git.distorted.org.uk Git - u/mdw/catacomb/blob - dsa-gen.c

   1 /* -*-c-*-
   2  *
   3  * $Id: dsa-gen.c,v 1.5 2000/02/12 18:21:02 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 1.5  2000/02/12 18:21:02  mdw
  34  * Overhaul of key management (again).
  35  *
  36  * Revision 1.4  1999/12/22 15:52:44  mdw
  37  * Reworking for new prime-search system.
  38  *
  39  * Revision 1.3  1999/12/10 23:18:38  mdw
  40  * Change interface for suggested destinations.
  41  *
  42  * Revision 1.2  1999/11/20 22:23:48  mdw
  43  * Allow event handler to abort the search process.
  44  *
  45  * Revision 1.1  1999/11/19 19:28:00  mdw
  46  * Implementation of the Digital Signature Algorithm.
  47  *
  48  */
  49
  50 /*----- Header files ------------------------------------------------------*/
  51
  52 #include <stdio.h>
  53 #include <stdlib.h>
  54
  55 #include "dsa.h"
  56 #include "dsarand.h"
  57 #include "fibrand.h"
  58 #include "mp.h"
  59 #include "mprand.h"
  60 #include "pgen.h"
  61 #include "prim.h"
  62 #include "primorial.h"
  63 #include "sha.h"
  64
  65 /*----- The DSA stepper ---------------------------------------------------*/
  66
  67 /* --- @next@ --- *
  68  *
  69  * Arguments:   @pgen_event *ev@ = pointer to event block
  70  *              @dsa_stepctx *d@ = pointer to stepping context
  71  *
  72  * Returns:     A @PGEN@ result code.
  73  *
  74  * Use:         Steps the generator once, reads the result, and tests it.
  75  */
  76
  77 static int next(pgen_event *ev, dsa_stepctx *d)
  78 {
  79   mp *m;
  80   int rc;
  81
  82   /* --- Load the new candidate --- */
  83
  84   m = mprand(ev->m, d->bits, d->r, d->or);
  85
  86   /* --- Force to be a multiple of @q@ --- */
  87
  88   if (d->q) {
  89     mp *r = MP_NEW;
  90     mp_div(0, &r, m, d->q);
  91     m = mp_sub(m, m, r);
  92     mp_drop(r);
  93   }
  94   m->v[0] |= d->or;
  95   ev->m = m;
  96
  97   /* --- Do the trial division --- */
  98
  99   {
 100     mp *g = MP_NEW;
 101     mp_gcd(&g, 0, 0, m, primorial);
 102     if (MP_CMP(g, ==, MP_ONE) || MP_CMP(g, ==, m))
 103       rc = PGEN_TRY;
 104     else
 105       rc = PGEN_FAIL;
 106     mp_drop(g);
 107   }
 108
 109   /* --- Return the result --- */
 110
 111   return (rc);
 112 }
 113
 114 /* --- @dsa_step@ --- */
 115
 116 int dsa_step(int rq, pgen_event *ev, void *p)
 117 {
 118   dsa_stepctx *d = p;
 119
 120   switch (rq) {
 121     case PGEN_BEGIN:
 122       primorial_setup();
 123     case PGEN_TRY:
 124       return (next(ev, d));
 125     case PGEN_DONE:
 126       return (PGEN_DONE);
 127   }
 128   return (PGEN_ABORT);
 129 }
 130
 131 /*----- Glue code ---------------------------------------------------------*/
 132
 133 /* --- @dsa_seed@ --- *
 134  *
 135  * Arguments:   @dsa_param *dp@ = where to store parameters
 136  *              @unsigned ql@ = length of @q@ in bits
 137  *              @unsigned pl@ = length of @p@ in bits
 138  *              @unsigned steps@ = number of steps to find @q@
 139  *              @const void *k@ = pointer to key material
 140  *              @size_t sz@ = size of key material
 141  *              @pgen_proc *event@ = event handler function
 142  *              @void *ectx@ = argument for event handler
 143  *
 144  * Returns:     @PGEN_DONE@ if everything worked ok; @PGEN_ABORT@ otherwise.
 145  *
 146  * Use:         Generates the DSA shared parameters from a given seed value.
 147  *
 148  *              The parameters are a prime %$q$%, relatively small, and a
 149  *              large prime %$p = kq + 1$% for some %$k$%, together with a
 150  *              generator %$g$% of the cyclic subgroup of order %$q$%.  These
 151  *              are actually the same as the Diffie-Hellman parameter set,
 152  *              but the generation algorithm is different.
 153  *
 154  *              The algorithm used is a compatible extension of the method
 155  *              described in the DSA standard, FIPS 186.  The standard
 156  *              requires that %$q$% be 160 bits in size (i.e., @ql == 160@)
 157  *              and that the length of %$p$% be %$L = 512 + 64l$% for some
 158  *              %$l$%.  Neither limitation applies to this implementation.
 159  */
 160
 161 int dsa_seed(dsa_param *dp, unsigned ql, unsigned pl, unsigned steps,
 162              const void *k, size_t sz, pgen_proc *event, void *ectx)
 163 {
 164   dsa_stepctx s;
 165   prim_ctx p;
 166   int i;
 167   rabin r;
 168   mp *qc;
 169
 170   /* --- Initialize the stepping context --- */
 171
 172   s.r = dsarand_create(k, sz);
 173   s.or = 1;
 174
 175   /* --- Find @q@ --- */
 176
 177   s.q = 0;
 178   s.r->ops->misc(s.r, DSARAND_PASSES, 2);
 179   s.bits = ql;
 180   if ((dp->q = pgen("q", MP_NEW, MP_NEW, event, ectx, steps, dsa_step, &s,
 181                     rabin_iters(ql), pgen_test, &r)) == 0)
 182     goto fail_q;
 183
 184   /* --- Find @p@ --- */
 185
 186   s.q = mp_lsl(MP_NEW, dp->q, 1);
 187   s.r->ops->misc(s.r, DSARAND_PASSES, 1);
 188   s.bits = pl;
 189   if ((dp->p = pgen("p", MP_NEW, MP_NEW, event, ectx, 4096, dsa_step, &s,
 190                     rabin_iters(pl), pgen_test, &r)) == 0)
 191     goto fail_p;
 192   mp_drop(s.q);
 193
 194   /* --- Find @g@ --- *
 195    *
 196    * The division returns remainder 1.  This doesn't matter.
 197    */
 198
 199   mpmont_create(&p.mm, dp->p);
 200   qc = MP_NEW; mp_div(&qc, 0, dp->p, dp->q);
 201   i = 0;
 202   p.f = qc;
 203   p.n = 0;
 204   if ((dp->g = pgen("g", MP_NEW, MP_NEW, event, ectx, 0, prim_step, &i,
 205                     1, prim_test, &p)) == 0)
 206     goto fail_g;
 207
 208   /* --- Done --- */
 209
 210   mp_drop(qc);
 211   mpmont_destroy(&p.mm);
 212   s.r->ops->destroy(s.r);
 213   return (PGEN_DONE);
 214
 215   /* --- Tidy up when things go wrong --- */
 216
 217 fail_g:
 218   mp_drop(qc);
 219   mpmont_destroy(&p.mm);
 220 fail_p:
 221   mp_drop(dp->q);
 222   mp_drop(s.q);
 223 fail_q:
 224   s.r->ops->destroy(s.r);
 225   return (PGEN_ABORT);
 226 }
 227
 228 /*----- Test rig ----------------------------------------------------------*/
 229
 230 #ifdef TEST_RIG
 231
 232 static int verify(dstr *v)
 233 {
 234   mp *q = *(mp **)v[2].buf;
 235   mp *p = *(mp **)v[3].buf;
 236   mp *g = *(mp **)v[4].buf;
 237   dsa_param dp;
 238   unsigned l = *(unsigned *)v[1].buf;
 239   int ok = 1;
 240   int rc;
 241
 242   rc = dsa_seed(&dp, 160, l, 1, v[0].buf, v[0].len, pgen_evspin, 0);
 243   if (rc || MP_CMP(q, !=, dp.q) ||
 244       MP_CMP(p, !=, dp.p) || MP_CMP(g, !=, dp.g)) {
 245     fputs("\n*** gen failed", stderr);
 246     fputs("\nseed = ", stderr); type_hex.dump(&v[0], stderr);
 247     fprintf(stderr, "\nl = %u", l);
 248     fputs("\n   q = ", stderr); mp_writefile(q, stderr, 16);
 249     fputs("\n   p = ", stderr); mp_writefile(p, stderr, 16);
 250     fputs("\n   g = ", stderr); mp_writefile(g, stderr, 16);
 251     if (!rc) {
 252       fputs("\ndp.q = ", stderr); mp_writefile(dp.q, stderr, 16);
 253       fputs("\ndp.p = ", stderr); mp_writefile(dp.p, stderr, 16);
 254       fputs("\ndp.g = ", stderr); mp_writefile(dp.g, stderr, 16);
 255     }
 256     fputc('\n', stderr);
 257     ok = 0;
 258   }
 259
 260   mp_drop(q); mp_drop(p); mp_drop(g);
 261   if (!rc) {
 262     mp_drop(dp.q); mp_drop(dp.p); mp_drop(dp.g);
 263   }
 264   assert(mparena_count(MPARENA_GLOBAL) == 1); /* Primorial! */
 265   return (ok);
 266 }
 267
 268 static test_chunk tests[] = {
 269   { "gen", verify,
 270     { &type_hex, &type_int, &type_mp, &type_mp, &type_mp, 0 }  },
 271   { 0, 0, { 0 } }
 272 };
 273
 274 int main(int argc, char *argv[])
 275 {
 276   sub_init();
 277   test_run(argc, argv, tests, SRCDIR "/tests/dsa");
 278   return (0);
 279 }
 280
 281 #endif
 282
 283 /*----- That's all, folks -------------------------------------------------*/