X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/8823192f6413bed15cfa884ed3a3cbbb97885657..c65df27983057ec76ed0e72bb370f9a5ae7dad28:/ec.c

diff --git a/ec.c b/ec.c
index a2b229f..a84dd7a 100644
--- a/ec.c
+++ b/ec.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: ec.c,v 1.4.4.2 2004/03/20 00:13:31 mdw Exp $
+ * $Id: ec.c,v 1.10 2004/04/08 01:36:15 mdw Exp $
  *
  * Elliptic curve definitions
  *
@@ -27,37 +27,28 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: ec.c,v $
- * Revision 1.4.4.2  2004/03/20 00:13:31  mdw
- * Projective coordinates for prime curves
- *
- * Revision 1.4.4.1  2003/06/10 13:43:53  mdw
- * Simple (non-projective) curves over prime fields now seem to work.
- *
- * Revision 1.4  2003/05/15 23:25:59  mdw
- * Make elliptic curve stuff build.
- *
- * Revision 1.3  2002/01/13 13:48:44  mdw
- * Further progress.
- *
- * Revision 1.2  2001/05/07 17:29:44  mdw
- * Treat projective coordinates as an internal representation.  Various
- * minor interface changes.
- *
- * Revision 1.1  2001/04/29 18:12:33  mdw
- * Prototype version.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "ec.h"
-#include "ec-exp.h"
 
 /*----- Trivial wrappers --------------------------------------------------*/
 
+/* --- @ec_samep@ --- *
+ *
+ * Arguments:	@ec_curve *c, *d@ = two elliptic curves
+ *
+ * Returns:	Nonzero if the curves are identical (not just isomorphic).
+ *
+ * Use:		Checks for sameness of curves.  This function does the full
+ *		check, not just the curve-type-specific check done by the
+ *		@sampep@ field operation.
+ */
+
+int ec_samep(ec_curve *c, ec_curve *d)
+{
+  return (field_samep(c->f, d->f) && c->ops == d->ops && EC_SAMEP(c, d));
+}
+
 /* --- @ec_create@ --- *
  *
  * Arguments:	@ec *p@ = pointer to an elliptic-curve point
@@ -114,8 +105,32 @@ ec *ec_setinf(ec *p) { EC_SETINF(p); return (p); }
 
 ec *ec_copy(ec *d, const ec *p) { EC_COPY(d, p); return (d); }
 
+/* --- @ec_eq@ --- *
+ *
+ * Arguments:	@const ec *p, *q@ = two points
+ *
+ * Returns:	Nonzero if the points are equal.  Compares external-format
+ *		points.
+ */
+
+int ec_eq(const ec *p, const ec *q) { return (EC_EQ(p, q)); }
+
 /*----- Standard curve operations -----------------------------------------*/
 
+/* --- @ec_stdsamep@ --- *
+ *
+ * Arguments:	@ec_curve *c, *d@ = two elliptic curves
+ *
+ * Returns:	Nonzero if the curves are identical (not just isomorphic).
+ *
+ * Use:		Simple sameness check on @a@ and @b@ curve members.
+ */
+
+int ec_stdsamep(ec_curve *c, ec_curve *d)
+{
+  return (MP_EQ(c->a, d->a) && MP_EQ(c->b, d->b));
+}
+
 /* --- @ec_idin@, @ec_idout@, @ec_idfix@ --- *
  *
  * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
@@ -161,7 +176,7 @@ ec *ec_idfix(ec_curve *c, ec *d, const ec *p)
   return (d);
 }
 
-/* --- @ec_projin@, @ec_projout@ --- *
+/* --- @ec_projin@, @ec_projout@, @ec_projfix@ --- *
  *
  * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
  *		@ec *d@ = pointer to the destination
@@ -227,7 +242,7 @@ ec *ec_projfix(ec_curve *c, ec *d, const ec *p)
     mp_drop(d->z);
     d->z = MP_COPY(f->one);
   }
-  return (d);  
+  return (d);
 }
 
 /* --- @ec_stdsub@ --- *
@@ -342,10 +357,10 @@ ec *ec_add(ec_curve *c, ec *d, const ec *p, const ec *q)
 
 ec *ec_sub(ec_curve *c, ec *d, const ec *p, const ec *q)
 {
-  ec pp, qq;
+  ec pp = EC_INIT, qq = EC_INIT;
   EC_IN(c, &pp, p);
   EC_IN(c, &qq, q);
-  EC_SUB(c, d, &qq, &qq);
+  EC_SUB(c, d, &pp, &qq);
   EC_OUT(c, d, d);
   EC_DESTROY(&pp);
   EC_DESTROY(&qq);
@@ -393,48 +408,24 @@ int ec_check(ec_curve *c, const ec *p)
   return (rc);
 }
 
-/* --- @ec_imul@, @ec_mul@ --- *
+/* --- @ec_rand@ --- *
  *
  * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
  *		@ec *d@ = pointer to the destination point
- *		@const ec *p@ = pointer to the generator point
- *		@mp *n@ = integer multiplier
+ *		@grand *r@ = random number source
  *
  * Returns:	The destination @d@.
  *
- * Use:		Multiplies a point by a scalar, returning %$n p$%.  The
- *		@imul@ variant uses internal representations for argument
- *		and result.
+ * Use:		Finds a random point on the given curve.
  */
 
-ec *ec_imul(ec_curve *c, ec *d, const ec *p, mp *n)
+ec *ec_rand(ec_curve *c, ec *d, grand *r)
 {
-  ec t = EC_INIT;
-
-  EC_COPY(&t, p);
-  if (t.x && (n->f & MP_BURN))
-    t.x->f |= MP_BURN;
-  MP_SHRINK(n);
-  EC_SETINF(d);
-  if (MP_LEN(n) == 0)
-    ;
-  else {
-    if (n->f & MP_NEG)
-      EC_NEG(c, &t, &t);
-    if (MP_LEN(n) < EXP_THRESH)
-      EXP_SIMPLE(*d, t, n);
-    else
-      EXP_WINDOW(*d, t, n);
-  }
-  EC_DESTROY(&t);
-  return (d);
-}
-
-ec *ec_mul(ec_curve *c, ec *d, const ec *p, mp *n)
-{
-  EC_IN(c, d, p);
-  ec_imul(c, d, d, n);
-  return (EC_OUT(c, d, d));
+  mp *x = MP_NEW;
+  do x = F_RAND(c->f, x, r); while (!EC_FIND(c, d, x));
+  mp_drop(x);
+  if (grand_range(r, 2)) EC_NEG(c, d, d);
+  return (EC_OUT(c, d, d));    
 }
 
 /*----- That's all, folks -------------------------------------------------*/