Merge branch 'master' of git.distorted.org.uk:~mdw/publish/public-git/catacomb

[u/mdw/catacomb] / rabin.c

diff --git a/rabin.c b/rabin.c
index 677e233..1b1130b 100644 (file)
--- a/rabin.c
+++ b/rabin.c
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: rabin.c,v 1.4 2000/06/22 19:03:02 mdw Exp $
+ * $Id$
  *
  * Miller-Rabin primality test
  *
  * (c) 1999 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Catacomb.
  *
@@ -15,36 +15,18 @@
  * 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: rabin.c,v $
- * Revision 1.4  2000/06/22 19:03:02  mdw
- * Use the new @mp_odd@ function.
- *
- * Revision 1.3  1999/12/22 15:50:29  mdw
- * Reworking for new prime-search system.  Add function for working out how
- * many iterations to use for a particular number.
- *
- * Revision 1.2  1999/12/10 23:29:48  mdw
- * Change header file guard names.
- *
- * Revision 1.1  1999/11/19 13:17:57  mdw
- * Prime number generator and tester.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "mp.h"
@@ -60,19 +42,23 @@
  * Arguments:  @rabin *r@ = pointer to Rabin-Miller context
  *             @mp *m@ = pointer to number to test
  *
- * Returns:    ---
+ * Returns:    Zero on success, nonzero on failure.
  *
  * Use:                Precomputes some useful values for performing the
  *             Miller-Rabin probabilistic primality test.
  */
 
-void rabin_create(rabin *r, mp *m)
+int rabin_create(rabin *r, mp *m)
 {
   mp *m1 = mp_sub(MP_NEW, m, MP_ONE);
-  mpmont_create(&r->mm, m);
+  if (mpmont_create(&r->mm, m)) {
+    MP_DROP(m1);
+    return (-1);
+  }
   r->r = mp_odd(MP_NEW, m1, &r->s);
   r->m1 = mp_sub(MP_NEW, m, r->mm.r);
   mp_drop(m1);
+  return (0);
 }
 
 /* --- @rabin_destroy@ --- *
@@ -92,7 +78,7 @@ void rabin_destroy(rabin *r)
   mpmont_destroy(&r->mm);
 }
 
-/* --- @rabin_test@ --- *
+/* --- @rabin_test@, @rabin_rtest@ --- *
  *
  * Arguments:  @rabin *r@ = pointer to Rabin-Miller context
  *             @mp *g@ = base to test the number against
@@ -101,10 +87,11 @@ void rabin_destroy(rabin *r)
  *             if it succeeded.
  *
  * Use:                Performs a single iteration of the Rabin-Miller primality
- *             test.
+ *             test.  The @rtest@ variant assumes that %$g$% is either
+ *             already in Montgomery representation, or you don't care.
  */
 
-int rabin_test(rabin *r, mp *g)
+int rabin_rtest(rabin *r, mp *g)
 {
   mp *y;
   mp *dd, *spare = MP_NEW;
@@ -118,7 +105,7 @@ int rabin_test(rabin *r, mp *g)
    */
 
   y = mpmont_expr(&r->mm, MP_NEW, g, r->r);
-  if (MP_CMP(y, ==, r->mm.r) || MP_CMP(y, ==, r->m1)) {
+  if (MP_EQ(y, r->mm.r) || MP_EQ(y, r->m1)) {
     rc = PGEN_PASS;
     goto done;
   }
@@ -133,9 +120,9 @@ int rabin_test(rabin *r, mp *g)
     dd = mp_sqr(spare, y);
     dd = mpmont_reduce(&r->mm, dd, dd);
     spare = y; y = dd;
-    if (MP_CMP(y, ==, r->mm.r))
+    if (MP_EQ(y, r->mm.r))
       break;
-    if (MP_CMP(y, ==, r->m1)) {
+    if (MP_EQ(y, r->m1)) {
       rc = PGEN_PASS;
       break;
     }
@@ -150,6 +137,15 @@ done:
   return (rc);
 }
 
+int rabin_test(rabin *r, mp *g)
+{
+  int rc;
+  g = mpmont_mul(&r->mm, MP_NEW, g, r->mm.r2);
+  rc = rabin_rtest(r, g);
+  mp_drop(g);
+  return (rc);
+}
+
 /* --- @rabin_iters@ --- *
  *
  * Arguments:  @unsigned len@ = number of bits in value
@@ -162,7 +158,7 @@ done:
 
 int rabin_iters(unsigned len)
 {
-  static struct {
+  static const struct {
     unsigned b;
     int i;
   } *p, *q, tab[] = {