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

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