X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/432c4e184d44704511a5991b80224a87cb1d4613..298182ad446aaced14dea7ed0e7c968946787288:/ec-prime.c

diff --git a/ec-prime.c b/ec-prime.c
index ce81ba1..dc299fb 100644
--- a/ec-prime.c
+++ b/ec-prime.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: ec-prime.c,v 1.8 2004/03/27 17:54:11 mdw Exp $
+ * $Id$
  *
  * Elliptic curves over prime fields
  *
@@ -27,46 +27,6 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: ec-prime.c,v $
- * Revision 1.8  2004/03/27 17:54:11  mdw
- * Standard curves and curve checking.
- *
- * Revision 1.7  2004/03/27 00:04:46  mdw
- * Implement efficient reduction for pleasant-looking primes.
- *
- * Revision 1.6  2004/03/23 15:19:32  mdw
- * Test elliptic curves more thoroughly.
- *
- * Revision 1.5  2004/03/22 02:19:10  mdw
- * Rationalise the sliding-window threshold.  Drop guarantee that right
- * arguments to EC @add@ are canonical, and fix up projective implementations
- * to cope.
- *
- * Revision 1.4  2004/03/21 22:52:06  mdw
- * Merge and close elliptic curve branch.
- *
- * Revision 1.3.4.3  2004/03/21 22:39:46  mdw
- * Elliptic curves on binary fields work.
- *
- * Revision 1.3.4.2  2004/03/20 00:13:31  mdw
- * Projective coordinates for prime curves
- *
- * Revision 1.3.4.1  2003/06/10 13:43:53  mdw
- * Simple (non-projective) curves over prime fields now seem to work.
- *
- * Revision 1.3  2003/05/15 23:25:59  mdw
- * Make elliptic curve stuff build.
- *
- * Revision 1.2  2002/01/13 13:48:44  mdw
- * Further progress.
- *
- * Revision 1.1  2001/04/29 18:12:33  mdw
- * Prototype version.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include <mLib/sub.h>
@@ -108,10 +68,8 @@ static ec *ecfind(ec_curve *c, ec *d, mp *x)
 
 static ec *ecdbl(ec_curve *c, ec *d, const ec *a)
 {
-  if (EC_ATINF(a))
+  if (EC_ATINF(a) || F_ZEROP(c->f, a->y))
     EC_SETINF(d);
-  else if (F_ZEROP(c->f, a->y))
-    EC_COPY(d, a);
   else {
     field *f = c->f;
     mp *lambda;
@@ -142,10 +100,8 @@ static ec *ecdbl(ec_curve *c, ec *d, const ec *a)
 
 static ec *ecprojdbl(ec_curve *c, ec *d, const ec *a)
 {
-  if (EC_ATINF(a))
+  if (EC_ATINF(a) || F_ZEROP(c->f, a->y))
     EC_SETINF(d);
-  else if (F_ZEROP(c->f, a->y))
-    EC_COPY(d, a);
   else {
     field *f = c->f;
     mp *p, *q, *m, *s, *dx, *dy, *dz;
@@ -186,10 +142,8 @@ static ec *ecprojdbl(ec_curve *c, ec *d, const ec *a)
 
 static ec *ecprojxdbl(ec_curve *c, ec *d, const ec *a)
 {
-  if (EC_ATINF(a))
+  if (EC_ATINF(a) || F_ZEROP(c->f, a->y))
     EC_SETINF(d);
-  else if (F_ZEROP(c->f, a->y))
-    EC_COPY(d, a);
   else {
     field *f = c->f;
     mp *p, *q, *m, *s, *dx, *dy, *dz;
@@ -349,10 +303,12 @@ static ec *ecprojadd(ec_curve *c, ec *d, const ec *a, const ec *b)
 static int eccheck(ec_curve *c, const ec *p)
 {
   field *f = c->f;
+  mp *l, *x, *r;
   int rc;
-  mp *l = F_SQR(f, MP_NEW, p->y);
-  mp *x = F_SQR(f, MP_NEW, p->x);
-  mp *r = F_MUL(f, MP_NEW, x, p->x);
+  if (EC_ATINF(p)) return (0);
+  l = F_SQR(f, MP_NEW, p->y);
+  x = F_SQR(f, MP_NEW, p->x);
+  r = F_MUL(f, MP_NEW, x, p->x);
   x = F_MUL(f, x, c->a, p->x);
   r = F_ADD(f, r, r, x);
   r = F_ADD(f, r, r, c->b);
@@ -386,7 +342,7 @@ static void ecdestroy(ec_curve *c)
  * Arguments:	@field *f@ = the underlying field for this elliptic curve
  *		@mp *a, *b@ = the coefficients for this curve
  *
- * Returns:	A pointer to the curve.
+ * Returns:	A pointer to the curve, or null.
  *
  * Use:		Creates a curve structure for an elliptic curve defined over
  *		a prime field.  The @primeproj@ variant uses projective
@@ -422,17 +378,20 @@ extern ec_curve *ec_primeproj(field *f, mp *a, mp *b)
 }
 
 static const ec_ops ec_primeops = {
-  ecdestroy, ec_idin, ec_idout, ec_idfix,
+  "prime",
+  ecdestroy, ec_stdsamep, ec_idin, ec_idout, ec_idfix,
   ecfind, ecneg, ecadd, ec_stdsub, ecdbl, eccheck
 };
 
 static const ec_ops ec_primeprojops = {
-  ecdestroy, ec_projin, ec_projout, ec_projfix,
+  "primeproj",
+  ecdestroy, ec_stdsamep, ec_projin, ec_projout, ec_projfix,
   ecfind, ecneg, ecprojadd, ec_stdsub, ecprojdbl, ecprojcheck
 };
 
 static const ec_ops ec_primeprojxops = {
-  ecdestroy, ec_projin, ec_projout, ec_projfix,
+  "primeproj",
+  ecdestroy, ec_stdsamep, ec_projin, ec_projout, ec_projfix,
   ecfind, ecneg, ecprojadd, ec_stdsub, ecprojxdbl, ecprojcheck
 };