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

   1 /* -*-c-*-
   2  *
   3  * Binary fields with polynomial basis representation
   4  *
   5  * (c) 2004 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <mLib/sub.h>
  31
  32 #include "field.h"
  33 #include "field-guts.h"
  34 #include "mprand.h"
  35
  36 /*----- Polynomial basis --------------------------------------------------*/
  37
  38 /* --- Field operations --- */
  39
  40 static void fdestroy(field *ff) {
  41   fctx_binpoly *f = (fctx_binpoly *)ff;
  42   gfreduce_destroy(&f->r); MP_DROP(f->f.q);
  43   DESTROY(f);
  44 }
  45
  46 static mp *frand(field *f, mp *d, grand *r) {
  47   return (mprand(d, f->nbits, r, 0));
  48 }
  49
  50 static int fzerop(field *ff, mp *x) { return (MP_ZEROP(x)); }
  51
  52 static mp *fadd(field *ff, mp *d, mp *x, mp *y) { return (gf_add(d, x, y)); }
  53
  54 static mp *fmul(field *ff, mp *d, mp *x, mp *y) {
  55   fctx_binpoly *f = (fctx_binpoly *)ff; d = gf_mul(d, x, y);
  56   return (gfreduce_do(&f->r, d, d));
  57 }
  58
  59 static mp *fsqr(field *ff, mp *d, mp *x) {
  60   fctx_binpoly *f = (fctx_binpoly *)ff; d = gf_sqr(d, x);
  61   return (gfreduce_do(&f->r, d, d));
  62 }
  63
  64 static mp *finv(field *ff, mp *d, mp *x) {
  65   fctx_binpoly *f = (fctx_binpoly *)ff;
  66   d = gf_modinv(d, x, f->r.p);
  67   return (d);
  68 }
  69
  70 static mp *freduce(field *ff, mp *d, mp *x) {
  71   fctx_binpoly *f = (fctx_binpoly *)ff;
  72   return (gfreduce_do(&f->r, d, x));
  73 }
  74
  75 static mp *fsqrt(field *ff, mp *d, mp *x) {
  76   fctx_binpoly *f = (fctx_binpoly *)ff;
  77   return (gfreduce_sqrt(&f->r, d, x));
  78 }
  79
  80 static mp *fquadsolve(field *ff, mp *d, mp *x) {
  81   fctx_binpoly *f = (fctx_binpoly *)ff;
  82   return (gfreduce_quadsolve(&f->r, d, x));
  83 }
  84
  85 /* --- Field operations table --- */
  86
  87 static const field_ops fops = {
  88   FTY_BINARY, "binpoly",
  89   fdestroy, frand, field_stdsamep,
  90   freduce, field_id,
  91   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
  92   fquadsolve,
  93   0, 0, 0, 0
  94 };
  95
  96 /* --- @field_binpoly@ --- *
  97  *
  98  * Arguments:   @mp *p@ = the reduction polynomial
  99  *
 100  * Returns:     A pointer to the field.
 101  *
 102  * Use:         Creates a field structure for a binary field mod @p@.
 103  */
 104
 105 field *field_binpoly(mp *p)
 106 {
 107   fctx_binpoly *f = CREATE(fctx_binpoly);
 108   f->f.ops = &fops;
 109   f->f.zero = MP_ZERO;
 110   f->f.one = MP_ONE;
 111   f->f.nbits = mp_bits(p) - 1;
 112   f->f.noctets = (f->f.nbits + 7) >> 3;
 113   gfreduce_create(&f->r, p);
 114   f->f.m = f->r.p;
 115   f->f.q = mp_lsl(MP_NEW, MP_ONE, f->f.nbits);
 116   return (&f->f);
 117 }
 118
 119 /*----- Normal basis ------------------------------------------------------*/
 120
 121 /* --- Field operations --- */
 122
 123 static void fndestroy(field *ff) {
 124   fctx_binnorm *f = (fctx_binnorm *)ff; gfreduce_destroy(&f->f.r);
 125   gfn_destroy(&f->ntop); gfn_destroy(&f->pton); MP_DROP(f->f.f.q);
 126   DESTROY(f);
 127 }
 128
 129 static int fnsamep(field *ff, field *gg) {
 130   fctx_binnorm *f = (fctx_binnorm *)ff, *g = (fctx_binnorm *)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   fctx_binnorm *f = (fctx_binnorm *)ff;
 136   return (gfn_transform(&f->ntop, d, x));
 137 }
 138
 139 static mp *fnout(field *ff, mp *d, mp *x) {
 140   fctx_binnorm *f = (fctx_binnorm *)ff;
 141   return (gfn_transform(&f->pton, d, x));
 142 }
 143
 144 /* --- Field operations table --- */
 145
 146 static const field_ops fnops = {
 147   FTY_BINARY, "binnorm",
 148   fndestroy, frand, fnsamep,
 149   fnin, fnout,
 150   fzerop, field_id, fadd, fadd, fmul, fsqr, finv, freduce, fsqrt,
 151   fquadsolve,
 152   0, 0, 0, 0
 153 };
 154
 155 /* --- @field_binnorm@ --- *
 156  *
 157  * Arguments:   @mp *p@ = the reduction polynomial
 158  *              @mp *beta@ = representation of normal point
 159  *
 160  * Returns:     A pointer to the field.
 161  *
 162  * Use:         Creates a field structure for a binary field mod @p@ which
 163  *              uses a normal basis representation externally.  Computations
 164  *              are still done on a polynomial-basis representation.
 165  */
 166
 167 field *field_binnorm(mp *p, mp *beta)
 168 {
 169   fctx_binnorm *f = CREATE(fctx_binnorm);
 170   f->f.f.ops = &fnops;
 171   f->f.f.zero = MP_ZERO;
 172   f->f.f.one = MP_ONE;
 173   f->f.f.nbits = mp_bits(p) - 1;
 174   f->f.f.noctets = (f->f.f.nbits + 7) >> 3;
 175   gfreduce_create(&f->f.r, p);
 176   f->f.f.m = f->f.r.p;
 177   f->f.f.q = mp_lsl(MP_NEW, MP_ONE, f->f.f.nbits);
 178   gfn_create(p, beta, &f->ntop, &f->pton);
 179   return (&f->f.f);
 180 }
 181
 182 /*----- That's all, folks -------------------------------------------------*/