/* -*-c-*-
*
- * $Id: mpbarrett.c,v 1.9 2004/04/01 12:50:09 mdw Exp $
+ * $Id$
*
* Barrett modular 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: mpbarrett.c,v $
- * Revision 1.9 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 1.8 2001/06/16 13:00:20 mdw
- * Use the generic exponentiation functions.
- *
- * Revision 1.7 2001/04/19 18:25:26 mdw
- * Use sliding-window exponentiation.
- *
- * Revision 1.6 2000/10/08 12:03:44 mdw
- * (mpbarrett_reduce): Cope with negative numbers.
- *
- * Revision 1.5 2000/07/29 17:04:33 mdw
- * Change to use left-to-right bitwise exponentiation. This will improve
- * performance when the base is small.
- *
- * Revision 1.4 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 1.3 1999/12/12 15:08:52 mdw
- * Don't bother shifting %$q$% in @mpbarrett_reduce@, just skip the least
- * significant digits.
- *
- * Revision 1.2 1999/12/11 01:50:56 mdw
- * Improve initialization slightly.
- *
- * Revision 1.1 1999/12/10 23:21:59 mdw
- * Barrett reduction support: works with even moduli.
- *
- */
-
/*----- Header files ------------------------------------------------------*/
#include "mp.h"
* @mp *m@ = modulus to work to
*
*
- * Returns: ---
+ * Returns: Zero on success, nonzero on error.
*
* Use: Initializes a Barrett reduction context ready for use.
*/
-void mpbarrett_create(mpbarrett *mb, mp *m)
+int mpbarrett_create(mpbarrett *mb, mp *m)
{
mp *b;
/* --- Validate the arguments --- */
- assert(((void)"Barrett modulus must be positive", (m->f & MP_NEG) == 0));
+ if (!MP_POSP(m))
+ return (-1);
/* --- Compute %$\mu$% --- */
b->vl[-1] = 1;
mp_div(&b, 0, b, m);
mb->mu = b;
+ return (0);
}
/* --- @mpbarrett_destroy@ --- *
m = MP_COPY(m);
if (d)
MP_DROP(d);
+ MP_DROP(q);
return (m);
}
}
mvl = m->v + k + 1;
r = mp_new(k + 1, (q->f | mb->m->f) & MP_BURN);
mpx_umul(r->v, r->vl, q->v + k + 1, q->vl, mb->m->v, mb->m->vl);
- MP_DEST(d, k + 1, r->f);
+ MP_DEST(d, k + 1, r->f | MP_UNDEF);
mpx_usub(d->v, d->vl, m->v, mvl, r->v, r->vl);
d->f = (m->f | r->f) & (MP_BURN | MP_NEG);
MP_DROP(r);