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

   1 /* -*-c-*-
   2  *
   3  * $Id: f-binpoly.c,v 1.1.2.1 2004/03/21 22:39:46 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 1.1.2.1  2004/03/21 22:39:46  mdw
  34  * Elliptic curves on binary fields work.
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 #include <mLib/sub.h>
  41
  42 #include "field.h"
  43 #include "gf.h"
  44 #include "gfreduce.h"
  45
  46 /*----- Data structures ---------------------------------------------------*/
  47
  48 typedef struct fctx {
  49   field f;
  50   gfreduce r;
  51 } fctx;
  52
  53 /*----- Main code ---------------------------------------------------------*/
  54
  55 /* --- Field operations --- */
  56
  57 static void fdestroy(field *ff)
  58 {
  59   fctx *f = (fctx *)ff;
  60   gfreduce_destroy(&f->r);
  61   DESTROY(f);
  62 }
  63
  64 static int fzerop(field *ff, mp *x)
  65 {
  66   return (!MP_LEN(x));
  67 }
  68
  69 static mp *fadd(field *ff, mp *d, mp *x, mp *y)
  70 {
  71   return (gf_add(d, x, y));
  72 }
  73
  74 static mp *fmul(field *ff, mp *d, mp *x, mp *y)
  75 {
  76   fctx *f = (fctx *)ff;
  77   d = gf_mul(d, x, y);
  78   return (gfreduce_do(&f->r, d, d));
  79 }
  80
  81 static mp *fsqr(field *ff, mp *d, mp *x)
  82 {
  83   fctx *f = (fctx *)ff;
  84   d = gf_sqr(d, x);
  85   return (gfreduce_do(&f->r, d, d));
  86 }
  87
  88 static mp *finv(field *ff, mp *d, mp *x)
  89 {
  90   fctx *f = (fctx *)ff;
  91   gf_gcd(0, 0, &d, f->r.p, x);
  92   return (d);
  93 }
  94
  95 static mp *freduce(field *ff, mp *d, mp *x)
  96 {
  97   fctx *f = (fctx *)ff;
  98   return (gfreduce_do(&f->r, d, x));
  99 }
 100
 101 static mp *fsqrt(field *ff, mp *d, mp *x)
 102 {
 103   fctx *f = (fctx *)ff;
 104   return (gfreduce_sqrt(&f->r, d, x));
 105 }
 106
 107 static mp *fquadsolve(field *ff, mp *d, mp *x)
 108 {
 109   fctx *f = (fctx *)ff;
 110   return (gfreduce_quadsolve(&f->r, d, x));
 111 }
 112
 113 /* --- Field operations table --- */
 114
 115 static field_ops fops = {
 116   fdestroy,
 117   freduce, field_id,
 118   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
 119   fquadsolve,
 120   0, 0, 0, 0
 121 };
 122
 123 /* --- @field_binpoly@ --- *
 124  *
 125  * Arguments:   @mp *p@ = the reduction polynomial
 126  *
 127  * Returns:     A pointer to the field.
 128  *
 129  * Use:         Creates a field structure for a binary field mod @p@.
 130  */
 131
 132 field *field_binpoly(mp *p)
 133 {
 134   fctx *f = CREATE(fctx);
 135   f->f.ops = &fops;
 136   f->f.zero = MP_ZERO;
 137   f->f.one = MP_ONE;
 138   gfreduce_create(&f->r, p);
 139   return (&f->f);
 140 }
 141
 142 /*----- That's all, folks -------------------------------------------------*/