Add cyclic group abstraction, with test code. Separate off exponentation

[u/mdw/catacomb] / mpbarrett-mexp.c

/* -*-c-*-
 *
 * $Id: mpbarrett-mexp.c,v 1.2 2004/04/01 12:50:09 mdw Exp $
 *
 * Multiple simultaneous exponentiations
 *
 * (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.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: mpbarrett-mexp.c,v $
 * Revision 1.2  2004/04/01 12:50:09  mdw
 * Add cyclic group abstraction, with test code.  Separate off exponentation
 * functions for better static linking.  Fix a buttload of bugs on the way.
 * Generally ensure that negative exponents do inversion correctly.  Add
 * table of standard prime-field subgroups.  (Binary field subgroups are
 * currently unimplemented but easy to add if anyone ever finds a good one.)
 *
 * Revision 1.1  2001/06/16 12:58:34  mdw
 * Added simultaneous exponentiation with Barrett reduction.
 *
 */

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

#include "mp.h"
#include "mpbarrett.h"

#define EXP_WINSZ 3
#include "mpbarrett-exp.h"

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

/* --- @mpbarrett_mexp@ --- *
 *
 * Arguments:	@mpbarrett *mb@ = pointer to Barrett reduction context
 *		@mp *d@ = fake destination
 *		@const mp_expfactor *f@ = pointer to array of factors
 *		@size_t n@ = number of factors supplied
 *
 * Returns:	If the bases are %$g_0, g_1, \ldots, g_{n-1}$% and the
 *		exponents are %$e_0, e_1, \ldots, e_{n-1}$% then the result
 *		is:
 *
 *		%$g_0^{e_0} g_1^{e_1} \ldots g_{n-1}^{e_{n-1}} \bmod m$%
 */

mp *mpbarrett_mexp(mpbarrett *mb, mp *d, const mp_expfactor *f, size_t n)
{
  mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
  mp *a = MP_ONE;
  mp *spare;
  mp *g = MP_NEW;
  size_t i;

  spare = MP_NEW;
  for (i = 0; i < n; i++) {
    if (f[i].exp->f & MP_BURN)
      spare = MP_NEWSEC;
    if (!(f[i].exp->f & MP_NEG))
      ff[i].base = MP_COPY(f[i].base);
    else {
      ff[i].base = MP_NEW;
      mp_gcd(&g, 0, &ff[i].base, mb->m, f[i].base);
      assert(MP_EQ(g, MP_ONE));
    }
    ff[i].exp = f[i].exp;
  }
  mp_drop(g);
  EXP_SIMUL(a, ff, n);
  mp_drop(d);
  mp_drop(spare);
  for (i = 0; i < n; i++)
    mp_drop(ff[i].base);
  xfree(ff);
  return (a);
}

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

#ifdef TEST_RIG

#include <mLib/testrig.h>

static int verify(size_t n, dstr *v)
{
  mp *m = *(mp **)v[0].buf;
  mp_expfactor *f = xmalloc(n * sizeof(*f));
  mp *r, *rr;
  size_t i, j;
  mpbarrett mb;
  int ok = 1;

  j = 1;
  for (i = 0; i < n; i++) {
    f[i].base = *(mp **)v[j++].buf;
    f[i].exp = *(mp **)v[j++].buf;
  }

  rr = *(mp **)v[j].buf;
  mpbarrett_create(&mb, m);
  r = mpbarrett_mexp(&mb, MP_NEW, f, n);
  if (!MP_EQ(r, rr)) {
    fputs("\n*** mexp failed\n", stderr);
    fputs("m = ", stderr); mp_writefile(m, stderr, 10);
    for (i = 0; i < n; i++) {
      fprintf(stderr, "\ng_%u = ", i);
      mp_writefile(f[i].base, stderr, 10);
      fprintf(stderr, "\ne_%u = ", i);
      mp_writefile(f[i].exp, stderr, 10);
    }
    fputs("\nr = ", stderr); mp_writefile(r, stderr, 10);
    fputs("\nR = ", stderr); mp_writefile(rr, stderr, 10);
    fputc('\n', stderr);
    ok = 0;
  }

  for (i = 0; i < n; i++) {
    MP_DROP(f[i].base);
    MP_DROP(f[i].exp);
  }
  MP_DROP(m);
  MP_DROP(r);
  MP_DROP(rr);
  mpbarrett_destroy(&mb);
  assert(mparena_count(MPARENA_GLOBAL) == 0);
  return (ok);
}

static int t1(dstr *v) { return verify(1, v); }
static int t2(dstr *v) { return verify(2, v); }
static int t3(dstr *v) { return verify(3, v); }
static int t4(dstr *v) { return verify(4, v); }
static int t5(dstr *v) { return verify(5, v); }

static test_chunk tests[] = {
  { "mexp-1", t1, { &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, 0 } },
  { "mexp-2", t2, { &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, 0 } },
  { "mexp-3", t3, { &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, 0 } },
  { "mexp-4", t4, { &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, 0 } },
  { "mexp-5", t5, { &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, &type_mp,
		    &type_mp, 0 } },
  { 0, 0, { 0 } }
};

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

#endif

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