X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/4640a0dd947f422cfda780c62da342792af27b7b..7280f7f44cfae62f6d34761ac88aa19da7da5dd8:/mpbarrett.c

diff --git a/mpbarrett.c b/mpbarrett.c
index b38aa91..13210b3 100644
--- a/mpbarrett.c
+++ b/mpbarrett.c
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: mpbarrett.c,v 1.8 2001/06/16 13:00:20 mdw Exp $
+ * $Id$
  *
  * Barrett modular reduction
  *
  * (c) 1999 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Catacomb.
  *
@@ -15,56 +15,22 @@
  * 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 1.8  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"
 #include "mpbarrett.h"
-#include "mpbarrett-exp.h"
 
 /*----- Main code ---------------------------------------------------------*/
 
@@ -74,18 +40,19 @@
  *		@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 %$\mu$% --- */
 
@@ -97,6 +64,7 @@ void mpbarrett_create(mpbarrett *mb, mp *m)
   b->vl[-1] = 1;
   mp_div(&b, 0, b, m);
   mb->mu = b;
+  return (0);
 }
 
 /* --- @mpbarrett_destroy@ --- *
@@ -151,6 +119,7 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *m)
       m = MP_COPY(m);
       if (d)
 	MP_DROP(d);
+      MP_DROP(q);
       return (m);
     }
   }
@@ -168,7 +137,7 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *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);
@@ -193,33 +162,6 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *m)
   return (d);
 }
 
-/* --- @mpbarrett_exp@ --- *
- *
- * Arguments:	@mpbarrett *mb@ = pointer to Barrett reduction context
- *              @mp *d@ = fake destination
- *              @mp *a@ = base
- *              @mp *e@ = exponent
- *
- * Returns:     Result, %$a^e \bmod m$%.
- */
-
-mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e)
-{
-  mp *x = MP_ONE;
-  mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
-
-  MP_SHRINK(e);
-  if (!MP_LEN(e))
-    ;
-  else if (MP_LEN(e) < EXP_THRESH)
-    EXP_SIMPLE(x, a, e);
-  else
-    EXP_WINDOW(x, a, e);
-  mp_drop(d);
-  mp_drop(spare);
-  return (x);
-}
-
 /*----- Test rig ----------------------------------------------------------*/
 
 #ifdef TEST_RIG
@@ -254,44 +196,8 @@ static int vmod(dstr *v)
   return (ok);
 }
 
-static int vexp(dstr *v)
-{
-  mp *m = *(mp **)v[0].buf;
-  mp *a = *(mp **)v[1].buf;
-  mp *b = *(mp **)v[2].buf;
-  mp *r = *(mp **)v[3].buf;
-  mp *mr;
-  int ok = 1;
-
-  mpbarrett mb;
-  mpbarrett_create(&mb, m);
-
-  mr = mpbarrett_exp(&mb, MP_NEW, a, b);
-
-  if (!MP_EQ(mr, r)) {
-    fputs("\n*** barrett modexp failed", stderr);
-    fputs("\n m = ", stderr); mp_writefile(m, stderr, 10);
-    fputs("\n a = ", stderr); mp_writefile(a, stderr, 10);
-    fputs("\n e = ", stderr); mp_writefile(b, stderr, 10);
-    fputs("\n r = ", stderr); mp_writefile(r, stderr, 10);
-    fputs("\nmr = ", stderr); mp_writefile(mr, stderr, 10);
-    fputc('\n', stderr);
-    ok = 0;
-  }
-
-  mp_drop(m);
-  mp_drop(a);
-  mp_drop(b);
-  mp_drop(r);
-  mp_drop(mr);
-  mpbarrett_destroy(&mb);
-  assert(mparena_count(MPARENA_GLOBAL) == 0);
-  return ok;
-}
-
 static test_chunk tests[] = {
   { "mpbarrett-reduce", vmod, { &type_mp, &type_mp, &type_mp, 0 } },
-  { "mpbarrett-exp", vexp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
   { 0, 0, { 0 } }
 };