pp = MP_NEW; |
288 | mpw hw; |
289 | mp h; |
290 | unsigned i; |
291 | mpmont mm; |
292 | |
293 | /* --- Calculate %$p' = (p - 1)/q$% --- */ |
294 | |
ef5f4810 |
295 | pp = mp_sub(MP_NEW, p, MP_ONE); |
296 | mp_div(&pp, 0, pp, q); |
8b810a45 |
297 | |
298 | /* --- Now find %$h$% where %$g = h^{p'} \bmod p \ne 1$% --- */ |
299 | |
300 | mp_build(&h, &hw, &hw + 1); |
301 | mpmont_create(&mm, p); |
302 | for (i = 0; i < NPRIME; i++) { |
303 | hw = ptab[i]; |
987bb691 |
304 | if (proc && (fail = proc(DSAEV_TRYH, &h, arg)) != 0) |
305 | break; |
ef5f4810 |
306 | g = mpmont_exp(&mm, MP_NEW, &h, pp); |
8b810a45 |
307 | if (MP_CMP(g, !=, MP_ONE)) |
308 | break; |
8b810a45 |
309 | mp_drop(g); |
987bb691 |
310 | if (proc && (fail = proc(DSAEV_FAILH, &h, arg)) != 0) |
311 | break; |
8b810a45 |
312 | } |
313 | mp_drop(pp); |
ef5f4810 |
314 | mpmont_destroy(&mm); |
987bb691 |
315 | if (fail) |
316 | goto fail_1; |
8b810a45 |
317 | if (i >= NPRIME) { |
318 | fail = DSAEV_FAILH; |
319 | goto fail_1; |
320 | } |
321 | } |
987bb691 |
322 | if (proc && (fail = proc(DSAEV_GOODG, g, arg) != 0)) |
323 | goto fail_2; |
8b810a45 |
324 | |
325 | /* --- Return the important information that I succeeded --- */ |
326 | |
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327 | dp->g = g; |
8b810a45 |
328 | dp->p = p; |
329 | dp->q = q; |
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330 | mp_drop(s); |
8b810a45 |
331 | free(sbuf); |
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332 | gr->ops->destroy(gr); |
8b810a45 |
333 | return (0); |
334 | |
335 | /* --- Tidy up after failure --- */ |
336 | |
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337 | fail_2: |
338 | mp_drop(g); |
8b810a45 |
339 | fail_1: |
340 | mp_drop(p); |
341 | fail_0: |
342 | mp_drop(q); |
343 | mp_drop(s); |
344 | free(sbuf); |
ef5f4810 |
345 | gr->ops->destroy(gr); |
8b810a45 |
346 | return (-1); |
347 | } |
348 | |
349 | /*----- Test rig ----------------------------------------------------------*/ |
350 | |
351 | #ifdef TEST_RIG |
352 | |
353 | static char baton[] = "/-\\|"; |
354 | static char *b = baton; |
355 | |
987bb691 |
356 | static int event(int ev, mp *m, void *p) |
8b810a45 |
357 | { |
358 | if (ev == DSAEV_TRYP || ev == DSAEV_PASSP) { |
359 | fputc(*b++, stdout); |
360 | fputc('\b', stdout); |
361 | fflush(stdout); |
362 | if (!*b) |
363 | b = baton; |
364 | } |
987bb691 |
365 | return (0); |
8b810a45 |
366 | } |
367 | |
368 | static int verify(dstr *v) |
369 | { |
370 | mp *q = *(mp **)v[2].buf; |
371 | mp *p = *(mp **)v[3].buf; |
372 | mp *g = *(mp **)v[4].buf; |
373 | dsa_param dp; |
374 | unsigned l = *(unsigned *)v[1].buf; |
375 | int ok = 1; |
376 | int rc; |
377 | |
378 | rc = dsa_seed(&dp, l, v[0].buf, v[0].len, event, 0); |
379 | if (rc || MP_CMP(q, !=, dp.q) || |
380 | MP_CMP(p, !=, dp.p) || MP_CMP(g, !=, dp.g)) { |
381 | fputs("\n*** gen failed", stderr); |
382 | fputs("\nseed = ", stderr); type_hex.dump(&v[0], stderr); |
383 | fprintf(stderr, "\nl = %u", l); |
384 | fputs("\n q = ", stderr); mp_writefile(q, stderr, 16); |
385 | fputs("\n p = ", stderr); mp_writefile(q, stderr, 16); |
386 | fputs("\n g = ", stderr); mp_writefile(g, stderr, 16); |
387 | if (!rc) { |
388 | fputs("\ndp.q = ", stderr); mp_writefile(dp.q, stderr, 16); |
389 | fputs("\ndp.p = ", stderr); mp_writefile(dp.p, stderr, 16); |
390 | fputs("\ndp.g = ", stderr); mp_writefile(dp.g, stderr, 16); |
391 | } |
392 | fputc('\n', stderr); |
393 | ok = 0; |
394 | } |
395 | |
396 | mp_drop(q); mp_drop(p); mp_drop(g); |
397 | if (!rc) { |
398 | mp_drop(dp.q); mp_drop(dp.p); mp_drop(dp.g); |
399 | } |
ef5f4810 |
400 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
8b810a45 |
401 | return (ok); |
402 | } |
403 | |
404 | static test_chunk tests[] = { |
405 | { "gen", verify, |
406 | { &type_hex, &type_int, &type_mp, &type_mp, &type_mp, 0 } }, |
407 | { 0, 0, { 0 } } |
408 | }; |
409 | |
410 | int main(int argc, char *argv[]) |
411 | { |
412 | sub_init(); |
413 | test_run(argc, argv, tests, SRCDIR "/tests/dsa"); |
414 | return (0); |
415 | } |
416 | |
417 | #endif |
418 | |
419 | /*----- That's all, folks -------------------------------------------------*/ |