From 41a324a748544b0fb9b0acfc65b1a39b7611550c Mon Sep 17 00:00:00 2001
From: mdw <mdw>
Date: Mon, 7 May 2001 17:29:44 +0000
Subject: [PATCH] Treat projective coordinates as an internal representation. 
 Various minor interface changes.

---
 ec.c | 100 +++++++++++++++++++++++++++++++++++++++++++++----------------------
 ec.h |  76 +++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 126 insertions(+), 50 deletions(-)

diff --git a/ec.c b/ec.c
index 604190b..37d8ad3 100644
--- a/ec.c
+++ b/ec.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: ec.c,v 1.1 2001/04/29 18:12:33 mdw Exp $
+ * $Id: ec.c,v 1.2 2001/05/07 17:29:44 mdw Exp $
  *
  * Elliptic curve definitions
  *
@@ -30,6 +30,10 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: ec.c,v $
+ * 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.
  *
@@ -97,21 +101,22 @@ void ec_setinf(ec *p) { EC_SETINF(p); }
 
 void ec_copy(ec *d, const ec *p) { EC_COPY(d, p); }
 
-/*----- Real arithmetic ---------------------------------------------------*/
+/*----- Standard curve operations -----------------------------------------*/
 
-/* --- @ec_denorm@ --- *
+/* --- @ec_idin@, @ec_idout@ --- *
  *
  * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
- *		@ec *d@ = pointer to the destination point
- *		@const ec *p@ = pointer to the source point
+ *		@ec *d@ = pointer to the destination
+ *		@const ec *p@ = pointer to a source point
  *
- * Returns:	---
+ * Returns:	The destination @d@.
  *
- * Use:		Denormalizes the given point, converting to internal
- *		representations and setting the denominator to 1.
+ * Use:		An identity operation if your curve has no internal
+ *		representation.  (The field internal representation is still
+ *		used.)
  */
 
-void ec_denorm(ec_curve *c, ec *d, const ec *p)
+ec *ec_idin(ec_curve *c, ec *d, const ec *p)
 {
   if (EC_ATINF(p))
     EC_SETINF(d);
@@ -119,24 +124,50 @@ void ec_denorm(ec_curve *c, ec *d, const ec *p)
     field *f = c->f;
     d->x = F_IN(f, d->x, p->x);
     d->y = F_IN(f, d->y, p->y);
-    mp_drop(d->z);
-    d->z = MP_COPY(f->one);
+    mp_drop(d->z); d->z = 0;
+  }
+  return (d);
+}
+
+ec *ec_idout(ec_curve *c, ec *d, const ec *p)
+{
+  if (EC_ATINF(p))
+    EC_SETINF(d);
+  else {
+    field *f = c->f;
+    d->x = F_OUT(f, d->x, p->x);
+    d->y = F_OUT(f, d->y, p->y);
+    mp_drop(d->z); d->z = 0;
   }
+  return (d);
 }
 
-/* --- @ec_norm@ --- *
+/* --- @ec_projin@, @ec_projout@ --- *
  *
  * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
- *		@ec *d@ = pointer to the destination point
- *		@const ec *p@ = pointer to the source point
+ *		@ec *d@ = pointer to the destination
+ *		@const ec *p@ = pointer to a source point
  *
- * Returns:	---
+ * Returns:	The destination @d@.
  *
- * Use:		Normalizes the given point, by dividing through by the
- *		denominator and returning to external representation.
+ * Use:		Conversion functions if your curve operations use a
+ *		projective representation.
  */
 
-void ec_norm(ec_curve *c, ec *d, const ec *p)
+ec *ec_projin(ec_curve *c, ec *d, const ec *p)
+{
+  if (EC_ATINF(p))
+    EC_SETINF(d);
+  else {
+    field *f = c->f;
+    d->x = F_IN(f, d->x, p->x);
+    d->y = F_IN(f, d->y, p->y);
+    mp_drop(d->z); d->z = MP_COPY(f->one);
+  }
+  return (d);
+}
+
+ec *ec_projout(ec_curve *c, ec *d, const ec *p)
 {
   if (EC_ATINF(p))
     EC_SETINF(d);
@@ -152,8 +183,11 @@ void ec_norm(ec_curve *c, ec *d, const ec *p)
     d->y = F_OUT(f, y, y);
     d->z = 0;
   }
+  return (d);
 }
 
+/*----- Real arithmetic ---------------------------------------------------*/
+
 /* --- @ec_find@ --- *
  *
  * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
@@ -165,14 +199,13 @@ void ec_norm(ec_curve *c, ec *d, const ec *p)
  * Use:		Finds a point on an elliptic curve with a given x-coordinate.
  */
 
-void ec_find(ec_curve *c, ec *d, mp *x)
+ec *ec_find(ec_curve *c, ec *d, mp *x)
 {
-  int rc;
   x = F_IN(c->f, MP_NEW, x);
-  if ((rc = EC_FIND(c, d, x)) == 0)
-    ec_norm(c, d, d);
+  if ((d = EC_FIND(c, d, x)) != 0)
+    EC_OUT(c, d, d);
   mp_drop(x);
-  return (rc);
+  return (d);
 }
 
 /* --- @ec_add@ --- *
@@ -186,15 +219,16 @@ void ec_find(ec_curve *c, ec *d, mp *x)
  * Use:		Adds two points on an elliptic curve.
  */
 
-void ec_add(ec_curve *c, ec *d, const ec *p, const ec *q)
+ec *ec_add(ec_curve *c, ec *d, const ec *p, const ec *q)
 {
   ec pp = EC_INIT, qq = EC_INIT;
-  ec_denorm(c, &pp, p);
-  ec_denorm(c, &qq, q);
+  EC_IN(c, &pp, p);
+  EC_IN(c, &qq, q);
   EC_ADD(c, d, &pp, &qq);
-  ec_norm(c, d, d);
+  EC_OUT(c, d, d);
   EC_DESTROY(&pp);
   EC_DESTROY(&qq);
+  return (d);
 }
 
 /* --- @ec_dbl@ --- *
@@ -208,11 +242,11 @@ void ec_add(ec_curve *c, ec *d, const ec *p, const ec *q)
  * Use:		Doubles a point on an elliptic curve.
  */
 
-void ec_dbl(ec_curve *c, ec *d, const ec *p)
+ec *ec_dbl(ec_curve *c, ec *d, const ec *p)
 {
-  ec_denorm(c, d, p);
+  EC_IN(c, d, p);
   EC_DBL(c, d, d);
-  ec_norm(c, d, d);
+  return (EC_OUT(c, d, d));
 }
 
 /* --- @ec_mul@ --- *
@@ -227,7 +261,7 @@ void ec_dbl(ec_curve *c, ec *d, const ec *p)
  * Use:		Multiplies a point by a scalar, returning %$n p$%.
  */
 
-void ec_mul(ec_curve *c, ec *d, const ec *p, mp *n)
+ec *ec_mul(ec_curve *c, ec *d, const ec *p, mp *n)
 {
   mpscan sc;
   ec g = EC_INIT;
@@ -243,7 +277,7 @@ void ec_mul(ec_curve *c, ec *d, const ec *p, mp *n)
   while (!MP_RBIT(&sc))
     MP_RSTEP(&sc);
 
-  ec_denorm(c, &g, p);
+  EC_IN(c, &g, p);
   if ((n->f & MP_BURN) && !(g.x->f & MP_BURN))
     MP_DEST(g.x, 0, MP_BURN);
   if ((n->f & MP_BURN) && !(g.y->f & MP_BURN))
@@ -274,7 +308,7 @@ done:
 
   EC_DESTROY(&g);
 exit:
-  ec_norm(c, d, d);
+  return (EC_OUT(c, d, d));
 }
 
 /*----- That's all, folks -------------------------------------------------*/
diff --git a/ec.h b/ec.h
index db5adfc..12ff823 100644
--- a/ec.h
+++ b/ec.h
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: ec.h,v 1.1 2001/04/29 18:12:33 mdw Exp $
+ * $Id: ec.h,v 1.2 2001/05/07 17:29:44 mdw Exp $
  *
  * Elliptic curve definitions
  *
@@ -30,6 +30,10 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: ec.h,v $
+ * 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.
  *
@@ -61,13 +65,18 @@ typedef struct ec {
 
 typedef struct ec_ops {
   void (*destroy)(ec_curve */*c*/);
-  int (*find)(ec_curve */*c*/, ec */*d*/, mp */*x*/);
-  void (*add)(ec_curve */*c*/, ec */*d*/, ec */*p*/, ec */*q*/);
-  void (*dbl)(ec_curve */*c*/, ec */*d*/, ec */*p*/);
+  ec *(*in)(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
+  ec *(*out)(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
+  ec *(*find)(ec_curve */*c*/, ec */*d*/, mp */*x*/);
+  ec *(*add)(ec_curve */*c*/, ec */*d*/, const ec */*p*/, const ec */*q*/);
+  ec *(*dbl)(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
 } ec_ops;
 
 #define EC_DESTROY(c)		(c)->ops->destroy((c))
 
+#define EC_IN(c, d, p)		(c)->ops->in((c), (d), (p))
+#define EC_OUT(c, d, p)		(c)->ops->in((c), (d), (p))
+
 #define EC_FIND(c, d, x)	(c)->ops->find((c), (d), (x))
 #define EC_ADD(c, d, p, q)	(c)->ops->add((c), (d), (p), (q))
 #define EC_DBL(c, d, p)		(c)->ops->dbl((c), (d), (p))
@@ -78,7 +87,7 @@ typedef struct ec_ops {
  *
  * Arguments:	@ec *p@ = pointer to an elliptic-curve point
  *
- * Returns:	---
+ * Returns:	The argument @p@.
  *
  * Use:		Initializes a new point.  The initial value is the additive
  *		identity (which is universal for all curves).
@@ -91,7 +100,7 @@ typedef struct ec_ops {
   _p->x = _p->y = _p->z = MP_NEW;					\
 } while (0)
 
-extern void ec_create(ec */*p*/);
+extern ec *ec_create(ec */*p*/);
 
 /* --- @ec_destroy@ --- *
  *
@@ -129,7 +138,7 @@ extern int ec_atinf(const ec */*p*/);
  *
  * Arguments:	@ec *p@ = pointer to a point
  *
- * Returns:	---
+ * Returns:	The argument @p@.
  *
  * Use:		Sets the given point to be the point %$O$% at infinity.
  */
@@ -146,14 +155,14 @@ extern int ec_atinf(const ec */*p*/);
   }									\
 } while (0)
 
-extern void ec_setinf(ec */*p*/);
+extern ec *ec_setinf(ec */*p*/);
 
 /* --- @ec_copy@ --- *
  *
  * Arguments:	@ec *d@ = pointer to destination point
  *		@const ec *p@ = pointer to source point
  *
- * Returns:	---
+ * Returns:	The destination @d@.
  *
  * Use:		Creates a copy of an elliptic curve point.
  */
@@ -173,7 +182,7 @@ extern void ec_setinf(ec */*p*/);
   }									\
 } while (0)
 
-extern void ec_copy(ec */*d*/, const ec */*p*/);
+extern ec *ec_copy(ec */*d*/, const ec */*p*/);
 
 /*----- Interesting arithmetic --------------------------------------------*/
 
@@ -224,13 +233,13 @@ extern void ec_find(ec_curve */*c*/, ec */*d*/, mp */*x*/);
  *		@ec *d@ = pointer to the destination point
  *		@const ec *p, *q@ = pointers to the operand points
  *
- * Returns:	---
+ * Returns:	The destination @d@.
  *
  * Use:		Adds two points on an elliptic curve.
  */
 
-extern void ec_add(ec_curve */*c*/, ec */*d*/,
-		   const ec */*p*/, const ec */*q*/);
+extern ec *ec_add(ec_curve */*c*/, ec */*d*/,
+		  const ec */*p*/, const ec */*q*/);
 
 /* --- @ec_dbl@ --- *
  *
@@ -238,12 +247,12 @@ extern void ec_add(ec_curve */*c*/, ec */*d*/,
  *		@ec *d@ = pointer to the destination point
  *		@const ec *p@ = pointer to the operand point
  *
- * Returns:	---
+ * Returns:	The destination @d@.
  *
  * Use:		Doubles a point on an elliptic curve.
  */
 
-extern void ec_dbl(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
+extern ec *ec_dbl(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
 
 /* --- @ec_mul@ --- *
  *
@@ -252,12 +261,45 @@ extern void ec_dbl(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
  *		@const ec *p@ = pointer to the generator point
  *		@mp *n@ = integer multiplier
  *
- * Returns:	---
+ * Returns:	The destination @d@.
  *
  * Use:		Multiplies a point by a scalar, returning %$n p$%.
  */
 
-extern void ec_mul(ec_curve */*c*/, ec */*d*/, const ec */*p*/, mp */*n*/);
+extern ec *ec_mul(ec_curve */*c*/, ec */*d*/, const ec */*p*/, mp */*n*/);
+
+/*----- Standard curve operations -----------------------------------------*/
+
+/* --- @ec_idin@, @ec_idout@ --- *
+ *
+ * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
+ *		@ec *d@ = pointer to the destination
+ *		@const ec *p@ = pointer to a source point
+ *
+ * Returns:	The destination @d@.
+ *
+ * Use:		An identity operation if your curve has no internal
+ *		representation.  (The field internal representation is still
+ *		used.)
+ */
+
+extern ec *ec_idin(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
+extern ec *ec_idout(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
+
+/* --- @ec_projin@, @ec_projout@ --- *
+ *
+ * Arguments:	@ec_curve *c@ = pointer to an elliptic curve
+ *		@ec *d@ = pointer to the destination
+ *		@const ec *p@ = pointer to a source point
+ *
+ * Returns:	The destination @d@.
+ *
+ * Use:		Conversion functions if your curve operations use a
+ *		projective representation.
+ */
+
+extern ec *ec_projin(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
+extern ec *ec_projout(ec_curve */*c*/, ec */*d*/, const ec */*p*/);
 
 /*----- Creating curves ---------------------------------------------------*/
 
-- 
2.11.0