/* -*-c-*-
*
- * $Id: mpmont.c,v 1.17 2004/04/01 12:50:09 mdw Exp $
+ * $Id$
*
* Montgomery reduction
*
* (c) 1999 Straylight/Edgeware
*/
-/*----- Licensing notice --------------------------------------------------*
+/*----- Licensing notice --------------------------------------------------*
*
* This file is part of Catacomb.
*
* 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: mpmont.c,v $
- * Revision 1.17 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 1.16 2002/01/13 13:40:31 mdw
- * Avoid trashing arguments before we've used them.
- *
- * Revision 1.15 2001/06/16 13:00:20 mdw
- * Use the generic exponentiation functions.
- *
- * Revision 1.14 2001/02/22 09:04:26 mdw
- * Cosmetic fix.
- *
- * Revision 1.13 2001/02/03 12:00:29 mdw
- * Now @mp_drop@ checks its argument is non-NULL before attempting to free
- * it. Note that the macro version @MP_DROP@ doesn't do this.
- *
- * Revision 1.12 2000/10/08 15:48:35 mdw
- * Rename Karatsuba constants now that we have @gfx_kmul@ too.
- *
- * Revision 1.11 2000/10/08 12:04:27 mdw
- * (mpmont_reduce, mpmont_mul): Cope with negative numbers.
- *
- * Revision 1.10 2000/07/29 17:05:43 mdw
- * (mpmont_expr): Use sliding window exponentiation, with a drop-through
- * for small exponents to use a simple left-to-right bitwise routine. This
- * can reduce modexp times by up to a quarter.
- *
- * Revision 1.9 2000/06/17 11:45:09 mdw
- * Major memory management overhaul. Added arena support. Use the secure
- * arena for secret integers. Replace and improve the MP management macros
- * (e.g., replace MP_MODIFY by MP_DEST).
- *
- * Revision 1.8 1999/12/22 15:55:00 mdw
- * Adjust Karatsuba parameters.
- *
- * Revision 1.7 1999/12/11 01:51:14 mdw
- * Use a Karatsuba-based reduction for large moduli.
- *
- * Revision 1.6 1999/12/10 23:18:39 mdw
- * Change interface for suggested destinations.
- *
- * Revision 1.5 1999/11/22 13:58:40 mdw
- * Add an option to disable Montgomery reduction, so that performance
- * comparisons can be done.
- *
- * Revision 1.4 1999/11/21 12:27:06 mdw
- * Remove a division from the Montgomery setup by calculating
- * %$R^2 \bmod m$% first and then %$R \bmod m$% by Montgomery reduction of
- * %$R^2$%.
- *
- * Revision 1.3 1999/11/21 11:35:10 mdw
- * Performance improvement: use @mp_sqr@ and @mpmont_reduce@ instead of
- * @mpmont_mul@ for squaring in exponentiation.
- *
- * Revision 1.2 1999/11/19 13:17:26 mdw
- * Add extra interface to exponentiation which returns a Montgomerized
- * result.
- *
- * Revision 1.1 1999/11/17 18:02:16 mdw
- * New multiprecision integer arithmetic suite.
- *
- */
-
/*----- Header files ------------------------------------------------------*/
#include "mp.h"
* Arguments: @mpmont *mm@ = pointer to Montgomery reduction context
* @mp *m@ = modulus to use
*
- * Returns: ---
+ * Returns: Zero on success, nonzero on error.
*
* Use: Initializes a Montgomery reduction context ready for use.
* The argument @m@ must be a positive odd integer.
#ifdef MPMONT_DISABLE
-void mpmont_create(mpmont *mm, mp *m)
+int mpmont_create(mpmont *mm, mp *m)
{
mp_shrink(m);
mm->m = MP_COPY(m);
mm->r = MP_ONE;
mm->r2 = MP_ONE;
mm->mi = MP_ONE;
+ return (0);
}
#else
-void mpmont_create(mpmont *mm, mp *m)
+int mpmont_create(mpmont *mm, mp *m)
{
size_t n = MP_LEN(m);
mp *r2 = mp_new(2 * n + 1, 0);
mp r;
- /* --- Validate the arguments --- */
-
- assert(((void)"Montgomery modulus must be positive",
- (m->f & MP_NEG) == 0));
- assert(((void)"Montgomery modulus must be odd", m->v[0] & 1));
-
/* --- Take a copy of the modulus --- */
- mp_shrink(m);
+ if (!MP_POSP(m) || !MP_ODDP(m))
+ return (-1);
mm->m = MP_COPY(m);
/* --- Determine %$R^2$% --- */
/* --- Find the magic value @mi@ --- */
mp_build(&r, r2->v + n, r2->vl);
- mm->mi = MP_NEW;
- mp_gcd(0, 0, &mm->mi, &r, m);
+ mm->mi = mp_modinv(MP_NEW, m, &r);
mm->mi = mp_sub(mm->mi, &r, mm->mi);
/* --- Discover the values %$R \bmod m$% and %$R^2 \bmod m$% --- */
mp_div(0, &mm->r2, r2, m);
mm->r = mpmont_reduce(mm, MP_NEW, mm->r2);
MP_DROP(r2);
+ return (0);
}
#endif
fputs("\n*** bad r", stderr);
fputs("\nm = ", stderr); mp_writefile(m, stderr, 10);
fputs("\nexpected ", stderr); mp_writefile(r, stderr, 10);
- fputs("\n found ", stderr); mp_writefile(mm.r, stderr, 10);
+ fputs("\n found ", stderr); mp_writefile(mm.r, stderr, 10);
fputc('\n', stderr);
ok = 0;
}
fputs("\n*** bad r2", stderr);
fputs("\nm = ", stderr); mp_writefile(m, stderr, 10);
fputs("\nexpected ", stderr); mp_writefile(r2, stderr, 10);
- fputs("\n found ", stderr); mp_writefile(mm.r2, stderr, 10);
+ fputs("\n found ", stderr); mp_writefile(mm.r2, stderr, 10);
fputc('\n', stderr);
ok = 0;
}
projects / u / mdw / catacomb / blobdiff