[catacomb] / pub / dsa-sign.c

/* -*-c-*-
 *
 * DSA signing operation
 *
 * (c) 1999 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of Catacomb.
 *
 * Catacomb is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * Catacomb is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with Catacomb; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include "dsa.h"
#include "mp.h"
#include "mpbarrett.h"
#include "mpmont.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @dsa_mksig@ --- *
 *
 * Arguments:   @const dsa_param *dp@ = pointer to DSA parameters
 *              @mp *a@ = secret signing key
 *              @mp *m@ = message to be signed
 *              @mp *k@ = random data
 *              @mp **rr, **ss@ = where to put output parameters
 *
 * Returns:     ---
 *
 * Use:         Computes a DSA signature of a message.
 */

void dsa_mksig(const dsa_param *dp, mp *a, mp *m, mp *k, mp **rr, mp **ss)
{
  mpmont pm;
  mpbarrett qb;
  mp *k1, *r;
  mp *ar;

  /* --- Compute %$r = (g^k \bmod p) \bmod q$% --- */

  mpmont_create(&pm, dp->p);
  r = mpmont_exp(&pm, MP_NEW, dp->g, k);
  mpmont_destroy(&pm);
  mp_div(0, &r, r, dp->q);

  /* --- Compute %$k^{-1} \bmod q$% --- */

  k1 = mp_modinv(MP_NEW, k, dp->q);

  /* --- Now for %$k^{-1}(m + ar)$% --- */

  mpbarrett_create(&qb, dp->q);
  ar = mp_mul(MP_NEW, a, r);
  ar = mp_add(ar, ar, m);
  ar = mpbarrett_reduce(&qb, ar, ar);
  ar = mp_mul(ar, ar, k1);
  ar = mpbarrett_reduce(&qb, ar, ar);
  mpbarrett_destroy(&qb);
  MP_DROP(k1);
  if (*rr) MP_DROP(*rr);
  if (*ss) MP_DROP(*ss);
  *rr = r;
  *ss = ar;
}

/* --- @dsa_sign@ --- *
 *
 * Arguments:   @dsa_param *dp@ = pointer to DSA parameters
 *              @mp *a@ = pointer to secret signing key
 *              @const void *m@ = pointer to message
 *              @size_t msz@ = size of the message
 *              @const void *k@ = secret random data for securing signature
 *              @size_t ksz@ = size of secret data
 *              @void *r@ = pointer to output space for @r@
 *              @size_t rsz@ = size of output space for @r@
 *              @void *s@ = pointer to output space for @s@
 *              @size_t ssz@ = size of output space for @s@
 *
 * Returns:     ---
 *
 * Use:         Signs a message, storing the results in a big-endian binary
 *              form.
 */

void dsa_sign(dsa_param *dp, mp *a,
              const void *m, size_t msz, const void *k, size_t ksz,
              void *r, size_t rsz, void *s, size_t ssz)
{
  mp *mm = dsa_h2n(MP_NEW, dp->q, m, msz);
  mp *km = mp_loadb(MP_NEW, k, ksz);
  mp *rm = MP_NEW, *sm = MP_NEW;
  dsa_mksig(dp, a, mm, km, &rm, &sm);
  mp_storeb(rm, r, rsz);
  mp_storeb(sm, s, ssz);
  mp_drop(mm); mp_drop(km);
  mp_drop(rm); mp_drop(sm);
}

/*----- Test rig ----------------------------------------------------------*/

#ifdef TEST_RIG

#include <mLib/testrig.h>

#include "sha.h"

static int verify(dstr *v)
{
  dsa_param dp;
  mp *x;
  sha_ctx c;
  octet hash[SHA_HASHSZ];
  dsa_sig s;
  int ok = 1;

  dp.q = *(mp **)v[0].buf;
  dp.p = *(mp **)v[1].buf;
  dp.g = *(mp **)v[2].buf;
  x = *(mp **)v[3].buf;

  sha_init(&c);
  sha_hash(&c, v[4].buf, v[4].len);
  sha_done(&c, hash);

  dsa_sign(&dp, x, hash, sizeof(hash), v[5].buf, v[5].len,
           s.r, sizeof(s.r), s.s, sizeof(s.s));

  if (v[6].len != sizeof(s.r) || v[7].len != sizeof(s.s) ||
      memcmp(s.r, v[6].buf, sizeof(s.r)) != 0 ||
      memcmp(s.s, v[7].buf, sizeof(s.s)) != 0) {
    fputs("\n*** signature failed", stderr);
    fputs("\nq = ", stderr); mp_writefile(dp.q, stderr, 16);
    fputs("\np = ", stderr); mp_writefile(dp.p, stderr, 16);
    fputs("\ng = ", stderr); mp_writefile(dp.g, stderr, 16);
    fputs("\nx = ", stderr); mp_writefile(x, stderr, 16);
    fprintf(stderr, "\nmessage = `%s'", v[4].buf);
    fputs("\nk = ", stderr); type_hex.dump(&v[5], stderr);
    fputs("\nR = ", stderr); type_hex.dump(&v[6], stderr);
    fputs("\nS = ", stderr); type_hex.dump(&v[7], stderr);

    {
      mp *m = MP_NEW;
      m = mp_loadb(m, hash, sizeof(hash));
      fputs("\nm = ", stderr); mp_writefile(m, stderr, 16);
      m = mp_loadb(m, s.r, sizeof(s.r));
      fputs("\nr = ", stderr); mp_writefile(m, stderr, 16);
      m = mp_loadb(m, s.s, sizeof(s.s));
      fputs("\ns = ", stderr); mp_writefile(m, stderr, 16);
      mp_drop(m);
    }

    fputc('\n', stderr);
    ok = 0;
  }

  mp_drop(dp.p);
  mp_drop(dp.q);
  mp_drop(dp.g);
  mp_drop(x);
  assert(mparena_count(MPARENA_GLOBAL) == 0);
  return (ok);
}

static test_chunk tests[] = {
  { "sign", verify,
    { &type_mp, &type_mp, &type_mp, &type_mp,
      &type_string, &type_hex, &type_hex, &type_hex, 0 } },
  { 0, 0, { 0 } }
};

int main(int argc, char *argv[])
{
  sub_init();
  test_run(argc, argv, tests, SRCDIR "/t/dsa");
  return (0);
}

#endif

/*----- That's all, folks -------------------------------------------------*/