| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: dsa-gen.c,v 1.2 1999/11/20 22:23:48 mdw Exp $ |
| 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 $ |
| 33 | * Revision 1.2 1999/11/20 22:23:48 mdw |
| 34 | * Allow event handler to abort the search process. |
| 35 | * |
| 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 |
| 60 | * @int (*proc)(int ev, mp *m, void *p)@ = event procedure |
| 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 |
| 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. |
| 78 | */ |
| 79 | |
| 80 | int dsa_seed(dsa_param *dp, unsigned l, const void *k, size_t sz, |
| 81 | int (*proc)(int /*ev*/, mp */*m*/, void */*p*/), void *arg) |
| 82 | { |
| 83 | mp *q, *p, *g; |
| 84 | mp *s = mp_loadb(MP_NEW, k, sz); |
| 85 | octet *sbuf = xmalloc(sz); |
| 86 | rc4_ctx rc4; |
| 87 | int fail = 0; |
| 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 | |
| 103 | mpx_uaddn(s->v, s->vl, 1); |
| 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) |
| 124 | fail = proc(DSAEV_FAILQ, q, arg); |
| 125 | if (!fail) |
| 126 | fail = DSAEV_FAILQ; |
| 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; |
| 149 | if (proc && (fail = proc(DSAEV_PASSQ, q, arg)) != 0) |
| 150 | break; |
| 151 | } |
| 152 | mp_drop(g); |
| 153 | rabin_destroy(&r); |
| 154 | if (fail) |
| 155 | goto fail_0; |
| 156 | if (i < 18) { |
| 157 | if (proc) |
| 158 | fail = proc(DSAEV_FAILQ, q, arg); |
| 159 | if (fail) |
| 160 | fail = DSAEV_FAILQ; |
| 161 | goto fail_0; |
| 162 | } |
| 163 | if (proc && (fail = proc(DSAEV_GOODQ, q, arg)) != 0) |
| 164 | goto fail_0; |
| 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++) { |
| 196 | mpx_uaddn(s->v, s->vl, 1); |
| 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 | |
| 240 | rabin_create(&r, p); |
| 241 | if (proc && (fail = proc(DSAEV_TRYP, p, arg)) != 0) |
| 242 | break; |
| 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; |
| 248 | if (proc && (fail = proc(DSAEV_PASSP, p, arg)) != 0) |
| 249 | break; |
| 250 | } |
| 251 | mp_drop(g); |
| 252 | rabin_destroy(&r); |
| 253 | if (fail) |
| 254 | break; |
| 255 | if (i < 5) { |
| 256 | if (proc && (fail = proc(DSAEV_FAILP, p, arg)) != 0) |
| 257 | break; |
| 258 | continue; |
| 259 | } |
| 260 | } |
| 261 | |
| 262 | /* --- It worked! --- */ |
| 263 | |
| 264 | if (proc) |
| 265 | fail = proc(DSAEV_GOODP, p, arg); |
| 266 | break; |
| 267 | } |
| 268 | |
| 269 | free(pbuf); |
| 270 | mp_drop(q2); |
| 271 | mp_drop(ll); |
| 272 | if (j >= 4096 || fail) |
| 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]; |
| 299 | if (proc && (fail = proc(DSAEV_TRYH, &h, arg)) != 0) |
| 300 | break; |
| 301 | g = mpmont_exp(&mm, &h, pp); |
| 302 | if (MP_CMP(g, !=, MP_ONE)) |
| 303 | break; |
| 304 | mp_drop(g); |
| 305 | if (proc && (fail = proc(DSAEV_FAILH, &h, arg)) != 0) |
| 306 | break; |
| 307 | } |
| 308 | mp_drop(pp); |
| 309 | if (fail) |
| 310 | goto fail_1; |
| 311 | if (i >= NPRIME) { |
| 312 | fail = DSAEV_FAILH; |
| 313 | goto fail_1; |
| 314 | } |
| 315 | } |
| 316 | if (proc && (fail = proc(DSAEV_GOODG, g, arg) != 0)) |
| 317 | goto fail_2; |
| 318 | |
| 319 | /* --- Return the important information that I succeeded --- */ |
| 320 | |
| 321 | dp->g = g; |
| 322 | dp->p = p; |
| 323 | dp->q = q; |
| 324 | mp_drop(s); |
| 325 | free(sbuf); |
| 326 | return (0); |
| 327 | |
| 328 | /* --- Tidy up after failure --- */ |
| 329 | |
| 330 | fail_2: |
| 331 | mp_drop(g); |
| 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 | |
| 348 | static int event(int ev, mp *m, void *p) |
| 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 | } |
| 357 | return (0); |
| 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 -------------------------------------------------*/ |