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

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