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

   1 /* -*-c-*-
   2  *
   3  * $Id: f-binpoly.c,v 1.5 2004/03/27 17:54:11 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 1.5  2004/03/27 17:54:11  mdw
  34  * Standard curves and curve checking.
  35  *
  36  * Revision 1.4  2004/03/23 15:19:32  mdw
  37  * Test elliptic curves more thoroughly.
  38  *
  39  * Revision 1.3  2004/03/23 12:08:26  mdw
  40  * Random field-element selection.
  41  *
  42  * Revision 1.2  2004/03/21 22:52:06  mdw
  43  * Merge and close elliptic curve branch.
  44  *
  45  * Revision 1.1.2.1  2004/03/21 22:39:46  mdw
  46  * Elliptic curves on binary fields work.
  47  *
  48  */
  49
  50 /*----- Header files ------------------------------------------------------*/
  51
  52 #include <mLib/sub.h>
  53
  54 #include "field.h"
  55 #include "gf.h"
  56 #include "gfreduce.h"
  57 #include "mprand.h"
  58
  59 /*----- Data structures ---------------------------------------------------*/
  60
  61 typedef struct fctx {
  62   field f;
  63   gfreduce r;
  64 } fctx;
  65
  66 /*----- Main code ---------------------------------------------------------*/
  67
  68 /* --- Field operations --- */
  69
  70 static void fdestroy(field *ff)
  71 {
  72   fctx *f = (fctx *)ff;
  73   gfreduce_destroy(&f->r);
  74   DESTROY(f);
  75 }
  76
  77 static mp *frand(field *f, mp *d, grand *r)
  78 {
  79   return (mprand(d, f->nbits, r, 0));
  80 }
  81
  82 static int fzerop(field *ff, mp *x)
  83 {
  84   return (!MP_LEN(x));
  85 }
  86
  87 static mp *fadd(field *ff, mp *d, mp *x, mp *y)
  88 {
  89   return (gf_add(d, x, y));
  90 }
  91
  92 static mp *fmul(field *ff, mp *d, mp *x, mp *y)
  93 {
  94   fctx *f = (fctx *)ff;
  95   d = gf_mul(d, x, y);
  96   return (gfreduce_do(&f->r, d, d));
  97 }
  98
  99 static mp *fsqr(field *ff, mp *d, mp *x)
 100 {
 101   fctx *f = (fctx *)ff;
 102   d = gf_sqr(d, x);
 103   return (gfreduce_do(&f->r, d, d));
 104 }
 105
 106 static mp *finv(field *ff, mp *d, mp *x)
 107 {
 108   fctx *f = (fctx *)ff;
 109   gf_gcd(0, 0, &d, f->r.p, x);
 110   return (d);
 111 }
 112
 113 static mp *freduce(field *ff, mp *d, mp *x)
 114 {
 115   fctx *f = (fctx *)ff;
 116   return (gfreduce_do(&f->r, d, x));
 117 }
 118
 119 static mp *fsqrt(field *ff, mp *d, mp *x)
 120 {
 121   fctx *f = (fctx *)ff;
 122   return (gfreduce_sqrt(&f->r, d, x));
 123 }
 124
 125 static mp *fquadsolve(field *ff, mp *d, mp *x)
 126 {
 127   fctx *f = (fctx *)ff;
 128   return (gfreduce_quadsolve(&f->r, d, x));
 129 }
 130
 131 /* --- Field operations table --- */
 132
 133 static field_ops fops = {
 134   FTY_BINARY, "binpoly",
 135   fdestroy, frand,
 136   freduce, field_id,
 137   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
 138   fquadsolve,
 139   0, 0, 0, 0
 140 };
 141
 142 /* --- @field_binpoly@ --- *
 143  *
 144  * Arguments:   @mp *p@ = the reduction polynomial
 145  *
 146  * Returns:     A pointer to the field.
 147  *
 148  * Use:         Creates a field structure for a binary field mod @p@.
 149  */
 150
 151 field *field_binpoly(mp *p)
 152 {
 153   fctx *f = CREATE(fctx);
 154   f->f.ops = &fops;
 155   f->f.zero = MP_ZERO;
 156   f->f.one = MP_ONE;
 157   f->f.nbits = mp_bits(p) - 1;
 158   f->f.noctets = (f->f.nbits + 7) >> 3;
 159   gfreduce_create(&f->r, p);
 160   f->f.m = f->r.p;
 161   return (&f->f);
 162 }
 163
 164 /*----- That's all, folks -------------------------------------------------*/