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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: dsa-gen.c,v 1.2 1999/11/20 22:23:48 mdw Exp $ |
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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 $ |
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33 | * Revision 1.2 1999/11/20 22:23:48 mdw |
34 | * Allow event handler to abort the search process. |
35 | * |
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36 | * Revision 1.1 1999/11/19 19:28:00 mdw |
37 | * Implementation of the Digital Signature Algorithm. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <stdio.h> |
44 | #include <stdlib.h> |
45 | |
46 | #include "dsa.h" |
47 | #include "mp.h" |
48 | #include "pgen.h" |
49 | #include "rabin.h" |
50 | #include "rc4.h" |
51 | #include "sha.h" |
52 | |
53 | /*----- Main code ---------------------------------------------------------*/ |
54 | |
55 | /* --- @dsa_seed@ --- * |
56 | * |
57 | * Arguments: @dsa_param *dp@ = where to store parameters |
58 | * @unsigned l@ = bitlength of @p@ in bits |
59 | * @const void *k@ = pointer to key material |
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60 | * @int (*proc)(int ev, mp *m, void *p)@ = event procedure |
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61 | * @size_t sz@ = size of key material |
62 | * |
63 | * Returns: Zero if all went well, nonzero if key material was |
64 | * unsuitable (one of the @DSAEV@ codes). |
65 | * |
66 | * Use: Generates the DSA shared parameters from a given seed value. |
67 | * This can take quite a long time. The size of @p@ in bits is |
68 | * %$l = 512 + 64l'$%. The DSA standard, FIPS 186, only allows |
69 | * %$0 \le l' \le 8$%. This implementation has no such limit, |
70 | * although @l@ must be a multiple of 8. |
71 | * |
72 | * The event procedure is informed of various happenings during |
73 | * generation. It is passed an event code describing what |
74 | * happened, and a multiprecision number which pertains to the |
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75 | * event code. It may abort the search at any time by returning |
76 | * a nonzero value, which is returned as the result of the |
77 | * function. |
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78 | */ |
79 | |
80 | int dsa_seed(dsa_param *dp, unsigned l, const void *k, size_t sz, |
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81 | int (*proc)(int /*ev*/, mp */*m*/, void */*p*/), void *arg) |
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82 | { |
83 | mp *q, *p, *g; |
84 | mp *s = mp_loadb(MP_NEW, k, sz); |
85 | octet *sbuf = xmalloc(sz); |
86 | rc4_ctx rc4; |
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87 | int fail = 0; |
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88 | |
89 | l /= 8; |
90 | rc4_init(&rc4, k, sz); |
91 | |
92 | /* --- Generate @q@ --- */ |
93 | |
94 | { |
95 | octet xbuf[SHA_HASHSZ], ybuf[SHA_HASHSZ]; |
96 | sha_ctx c; |
97 | int i; |
98 | |
99 | sha_init(&c); |
100 | sha_hash(&c, k, sz); |
101 | sha_done(&c, xbuf); |
102 | |
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103 | mpx_uaddn(s->v, s->vl, 1); |
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104 | mp_storeb(s, sbuf, sz); |
105 | sha_init(&c); |
106 | sha_hash(&c, sbuf, sz); |
107 | sha_done(&c, ybuf); |
108 | |
109 | for (i = 0; i < sizeof(xbuf); i++) |
110 | xbuf[i] ^= ybuf[i]; |
111 | xbuf[0] |= 0x80; |
112 | xbuf[SHA_HASHSZ - 1] |= 0x01; |
113 | q = mp_loadb(MP_NEW, xbuf, sizeof(xbuf)); |
114 | } |
115 | |
116 | /* --- Quick primality check --- */ |
117 | |
118 | { |
119 | pgen pg; |
120 | int rc = pgen_create(&pg, q); |
121 | pgen_destroy(&pg); |
122 | if (rc == PGEN_COMPOSITE) { |
123 | if (proc) |
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124 | fail = proc(DSAEV_FAILQ, q, arg); |
125 | if (!fail) |
126 | fail = DSAEV_FAILQ; |
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127 | goto fail_0; |
128 | } |
129 | } |
130 | |
131 | /* --- Ensure that @q@ is prime --- * |
132 | * |
133 | * This requires 18 iterations, because the DSA spec is paranoid. |
134 | * Fortunately, it doesn't actually take very long. |
135 | */ |
136 | |
137 | { |
138 | rabin r; |
139 | int i; |
140 | mp *g = MP_NEW; |
141 | octet gbuf[SHA_HASHSZ]; |
142 | |
143 | rabin_create(&r, q); |
144 | for (i = 0; i < 18; i++) { |
145 | rc4_encrypt(&rc4, 0, gbuf, sizeof(gbuf)); |
146 | g = mp_loadb(g, gbuf, sizeof(gbuf)); |
147 | if (rabin_test(&r, g) == PGEN_COMPOSITE) |
148 | break; |
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149 | if (proc && (fail = proc(DSAEV_PASSQ, q, arg)) != 0) |
150 | break; |
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151 | } |
152 | mp_drop(g); |
153 | rabin_destroy(&r); |
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154 | if (fail) |
155 | goto fail_0; |
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156 | if (i < 18) { |
157 | if (proc) |
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158 | fail = proc(DSAEV_FAILQ, q, arg); |
159 | if (fail) |
160 | fail = DSAEV_FAILQ; |
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161 | goto fail_0; |
162 | } |
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163 | if (proc && (fail = proc(DSAEV_GOODQ, q, arg)) != 0) |
164 | goto fail_0; |
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165 | } |
166 | |
167 | /* --- Now generate @p@ --- * |
168 | * |
169 | * This is, unfortunately, rather more messy and complicated. |
170 | */ |
171 | |
172 | { |
173 | mp *q2 = mp_lsl(MP_NEW, q, 1); |
174 | mp *ll = mp_lsl(MP_NEW, MP_ONE, l * 8 - 1); |
175 | unsigned n = l / SHA_HASHSZ, b = l % SHA_HASHSZ; |
176 | size_t psz = SHA_HASHSZ * (n + 1); |
177 | octet *pbuf = xmalloc(psz); |
178 | sha_ctx c; |
179 | unsigned i, j; |
180 | |
181 | /* --- Fiddle with the leftover bytes count --- */ |
182 | |
183 | b = SHA_HASHSZ - b; |
184 | |
185 | /* --- Go round 4096 times trying different @p@ values --- */ |
186 | |
187 | p = MP_NEW; |
188 | for (j = 0; j < 4096; j++) { |
189 | |
190 | /* --- Build a prospective value of @p@ --- */ |
191 | |
192 | { |
193 | octet *pp = pbuf + SHA_HASHSZ * n; |
194 | |
195 | for (i = 0; i <= n; i++) { |
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196 | mpx_uaddn(s->v, s->vl, 1); |
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197 | mp_storeb(s, sbuf, sz); |
198 | sha_init(&c); |
199 | sha_hash(&c, sbuf, sz); |
200 | sha_done(&c, pp); |
201 | pp -= SHA_HASHSZ; |
202 | } |
203 | |
204 | pbuf[b] &= 0x7f; |
205 | p = mp_loadb(p, pbuf + b, psz - b); |
206 | p = mp_add(p, p, ll); |
207 | } |
208 | |
209 | /* --- Adjust @p@ so that %$p \bmod 2q = 1$% --- */ |
210 | |
211 | { |
212 | mp *c = MP_NEW; |
213 | mp_div(0, &c, p, q2); |
214 | c = mp_sub(c, c, MP_ONE); |
215 | p = mp_sub(p, p, c); |
216 | mp_drop(c); |
217 | } |
218 | |
219 | /* --- Check that @p@ is large enough --- */ |
220 | |
221 | if (MP_CMP(p, <, ll)) |
222 | continue; |
223 | |
224 | /* --- Run a simple primality test --- */ |
225 | |
226 | { |
227 | pgen pg; |
228 | int rc = pgen_create(&pg, p); |
229 | pgen_destroy(&pg); |
230 | if (rc == PGEN_COMPOSITE) |
231 | continue; |
232 | } |
233 | |
234 | /* --- Run the Rabin-Miller test --- */ |
235 | |
236 | { |
237 | rabin r; |
238 | mp *g = MP_NEW; |
239 | |
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240 | rabin_create(&r, p); |
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241 | if (proc && (fail = proc(DSAEV_TRYP, p, arg)) != 0) |
242 | break; |
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243 | for (i = 0; i < 5; i++) { |
244 | rc4_encrypt(&rc4, 0, pbuf, psz - b); |
245 | g = mp_loadb(g, pbuf, psz - b); |
246 | if (rabin_test(&r, g) == PGEN_COMPOSITE) |
247 | break; |
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248 | if (proc && (fail = proc(DSAEV_PASSP, p, arg)) != 0) |
249 | break; |
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250 | } |
251 | mp_drop(g); |
252 | rabin_destroy(&r); |
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253 | if (fail) |
254 | break; |
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255 | if (i < 5) { |
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256 | if (proc && (fail = proc(DSAEV_FAILP, p, arg)) != 0) |
257 | break; |
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258 | continue; |
259 | } |
260 | } |
261 | |
262 | /* --- It worked! --- */ |
263 | |
264 | if (proc) |
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265 | fail = proc(DSAEV_GOODP, p, arg); |
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266 | break; |
267 | } |
268 | |
269 | free(pbuf); |
270 | mp_drop(q2); |
271 | mp_drop(ll); |
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272 | if (j >= 4096 || fail) |
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273 | goto fail_1; |
274 | } |
275 | |
276 | /* --- Choose a generator of an order-%$q$% subgroup of %$Z^*_p$% --- */ |
277 | |
278 | { |
279 | mp *pp = MP_NEW; |
280 | mpw hw; |
281 | mp h; |
282 | unsigned i; |
283 | mpmont mm; |
284 | |
285 | /* --- Calculate %$p' = (p - 1)/q$% --- */ |
286 | |
287 | { |
288 | mp *p1 = mp_sub(MP_NEW, p, MP_ONE); |
289 | mp_div(&pp, 0, p1, q); |
290 | mp_drop(p1); |
291 | } |
292 | |
293 | /* --- Now find %$h$% where %$g = h^{p'} \bmod p \ne 1$% --- */ |
294 | |
295 | mp_build(&h, &hw, &hw + 1); |
296 | mpmont_create(&mm, p); |
297 | for (i = 0; i < NPRIME; i++) { |
298 | hw = ptab[i]; |
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299 | if (proc && (fail = proc(DSAEV_TRYH, &h, arg)) != 0) |
300 | break; |
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301 | g = mpmont_exp(&mm, &h, pp); |
302 | if (MP_CMP(g, !=, MP_ONE)) |
303 | break; |
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304 | mp_drop(g); |
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305 | if (proc && (fail = proc(DSAEV_FAILH, &h, arg)) != 0) |
306 | break; |
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307 | } |
308 | mp_drop(pp); |
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309 | if (fail) |
310 | goto fail_1; |
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311 | if (i >= NPRIME) { |
312 | fail = DSAEV_FAILH; |
313 | goto fail_1; |
314 | } |
315 | } |
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316 | if (proc && (fail = proc(DSAEV_GOODG, g, arg) != 0)) |
317 | goto fail_2; |
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318 | |
319 | /* --- Return the important information that I succeeded --- */ |
320 | |
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321 | dp->g = g; |
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322 | dp->p = p; |
323 | dp->q = q; |
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324 | mp_drop(s); |
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325 | free(sbuf); |
326 | return (0); |
327 | |
328 | /* --- Tidy up after failure --- */ |
329 | |
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330 | fail_2: |
331 | mp_drop(g); |
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332 | fail_1: |
333 | mp_drop(p); |
334 | fail_0: |
335 | mp_drop(q); |
336 | mp_drop(s); |
337 | free(sbuf); |
338 | return (-1); |
339 | } |
340 | |
341 | /*----- Test rig ----------------------------------------------------------*/ |
342 | |
343 | #ifdef TEST_RIG |
344 | |
345 | static char baton[] = "/-\\|"; |
346 | static char *b = baton; |
347 | |
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348 | static int event(int ev, mp *m, void *p) |
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349 | { |
350 | if (ev == DSAEV_TRYP || ev == DSAEV_PASSP) { |
351 | fputc(*b++, stdout); |
352 | fputc('\b', stdout); |
353 | fflush(stdout); |
354 | if (!*b) |
355 | b = baton; |
356 | } |
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357 | return (0); |
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358 | } |
359 | |
360 | static int verify(dstr *v) |
361 | { |
362 | mp *q = *(mp **)v[2].buf; |
363 | mp *p = *(mp **)v[3].buf; |
364 | mp *g = *(mp **)v[4].buf; |
365 | dsa_param dp; |
366 | unsigned l = *(unsigned *)v[1].buf; |
367 | int ok = 1; |
368 | int rc; |
369 | |
370 | rc = dsa_seed(&dp, l, v[0].buf, v[0].len, event, 0); |
371 | if (rc || MP_CMP(q, !=, dp.q) || |
372 | MP_CMP(p, !=, dp.p) || MP_CMP(g, !=, dp.g)) { |
373 | fputs("\n*** gen failed", stderr); |
374 | fputs("\nseed = ", stderr); type_hex.dump(&v[0], stderr); |
375 | fprintf(stderr, "\nl = %u", l); |
376 | fputs("\n q = ", stderr); mp_writefile(q, stderr, 16); |
377 | fputs("\n p = ", stderr); mp_writefile(q, stderr, 16); |
378 | fputs("\n g = ", stderr); mp_writefile(g, stderr, 16); |
379 | if (!rc) { |
380 | fputs("\ndp.q = ", stderr); mp_writefile(dp.q, stderr, 16); |
381 | fputs("\ndp.p = ", stderr); mp_writefile(dp.p, stderr, 16); |
382 | fputs("\ndp.g = ", stderr); mp_writefile(dp.g, stderr, 16); |
383 | } |
384 | fputc('\n', stderr); |
385 | ok = 0; |
386 | } |
387 | |
388 | mp_drop(q); mp_drop(p); mp_drop(g); |
389 | if (!rc) { |
390 | mp_drop(dp.q); mp_drop(dp.p); mp_drop(dp.g); |
391 | } |
392 | return (ok); |
393 | } |
394 | |
395 | static test_chunk tests[] = { |
396 | { "gen", verify, |
397 | { &type_hex, &type_int, &type_mp, &type_mp, &type_mp, 0 } }, |
398 | { 0, 0, { 0 } } |
399 | }; |
400 | |
401 | int main(int argc, char *argv[]) |
402 | { |
403 | sub_init(); |
404 | test_run(argc, argv, tests, SRCDIR "/tests/dsa"); |
405 | return (0); |
406 | } |
407 | |
408 | #endif |
409 | |
410 | /*----- That's all, folks -------------------------------------------------*/ |