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

   1 /* -*-c-*-
   2  *
   3  * $Id$
   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 "field-guts.h"
  36 #include "mprand.h"
  37
  38 /*----- Polynomial basis --------------------------------------------------*/
  39
  40 /* --- Field operations --- */
  41
  42 static void fdestroy(field *ff) {
  43   fctx_binpoly *f = (fctx_binpoly *)ff;
  44   gfreduce_destroy(&f->r); MP_DROP(f->f.q);
  45   DESTROY(f);
  46 }
  47
  48 static mp *frand(field *f, mp *d, grand *r) {
  49   return (mprand(d, f->nbits, r, 0));
  50 }
  51
  52 static int fzerop(field *ff, mp *x) { return (MP_ZEROP(x)); }
  53
  54 static mp *fadd(field *ff, mp *d, mp *x, mp *y) { return (gf_add(d, x, y)); }
  55
  56 static mp *fmul(field *ff, mp *d, mp *x, mp *y) {
  57   fctx_binpoly *f = (fctx_binpoly *)ff; d = gf_mul(d, x, y);
  58   return (gfreduce_do(&f->r, d, d));
  59 }
  60
  61 static mp *fsqr(field *ff, mp *d, mp *x) {
  62   fctx_binpoly *f = (fctx_binpoly *)ff; d = gf_sqr(d, x);
  63   return (gfreduce_do(&f->r, d, d));
  64 }
  65
  66 static mp *finv(field *ff, mp *d, mp *x) {
  67   fctx_binpoly *f = (fctx_binpoly *)ff;
  68   d = gf_modinv(d, x, f->r.p);
  69   return (d);
  70 }
  71
  72 static mp *freduce(field *ff, mp *d, mp *x) {
  73   fctx_binpoly *f = (fctx_binpoly *)ff;
  74   return (gfreduce_do(&f->r, d, x));
  75 }
  76
  77 static mp *fsqrt(field *ff, mp *d, mp *x) {
  78   fctx_binpoly *f = (fctx_binpoly *)ff;
  79   return (gfreduce_sqrt(&f->r, d, x));
  80 }
  81
  82 static mp *fquadsolve(field *ff, mp *d, mp *x) {
  83   fctx_binpoly *f = (fctx_binpoly *)ff;
  84   return (gfreduce_quadsolve(&f->r, d, x));
  85 }
  86
  87 /* --- Field operations table --- */
  88
  89 static const field_ops fops = {
  90   FTY_BINARY, "binpoly",
  91   fdestroy, frand, field_stdsamep,
  92   freduce, field_id,
  93   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
  94   fquadsolve,
  95   0, 0, 0, 0
  96 };
  97
  98 /* --- @field_binpoly@ --- *
  99  *
 100  * Arguments:   @mp *p@ = the reduction polynomial
 101  *
 102  * Returns:     A pointer to the field.
 103  *
 104  * Use:         Creates a field structure for a binary field mod @p@.
 105  */
 106
 107 field *field_binpoly(mp *p)
 108 {
 109   fctx_binpoly *f = CREATE(fctx_binpoly);
 110   f->f.ops = &fops;
 111   f->f.zero = MP_ZERO;
 112   f->f.one = MP_ONE;
 113   f->f.nbits = mp_bits(p) - 1;
 114   f->f.noctets = (f->f.nbits + 7) >> 3;
 115   gfreduce_create(&f->r, p);
 116   f->f.m = f->r.p;
 117   f->f.q = mp_lsl(MP_NEW, MP_ONE, f->f.nbits);
 118   return (&f->f);
 119 }
 120
 121 /*----- Normal basis ------------------------------------------------------*/
 122
 123 /* --- Field operations --- */
 124
 125 static void fndestroy(field *ff) {
 126   fctx_binnorm *f = (fctx_binnorm *)ff; gfreduce_destroy(&f->f.r);
 127   gfn_destroy(&f->ntop); gfn_destroy(&f->pton); MP_DROP(f->f.f.q);
 128   DESTROY(f);
 129 }
 130
 131 static int fnsamep(field *ff, field *gg) {
 132   fctx_binnorm *f = (fctx_binnorm *)ff, *g = (fctx_binnorm *)gg;
 133   return (MP_EQ(f->ntop.r[0], g->ntop.r[0]) && field_stdsamep(ff, gg));
 134 }
 135
 136 static mp *fnin(field *ff, mp *d, mp *x) {
 137   fctx_binnorm *f = (fctx_binnorm *)ff;
 138   return (gfn_transform(&f->ntop, d, x));
 139 }
 140
 141 static mp *fnout(field *ff, mp *d, mp *x) {
 142   fctx_binnorm *f = (fctx_binnorm *)ff;
 143   return (gfn_transform(&f->pton, d, x));
 144 }
 145
 146 /* --- Field operations table --- */
 147
 148 static const field_ops fnops = {
 149   FTY_BINARY, "binnorm",
 150   fndestroy, frand, fnsamep,
 151   fnin, fnout,
 152   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
 153   fquadsolve,
 154   0, 0, 0, 0
 155 };
 156
 157 /* --- @field_binnorm@ --- *
 158  *
 159  * Arguments:   @mp *p@ = the reduction polynomial
 160  *              @mp *beta@ = representation of normal point
 161  *
 162  * Returns:     A pointer to the field.
 163  *
 164  * Use:         Creates a field structure for a binary field mod @p@ which
 165  *              uses a normal basis representation externally.  Computations
 166  *              are still done on a polynomial-basis representation.
 167  */
 168
 169 field *field_binnorm(mp *p, mp *beta)
 170 {
 171   fctx_binnorm *f = CREATE(fctx_binnorm);
 172   f->f.f.ops = &fnops;
 173   f->f.f.zero = MP_ZERO;
 174   f->f.f.one = MP_ONE;
 175   f->f.f.nbits = mp_bits(p) - 1;
 176   f->f.f.noctets = (f->f.f.nbits + 7) >> 3;
 177   gfreduce_create(&f->f.r, p);
 178   f->f.f.m = f->f.r.p;
 179   f->f.f.q = mp_lsl(MP_NEW, MP_ONE, f->f.f.nbits);
 180   gfn_create(p, beta, &f->ntop, &f->pton);
 181   return (&f->f.f);
 182 }
 183
 184 /*----- That's all, folks -------------------------------------------------*/