X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/22bab86c9df047bdd258283c6567821319ba7a6f..2b645fb792c62ae0d38fcde4c39e1bd0889b0e06:/rabin.c

diff --git a/rabin.c b/rabin.c
index a5ebdcc..915dc14 100644
--- a/rabin.c
+++ b/rabin.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: rabin.c,v 1.5 2000/10/08 12:11:22 mdw Exp $
+ * $Id: rabin.c,v 1.7 2002/01/13 13:42:53 mdw Exp $
  *
  * Miller-Rabin primality test
  *
@@ -30,6 +30,13 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: rabin.c,v $
+ * Revision 1.7  2002/01/13 13:42:53  mdw
+ * More efficient Rabin-Miller test: with random witnesses, skip redundant
+ * Montgomerization.  (Being bijective, it can't affect the distribution.)
+ *
+ * Revision 1.6  2001/06/16 12:56:38  mdw
+ * Fixes for interface change to @mpmont_expr@ and @mpmont_mexpr@.
+ *
  * Revision 1.5  2000/10/08 12:11:22  mdw
  * Use @MP_EQ@ instead of @MP_CMP@.
  *
@@ -95,7 +102,7 @@ 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
@@ -104,10 +111,11 @@ 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;
@@ -153,6 +161,15 @@ 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