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

   1 /* -*-c-*-
   2  *
   3  * $Id: f-binpoly.c,v 1.9 2004/04/08 01:36:15 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 /*----- Header files ------------------------------------------------------*/
  31
  32 #include <mLib/sub.h>
  33
  34 #include "field.h"
  35 #include "gf.h"
  36 #include "gfreduce.h"
  37 #include "mprand.h"
  38 #include "gfn.h"
  39
  40 /*----- Polynomial basis --------------------------------------------------*/
  41
  42 typedef struct fctx {
  43   field f;
  44   gfreduce r;
  45 } fctx;
  46
  47 /* --- Field operations --- */
  48
  49 static void fdestroy(field *ff)
  50   { fctx *f = (fctx *)ff; gfreduce_destroy(&f->r); DESTROY(f); }
  51
  52 static mp *frand(field *f, mp *d, grand *r)
  53   { return (mprand(d, f->nbits, r, 0)); }
  54
  55 static int fzerop(field *ff, mp *x) { return (!MP_LEN(x)); }
  56
  57 static mp *fadd(field *ff, mp *d, mp *x, mp *y) { return (gf_add(d, x, y)); }
  58
  59 static mp *fmul(field *ff, mp *d, mp *x, mp *y) {
  60   fctx *f = (fctx *)ff; d = gf_mul(d, x, y);
  61   return (gfreduce_do(&f->r, d, d));
  62 }
  63
  64 static mp *fsqr(field *ff, mp *d, mp *x) {
  65   fctx *f = (fctx *)ff; d = gf_sqr(d, x);
  66   return (gfreduce_do(&f->r, d, d));
  67 }
  68
  69 static mp *finv(field *ff, mp *d, mp *x)
  70   { fctx *f = (fctx *)ff; d = gf_modinv(d, x, f->r.p); return (d); }
  71
  72 static mp *freduce(field *ff, mp *d, mp *x)
  73   { fctx *f = (fctx *)ff; return (gfreduce_do(&f->r, d, x)); }
  74
  75 static mp *fsqrt(field *ff, mp *d, mp *x)
  76   { fctx *f = (fctx *)ff; return (gfreduce_sqrt(&f->r, d, x)); }
  77
  78 static mp *fquadsolve(field *ff, mp *d, mp *x)
  79   { fctx *f = (fctx *)ff; return (gfreduce_quadsolve(&f->r, d, x)); }
  80
  81 /* --- Field operations table --- */
  82
  83 static const field_ops fops = {
  84   FTY_BINARY, "binpoly",
  85   fdestroy, frand, field_stdsamep,
  86   freduce, field_id,
  87   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
  88   fquadsolve,
  89   0, 0, 0, 0
  90 };
  91
  92 /* --- @field_binpoly@ --- *
  93  *
  94  * Arguments:   @mp *p@ = the reduction polynomial
  95  *
  96  * Returns:     A pointer to the field.
  97  *
  98  * Use:         Creates a field structure for a binary field mod @p@.
  99  */
 100
 101 field *field_binpoly(mp *p)
 102 {
 103   fctx *f = CREATE(fctx);
 104   f->f.ops = &fops;
 105   f->f.zero = MP_ZERO;
 106   f->f.one = MP_ONE;
 107   f->f.nbits = mp_bits(p) - 1;
 108   f->f.noctets = (f->f.nbits + 7) >> 3;
 109   gfreduce_create(&f->r, p);
 110   f->f.m = f->r.p;
 111   return (&f->f);
 112 }
 113
 114 /*----- Normal basis ------------------------------------------------------*/
 115
 116 typedef struct fnctx {
 117   fctx f;
 118   gfn ntop, pton;
 119 } fnctx;
 120
 121 /* --- Field operations --- */
 122
 123 static void fndestroy(field *ff) {
 124   fnctx *f = (fnctx *)ff; gfreduce_destroy(&f->f.r);
 125   gfn_destroy(&f->ntop); gfn_destroy(&f->pton);
 126   DESTROY(f);
 127 }
 128
 129 static int fnsamep(field *ff, field *gg) {
 130   fnctx *f = (fnctx *)ff, *g = (fnctx *)gg;
 131   return (MP_EQ(f->ntop.r[0], g->ntop.r[0]) && field_stdsamep(ff, gg));
 132 }
 133
 134 static mp *fnin(field *ff, mp *d, mp *x)
 135   { fnctx *f = (fnctx *)ff; return (gfn_transform(&f->ntop, d, x)); }
 136
 137 static mp *fnout(field *ff, mp *d, mp *x)
 138   { fnctx *f = (fnctx *)ff; return (gfn_transform(&f->pton, d, x)); }
 139
 140 /* --- Field operations table --- */
 141
 142 static const field_ops fnops = {
 143   FTY_BINARY, "binnorm",
 144   fndestroy, frand, fnsamep,
 145   fnin, fnout,
 146   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
 147   fquadsolve,
 148   0, 0, 0, 0
 149 };
 150
 151 /* --- @field_binnorm@ --- *
 152  *
 153  * Arguments:   @mp *p@ = the reduction polynomial
 154  *              @mp *beta@ = representation of normal point
 155  *
 156  * Returns:     A pointer to the field.
 157  *
 158  * Use:         Creates a field structure for a binary field mod @p@ which
 159  *              uses a normal basis representation externally.  Computations
 160  *              are still done on a polynomial-basis representation.
 161  */
 162
 163 field *field_binnorm(mp *p, mp *beta)
 164 {
 165   fnctx *f = CREATE(fnctx);
 166   f->f.f.ops = &fnops;
 167   f->f.f.zero = MP_ZERO;
 168   f->f.f.one = MP_ONE;
 169   f->f.f.nbits = mp_bits(p) - 1;
 170   f->f.f.noctets = (f->f.f.nbits + 7) >> 3;
 171   gfreduce_create(&f->f.r, p);
 172   f->f.f.m = f->f.r.p;
 173   gfn_create(p, beta, &f->ntop, &f->pton);
 174   return (&f->f.f);
 175 }
 176
 177 /*----- That's all, folks -------------------------------------------------*/