X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/b0ab12e6a6cb035df2b6312df7ad1736af0a6128..c65df27983057ec76ed0e72bb370f9a5ae7dad28:/f-prime.c

diff --git a/f-prime.c b/f-prime.c
index 1a7b9e8..f58bf63 100644
--- a/f-prime.c
+++ b/f-prime.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: f-prime.c,v 1.1 2001/04/29 18:12:33 mdw Exp $
+ * $Id: f-prime.c,v 1.12 2004/04/08 01:36:15 mdw Exp $
  *
  * Prime fields with Montgomery arithmetic
  *
@@ -27,125 +27,121 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: f-prime.c,v $
- * Revision 1.1  2001/04/29 18:12:33  mdw
- * Prototype version.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include <mLib/sub.h>
 
 #include "field.h"
 #include "mpmont.h"
+#include "mprand.h"
 
-/*----- Data structures ---------------------------------------------------*/
+/*----- Main code ---------------------------------------------------------*/
 
 typedef struct fctx {
   field f;
   mpmont mm;
 } fctx;
 
-/*----- Main code ---------------------------------------------------------*/
-
 /* --- Field operations --- */
 
 static void fdestroy(field *ff)
-{
-  fctx *f = (fctx *)ff;
-  mpmont_destroy(&f->mm);
-  DESTROY(f);
-}
+  { fctx *f = (fctx *)ff; mpmont_destroy(&f->mm); DESTROY(f); }
 
-static mp *fin(field *ff, mp *d, mp *x)
-{
+static mp *frand(field *ff, mp *d, grand *r)
+  { fctx *f = (fctx *)ff; return (mprand_range(d, f->mm.m, r, 0)); }
+
+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)
-{
-  fctx *f = (fctx *)ff;
-  return (mpmont_reduce(&f->mm, d, x));
-}
+  { fctx *f = (fctx *)ff; return (mpmont_reduce(&f->mm, d, x)); }
 
-static mp *fadd(field *ff, mp *d, mp *x, mp *y)
-{
-  return (mp_add(d, x, y));
+static int fzerop(field *ff, mp *x) { return (!MP_LEN(x)); }
+
+static mp *fneg(field *ff, mp *d, mp *x)
+  { fctx *f = (fctx *)ff; return (mp_sub(d, f->mm.m, x)); }
+
+static mp *fadd(field *ff, mp *d, mp *x, mp *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));
+static mp *fsub(field *ff, mp *d, mp *x, mp *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)
-{
-  fctx *f = (fctx *)ff;
-  return (mpmont_mul(&f->mm, d, x, y));
-}
+  { fctx *f = (fctx *)ff; return (mpmont_mul(&f->mm, d, x, y)); }
 
-static mp *fsqr(field *ff, mp *d, mp *x)
-{
-  fctx *f = (fctx *)ff;
-  d = mp_sqr(d, x);
+static mp *fsqr(field *ff, mp *d, mp *x) {
+  fctx *f = (fctx *)ff; d = mp_sqr(d, x);
   return (mpmont_reduce(&f->mm, d, d));
 }
 
-static mp *finv(field *ff, mp *d, mp *x)
-{
-  fctx *f = (fctx *)ff;
-  d = mpmont_reduce(&f->mm, x);
-  mp_gcd(0, 0, &d, f->mm.m, d);
-  return (mpmont_mul(&f->mm, d, d, f->mm.r2));
+static mp *finv(field *ff, mp *d, mp *x) {
+  fctx *f = (fctx *)ff; d = mpmont_reduce(&f->mm, d, x);
+  d = mp_modinv(d, d, f->mm.m); return (mpmont_mul(&f->mm, d, d, f->mm.r2));
 }
 
 static mp *freduce(field *ff, mp *d, mp *x)
-{
-  fctx *f = (fctx *)ff;
-  mp_div(0, &d, x, f->mm.m);
-  return (d);
+  { fctx *f = (fctx *)ff; mp_div(0, &d, x, f->mm.m); return (d); }
+
+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));
 }
 
-static mp *fdbl(field *ff, mp *d, mp *x)
-{
-  fctx *f = (fctx *)ff;
-  return (mp_lsl(d, x, 1));
+static mp *fdbl(field *ff, mp *d, mp *x) {
+  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;
-  MP_DEST(d, MP_LEN(x) + 1, x->f);
+static mp *ftpl(field *ff, mp *d, mp *x) {
+  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 *fsqrt(field *ff, mp *d, mp *x)
-{
+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;
-  d = mpmont_reduce(&f->mm, x);
-  d = mp_modsqrt(d, d, f->mm.m);
-  return (mpmont_mul(&f->mm, d, d, f->mm.r2));
+  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));
 }
 
 /* --- Field operations table --- */
 
-static field_ops fops = {
-  fdestroy,
+static const field_ops fops = {
+  FTY_PRIME, "prime",
+  fdestroy, frand, field_stdsamep,
   fin, fout,
-  fadd, fsub, fmul, fsqr, finv, freduce,
-  fdbl, ftpl, fsqrt
+  fzerop, fneg, fadd, fsub, fmul, fsqr, finv, freduce, fsqrt,
+  0,
+  fdbl, ftpl, fqdl, fhlv
 };
 
 /* --- @field_prime@ --- *
  *
  * Arguments:	@mp *p@ = the characteristic of the field
  *
- * Returns:	A pointer to the field.
+ * Returns:	A pointer to the field or null.
  *
  * Use:		Creates a field structure for a prime field of size %$p$%,
  *		using Montgomery reduction for arithmetic.
@@ -153,11 +149,18 @@ static field_ops fops = {
 
 field *field_prime(mp *p)
 {
-  ftcx *f = CREATE(fctx);
+  fctx *f;
+
+  if (!MP_ISPOS(p) || !MP_ISODD(p))
+    return (0);
+  f = CREATE(fctx);
   f->f.ops = &fops;
   mpmont_create(&f->mm, p);
-  f->zero = MP_ZERO;
-  f->one = &f->mm.r;
+  f->f.zero = MP_ZERO;
+  f->f.one = f->mm.r;
+  f->f.m = f->mm.m;
+  f->f.nbits = mp_bits(p);
+  f->f.noctets = (f->f.nbits + 7) >> 3;
   return (&f->f);
 }