Keep numbers positive.

[u/mdw/catacomb] / calc / ecp.cal

diff --git a/calc/ecp.cal b/calc/ecp.cal
index 82600f5..10ed9e4 100644 (file)
--- a/calc/ecp.cal
+++ b/calc/ecp.cal
@@ -1,6 +1,6 @@
 /* -*-apcalc-*-
  *
- * $Id: ecp.cal,v 1.1.4.1 2003/06/10 13:43:53 mdw Exp $
+ * $Id: ecp.cal,v 1.4 2004/04/01 13:37:07 mdw Exp $
  *
  * Testbed for elliptic curve arithmetic over prime fields
  *
@@ -30,6 +30,18 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: ecp.cal,v $
+ * Revision 1.4  2004/04/01 13:37:07  mdw
+ * Keep numbers positive.
+ *
+ * Revision 1.3  2004/03/23 15:19:32  mdw
+ * Test elliptic curves more thoroughly.
+ *
+ * Revision 1.2  2004/03/21 22:52:06  mdw
+ * Merge and close elliptic curve branch.
+ *
+ * Revision 1.1.4.2  2004/03/20 00:13:31  mdw
+ * Projective coordinates for prime curves
+ *
  * Revision 1.1.4.1  2003/06/10 13:43:53  mdw
  * Simple (non-projective) curves over prime fields now seem to work.
  *
@@ -103,6 +115,8 @@ define ecp_pt_dbl(a)
 {
   local e, alpha;
   local obj ecp_pt d;
+  if (istype(a, 1))
+    return (0);
   e = a.e;
   alpha = (3 * a.x^2 + e.a) * minv(2 * a.y, e.p) % e.p;
   d.x = (alpha^2 - 2 * a.x) % e.p;
@@ -115,7 +129,7 @@ define ecp_pt_neg(a)
 {
   local obj ecp_pt d;
   d.x = a.x;
-  d.y = -a.y;
+  d.y = a.e.p - a.y;
   d.e = a.e;
   return (d);
 }