X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/dbfee00a86609283c4633df870692be3db9bc5e4..02d7884df1f33c9c7dc3a14c4b1a5f520ebe090a:/f-prime.c

diff --git a/f-prime.c b/f-prime.c
index 0d76da0..43d6da3 100644
--- a/f-prime.c
+++ b/f-prime.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: f-prime.c,v 1.3.4.1 2003/06/10 13:43:53 mdw Exp $
+ * $Id: f-prime.c,v 1.11 2004/04/03 03:32:05 mdw Exp $
  *
  * Prime fields with Montgomery arithmetic
  *
@@ -30,6 +30,42 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: f-prime.c,v $
+ * Revision 1.11  2004/04/03 03:32:05  mdw
+ * General robustification.
+ *
+ * Revision 1.10  2004/04/02 01:03:49  mdw
+ * Miscellaneous constification.
+ *
+ * Revision 1.9  2004/04/01 21:28:41  mdw
+ * Normal basis support (translates to poly basis internally).  Rewrite
+ * EC and prime group table generators in awk, so that they can reuse data
+ * for repeated constants.
+ *
+ * Revision 1.8  2004/04/01 12:50:09  mdw
+ * Add cyclic group abstraction, with test code.  Separate off exponentation
+ * functions for better static linking.  Fix a buttload of bugs on the way.
+ * Generally ensure that negative exponents do inversion correctly.  Add
+ * table of standard prime-field subgroups.  (Binary field subgroups are
+ * currently unimplemented but easy to add if anyone ever finds a good one.)
+ *
+ * Revision 1.7  2004/03/27 17:54:11  mdw
+ * Standard curves and curve checking.
+ *
+ * Revision 1.6  2004/03/23 15:19:32  mdw
+ * Test elliptic curves more thoroughly.
+ *
+ * Revision 1.5  2004/03/23 12:08:26  mdw
+ * Random field-element selection.
+ *
+ * Revision 1.4  2004/03/21 22:52:06  mdw
+ * Merge and close elliptic curve branch.
+ *
+ * Revision 1.3.4.3  2004/03/21 22:39:46  mdw
+ * Elliptic curves on binary fields work.
+ *
+ * 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.
  *
@@ -50,135 +86,115 @@
 
 #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;
   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 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));
-}
+  { 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);
+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)
-{
-  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);
+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, d, 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);
+  mp_gcd(0, 0, &d, f->mm.m, d); 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;
-  d = mp_lsl(d, x, 1);
-  if (MP_CMP(d, >, f->mm.m))
-    d = mp_sub(d, d, f->mm.m);
+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);
+  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, d, 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,
-  fneg, 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.
@@ -186,11 +202,18 @@ static field_ops fops = {
 
 field *field_prime(mp *p)
 {
-  fctx *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->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);
 }