git.distorted.org.uk Git - u/mdw/catacomb/blob - f-binpoly.c

   1 /* -*-c-*-
   2  *
   3  * $Id: f-binpoly.c,v 1.6 2004/04/01 12:50:09 mdw Exp $
   4  *
   5  * Binary fields with polynomial basis representation
   6  *
   7  * (c) 2004 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: f-binpoly.c,v $
  33  * Revision 1.6  2004/04/01 12:50:09  mdw
  34  * Add cyclic group abstraction, with test code.  Separate off exponentation
  35  * functions for better static linking.  Fix a buttload of bugs on the way.
  36  * Generally ensure that negative exponents do inversion correctly.  Add
  37  * table of standard prime-field subgroups.  (Binary field subgroups are
  38  * currently unimplemented but easy to add if anyone ever finds a good one.)
  39  *
  40  * Revision 1.5  2004/03/27 17:54:11  mdw
  41  * Standard curves and curve checking.
  42  *
  43  * Revision 1.4  2004/03/23 15:19:32  mdw
  44  * Test elliptic curves more thoroughly.
  45  *
  46  * Revision 1.3  2004/03/23 12:08:26  mdw
  47  * Random field-element selection.
  48  *
  49  * Revision 1.2  2004/03/21 22:52:06  mdw
  50  * Merge and close elliptic curve branch.
  51  *
  52  * Revision 1.1.2.1  2004/03/21 22:39:46  mdw
  53  * Elliptic curves on binary fields work.
  54  *
  55  */
  56
  57 /*----- Header files ------------------------------------------------------*/
  58
  59 #include <mLib/sub.h>
  60
  61 #include "field.h"
  62 #include "gf.h"
  63 #include "gfreduce.h"
  64 #include "mprand.h"
  65
  66 /*----- Data structures ---------------------------------------------------*/
  67
  68 typedef struct fctx {
  69   field f;
  70   gfreduce r;
  71 } fctx;
  72
  73 /*----- Main code ---------------------------------------------------------*/
  74
  75 /* --- Field operations --- */
  76
  77 static void fdestroy(field *ff)
  78 {
  79   fctx *f = (fctx *)ff;
  80   gfreduce_destroy(&f->r);
  81   DESTROY(f);
  82 }
  83
  84 static mp *frand(field *f, mp *d, grand *r)
  85 {
  86   return (mprand(d, f->nbits, r, 0));
  87 }
  88
  89 static int fzerop(field *ff, mp *x)
  90 {
  91   return (!MP_LEN(x));
  92 }
  93
  94 static mp *fadd(field *ff, mp *d, mp *x, mp *y)
  95 {
  96   return (gf_add(d, x, y));
  97 }
  98
  99 static mp *fmul(field *ff, mp *d, mp *x, mp *y)
 100 {
 101   fctx *f = (fctx *)ff;
 102   d = gf_mul(d, x, y);
 103   return (gfreduce_do(&f->r, d, d));
 104 }
 105
 106 static mp *fsqr(field *ff, mp *d, mp *x)
 107 {
 108   fctx *f = (fctx *)ff;
 109   d = gf_sqr(d, x);
 110   return (gfreduce_do(&f->r, d, d));
 111 }
 112
 113 static mp *finv(field *ff, mp *d, mp *x)
 114 {
 115   fctx *f = (fctx *)ff;
 116   gf_gcd(0, 0, &d, f->r.p, x);
 117   return (d);
 118 }
 119
 120 static mp *freduce(field *ff, mp *d, mp *x)
 121 {
 122   fctx *f = (fctx *)ff;
 123   return (gfreduce_do(&f->r, d, x));
 124 }
 125
 126 static mp *fsqrt(field *ff, mp *d, mp *x)
 127 {
 128   fctx *f = (fctx *)ff;
 129   return (gfreduce_sqrt(&f->r, d, x));
 130 }
 131
 132 static mp *fquadsolve(field *ff, mp *d, mp *x)
 133 {
 134   fctx *f = (fctx *)ff;
 135   return (gfreduce_quadsolve(&f->r, d, x));
 136 }
 137
 138 /* --- Field operations table --- */
 139
 140 static field_ops fops = {
 141   FTY_BINARY, "binpoly",
 142   fdestroy, frand, field_stdsamep,
 143   freduce, field_id,
 144   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
 145   fquadsolve,
 146   0, 0, 0, 0
 147 };
 148
 149 /* --- @field_binpoly@ --- *
 150  *
 151  * Arguments:   @mp *p@ = the reduction polynomial
 152  *
 153  * Returns:     A pointer to the field.
 154  *
 155  * Use:         Creates a field structure for a binary field mod @p@.
 156  */
 157
 158 field *field_binpoly(mp *p)
 159 {
 160   fctx *f = CREATE(fctx);
 161   f->f.ops = &fops;
 162   f->f.zero = MP_ZERO;
 163   f->f.one = MP_ONE;
 164   f->f.nbits = mp_bits(p) - 1;
 165   f->f.noctets = (f->f.nbits + 7) >> 3;
 166   gfreduce_create(&f->r, p);
 167   f->f.m = f->r.p;
 168   return (&f->f);
 169 }
 170
 171 /*----- That's all, folks -------------------------------------------------*/