ec-bin (ec_binproj): Make curve setup faster.

[u/mdw/catacomb] / ec-bin.c

diff --git a/ec-bin.c b/ec-bin.c
index 30e19a9..e84252c 100644 (file)
--- a/ec-bin.c
+++ b/ec-bin.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: ec-bin.c,v 1.9 2004/04/08 01:36:15 mdw Exp $
+ * $Id$
  *
  * Arithmetic for elliptic curves over binary fields
  *
@@ -32,13 +32,7 @@
 #include <mLib/sub.h>
 
 #include "ec.h"
-
-/*----- Data structures ---------------------------------------------------*/
-
-typedef struct ecctx {
-  ec_curve c;
-  mp *bb;
-} ecctx;
+#include "ec-guts.h"
 
 /*----- Main code ---------------------------------------------------------*/
 
@@ -130,7 +124,7 @@ static ec *ecprojdbl(ec_curve *c, ec *d, const ec *a)
     EC_SETINF(d);
   else {
     field *f = c->f;
-    ecctx *cc = (ecctx *)c;
+    ecctx_bin *cc = (ecctx_bin *)c;
     mp *dx, *dy, *dz, *u, *v;
 
     dy = F_SQR(f, MP_NEW, a->z);       /* %$z^2$% */
@@ -326,7 +320,7 @@ static int ecprojcheck(ec_curve *c, const ec *p)
 
 static void ecdestroy(ec_curve *c)
 {
-  ecctx *cc = (ecctx *)c;
+  ecctx_bin *cc = (ecctx_bin *)c;
   MP_DROP(cc->c.a);
   MP_DROP(cc->c.b);
   if (cc->bb) MP_DROP(cc->bb);
@@ -347,7 +341,7 @@ static void ecdestroy(ec_curve *c)
 
 ec_curve *ec_bin(field *f, mp *a, mp *b)
 {
-  ecctx *cc = CREATE(ecctx);
+  ecctx_bin *cc = CREATE(ecctx_bin);
   cc->c.ops = &ec_binops;
   cc->c.f = f;
   cc->c.a = F_IN(f, MP_NEW, a);
@@ -358,29 +352,40 @@ ec_curve *ec_bin(field *f, mp *a, mp *b)
 
 ec_curve *ec_binproj(field *f, mp *a, mp *b)
 {
-  ecctx *cc = CREATE(ecctx);
+  ecctx_bin *cc = CREATE(ecctx_bin);
+  int i;
+  mp *c, *d;
+
   cc->c.ops = &ec_binprojops;
   cc->c.f = f;
   cc->c.a = F_IN(f, MP_NEW, a);
   cc->c.b = F_IN(f, MP_NEW, b);
-  cc->bb = F_SQRT(f, MP_NEW, cc->c.b);
-  if (cc->bb)
-    cc->bb = F_SQRT(f, cc->bb, cc->bb);
-  if (!cc->bb) {
+
+  c = MP_COPY(cc->c.b);
+  for (i = 0; i < f->nbits - 2; i++)
+    c = F_SQR(f, c, c);
+  d = F_SQR(f, MP_NEW, c); d = F_SQR(f, d, d);
+  if (!MP_EQ(d, cc->c.b)) {
+    MP_DROP(c);
+    MP_DROP(d);
     MP_DROP(cc->c.a);
     MP_DROP(cc->c.b);
     DESTROY(cc);
     return (0);
   }
+  cc->bb = c;
+  MP_DROP(d);
   return (&cc->c);
 }
 
 static const ec_ops ec_binops = {
+  "bin",
   ecdestroy, ec_stdsamep, ec_idin, ec_idout, ec_idfix,
   ecfind, ecneg, ecadd, ec_stdsub, ecdbl, eccheck
 };
 
 static const ec_ops ec_binprojops = {
+  "binproj",
   ecdestroy, ec_stdsamep, ec_projin, ec_projout, ec_projfix,
   ecfind, ecprojneg, ecprojadd, ec_stdsub, ecprojdbl, ecprojcheck
 };