X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/41cb1beba35c8a69ee7ae1298f51711995011b5c..8823192f6413bed15cfa884ed3a3cbbb97885657:/f-prime.c

diff --git a/f-prime.c b/f-prime.c
index f4bf3a7..7c1dae5 100644
--- a/f-prime.c
+++ b/f-prime.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: f-prime.c,v 1.3 2003/05/15 23:25:59 mdw Exp $
+ * $Id: f-prime.c,v 1.3.4.2 2004/03/20 00:13:31 mdw Exp $
  *
  * Prime fields with Montgomery arithmetic
  *
@@ -30,6 +30,12 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: f-prime.c,v $
+ * 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.
  *
@@ -69,7 +75,8 @@ static void fdestroy(field *ff)
 static mp *fin(field *ff, mp *d, mp *x)
 {
   fctx *f = (fctx *)ff;
-  return (mpmont_mul(&f->mm, d, x, f->mm.r2));
+  mp_div(0, &d, x, f->mm.m);
+  return (mpmont_mul(&f->mm, d, d, f->mm.r2));
 }
 
 static mp *fout(field *ff, mp *d, mp *x)
@@ -78,6 +85,11 @@ static mp *fout(field *ff, mp *d, mp *x)
   return (mpmont_reduce(&f->mm, d, x));
 }
 
+static int fzerop(field *ff, mp *x)
+{
+  return (!MP_LEN(x));
+}
+
 static mp *fneg(field *ff, mp *d, mp *x)
 {
   fctx *f = (fctx *)ff;
@@ -86,12 +98,24 @@ static mp *fneg(field *ff, mp *d, mp *x)
 
 static mp *fadd(field *ff, mp *d, mp *x, mp *y)
 {
-  return (mp_add(d, x, y));
+  fctx *f = (fctx *)ff;
+  d = mp_add(d, x, y);
+  if (d->f & MP_NEG)
+    d = mp_add(d, d, f->mm.m);
+  else if (MP_CMP(d, >, f->mm.m))
+    d = mp_sub(d, d, f->mm.m);
+  return (d);
 }
 
 static mp *fsub(field *ff, mp *d, mp *x, mp *y)
 {
-  return (mp_sub(d, x, y));
+  fctx *f = (fctx *)ff;
+  d = mp_sub(d, x, y);
+  if (d->f & MP_NEG)
+    d = mp_add(d, d, f->mm.m);
+  else if (MP_CMP(d, >, f->mm.m))
+    d = mp_sub(d, d, f->mm.m);
+  return (d);
 }
 
 static mp *fmul(field *ff, mp *d, mp *x, mp *y)
@@ -124,23 +148,54 @@ static mp *freduce(field *ff, mp *d, mp *x)
 
 static mp *fdbl(field *ff, mp *d, mp *x)
 {
-/*   fctx *f = (fctx *)ff; */
-  return (mp_lsl(d, x, 1));
+  fctx *f = (fctx *)ff;
+  d = mp_lsl(d, x, 1);
+  if (MP_CMP(d, >, f->mm.m))
+    d = mp_sub(d, d, f->mm.m);
+  return (d);
 }
 
 static mp *ftpl(field *ff, mp *d, mp *x)
 {
-/*   fctx *f = (fctx *)ff; */
+  fctx *f = (fctx *)ff;
   MP_DEST(d, MP_LEN(x) + 1, x->f);
   MPX_UMULN(d->v, d->vl, x->v, x->vl, 3);
+  while (MP_CMP(d, >, f->mm.m))
+    d = mp_sub(d, d, f->mm.m);
   return (d);
 }
 
+static mp *fqdl(field *ff, mp *d, mp *x)
+{
+  fctx *f = (fctx *)ff;
+  d = mp_lsl(d, x, 2);
+  while (MP_CMP(d, >, f->mm.m))
+    d = mp_sub(d, d, f->mm.m);
+  return (d);
+}
+
+static mp *fhlv(field *ff, mp *d, mp *x)
+{
+  fctx *f = (fctx *)ff;
+  if (!MP_LEN(x)) {
+    MP_COPY(x);
+    MP_DROP(d);
+    return (x);
+  }
+  if (x->v[0] & 1) {
+    d = mp_add(d, x, f->mm.m);
+    x = d;
+  }
+  return (mp_lsr(d, x, 1));
+}
+
 static mp *fsqrt(field *ff, mp *d, mp *x)
 {
   fctx *f = (fctx *)ff;
   d = mpmont_reduce(&f->mm, d, x);
   d = mp_modsqrt(d, d, f->mm.m);
+  if (!d)
+    return (d);
   return (mpmont_mul(&f->mm, d, d, f->mm.r2));
 }
 
@@ -149,8 +204,8 @@ static mp *fsqrt(field *ff, mp *d, mp *x)
 static field_ops fops = {
   fdestroy,
   fin, fout,
-  fneg, fadd, fsub, fmul, fsqr, finv, freduce,
-  fdbl, ftpl, fsqrt
+  fzerop, fneg, fadd, fsub, fmul, fsqr, finv, freduce,
+  fdbl, ftpl, fqdl, fhlv, fsqrt
 };
 
 /* --- @field_prime@ --- *