mdw@git.distorted.org.uk Git - catacomb/blob - math/g-bin.c

   1 /* -*-c-*-
   2  *
   3  * Abstraction for prime groups
   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 "mpmont.h"
  33 #include "pgen.h"
  34
  35 #define ge ge_bin
  36 #include "group-guts.h"
  37
  38 /*----- Main code ---------------------------------------------------------*/
  39
  40 /* --- Group operations --- */
  41
  42 static void gdestroygroup(group *gg) {
  43   gctx_bin *g = (gctx_bin *)gg;
  44   mp_drop(g->gen.x); mp_drop(g->g.r); mp_drop(g->g.h);
  45   gfreduce_destroy(&g->r);
  46   DESTROY(g);
  47 }
  48
  49 static ge_bin *gcreate(group *gg) {
  50   gctx_bin *g = (gctx_bin *)gg; ge_bin *x = CREATE(ge_bin);
  51   x->x = MP_COPY(g->one.x); return (x);
  52 }
  53
  54 static void gcopy(group *gg, ge_bin *d, ge_bin *x)
  55   { mp *t = MP_COPY(x->x); MP_DROP(d->x); d->x = t; }
  56
  57 static void gburn(group *gg, ge_bin *x) { x->x->f |= MP_BURN; }
  58
  59 static void gdestroy(group *gg, ge_bin *x) { MP_DROP(x->x); DESTROY(x); }
  60
  61 static int gsamep(group *gg, group *hh) {
  62   gctx_bin *g = (gctx_bin *)gg, *h = (gctx_bin *)hh;
  63   return (MP_EQ(g->r.p, h->r.p));
  64 }
  65
  66 static int geq(group *gg, ge_bin *x, ge_bin *y)
  67   { return (MP_EQ(x->x, y->x)); }
  68
  69 static const char *gcheck(group *gg, grand *gr) {
  70   gctx_bin *g = (gctx_bin *)gg; int rc; mp *t, *tt;
  71   if (!gf_irreduciblep(g->r.p)) return ("p is not irreducible");
  72   t = mp_mul(MP_NEW, g->g.r, g->g.h); t = mp_add(t, t, MP_ONE);
  73   tt = mp_lsl(MP_NEW, MP_ONE, g->g.nbits);
  74   rc = MP_EQ(t, tt); MP_DROP(t); MP_DROP(tt);
  75   if (!rc) return ("not a subgroup");
  76   return (group_stdcheck(gg, gr));
  77 }
  78
  79 static void gmul(group *gg, ge_bin *d, ge_bin *x, ge_bin *y) {
  80   gctx_bin *g = (gctx_bin *)gg; mp *r = gf_mul(d->x, x->x, y->x);
  81   d->x = gfreduce_do(&g->r, r, r);
  82 }
  83
  84 static void gsqr(group *gg, ge_bin *d, ge_bin *x) {
  85   gctx_bin *g = (gctx_bin *)gg; mp *r = gf_sqr(d->x, x->x);
  86   d->x = gfreduce_do(&g->r, r, r);
  87 }
  88
  89 static void ginv(group *gg, ge_bin *d, ge_bin *x)
  90   { gctx_bin *g = (gctx_bin *)gg; d->x = gf_modinv(d->x, x->x, g->r.p); }
  91
  92 static void gexp(group *gg, ge_bin *d, ge_bin *x, mp *n) {
  93   gctx_bin *g = (gctx_bin *)gg;
  94   d->x = gfreduce_exp(&g->r, d->x, x->x, n);
  95 }
  96
  97 static int gread(group *gg, ge_bin *d, const mptext_ops *ops, void *p) {
  98   mp *t; if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1);
  99   mp_drop(d->x); d->x = t; return (0);
 100 }
 101
 102 static int gwrite(group *gg, ge_bin *x, const mptext_ops *ops, void *p) {
 103   int rc = -1;
 104   if (!ops->put("0x", 2, p) && !mp_write(x->x, 16, ops, p)) rc = 0;
 105   return (rc);
 106 }
 107
 108 static mp *gtoint(group *gg, mp *d, ge_bin *x) { return MP_COPY(x->x); }
 109
 110 static int gfromint(group *gg, ge_bin *d, mp *x)
 111   { d->x = MP_COPY(x); return 0; }
 112
 113 static int gtobuf(group *gg, buf *b, ge_bin *x)
 114   { int rc = buf_putmp(b, x->x); return (rc); }
 115
 116 static int gfrombuf(group *gg, buf *b, ge_bin *d) {
 117   gctx_bin *g = (gctx_bin *)gg; mp *x;
 118   if ((x = buf_getmp(b)) == 0) return (-1);
 119   MP_DROP(d->x); d->x = gfreduce_do(&g->r, x, x);
 120   return (0);
 121 }
 122
 123 static int gtoraw(group *gg, buf *b, ge_bin *x) {
 124   gctx_bin *g = (gctx_bin *)gg; octet *q;
 125   if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
 126   mp_storeb(x->x, q, g->g.noctets); return (0);
 127 }
 128
 129 static int gfromraw(group *gg, buf *b, ge_bin *d) {
 130   gctx_bin *g = (gctx_bin *)gg; mp *x; octet *q;
 131   if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
 132   x = mp_loadb(MP_NEW, q, g->g.noctets);
 133   MP_DROP(d->x); d->x = gfreduce_do(&g->r, x, x);
 134   return (0);
 135 }
 136
 137 /* --- @group_binary@ --- *
 138  *
 139  * Arguments:   @const gbin_param *gb@ = group parameters
 140  *
 141  * Returns:     A pointer to the group, or null.
 142  *
 143  * Use:         Constructs an abstract group interface for a subgroup of a
 144  *              prime field.  Group elements are @mp *@ pointers.
 145  */
 146
 147 static const group_ops gops = {
 148   GTY_BINARY, "bin",
 149   gdestroygroup, gcreate, gcopy, gburn, gdestroy,
 150   gsamep, geq, group_stdidentp,
 151   gcheck,
 152   gmul, gsqr, ginv, group_stddiv, gexp, group_stdmexp,
 153   gread, gwrite,
 154   gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf,
 155   gtoraw, gfromraw
 156 };
 157
 158 group *group_binary(const gbin_param *gb)
 159 {
 160   gctx_bin *g;
 161   mp *t;
 162
 163   if (!MP_POSP(gb->p))
 164     return (0);
 165   g = CREATE(gctx_bin);
 166   g->g.ops = &gops;
 167   g->g.nbits = mp_bits(gb->p) - 1;
 168   g->g.noctets = (g->g.nbits + 7) >> 3;
 169   gfreduce_create(&g->r, gb->p);
 170   g->one.x = MP_ONE;
 171   g->g.i = &g->one;
 172   g->gen.x = MP_COPY(gb->g);
 173   g->g.g = &g->gen;
 174   g->g.r = MP_COPY(gb->q);
 175   t = mp_lsl(MP_NEW, MP_ONE, g->g.nbits);
 176   t = mp_sub(t, t, MP_ONE);
 177   g->g.h = MP_NEW; mp_div(&g->g.h, 0, t, gb->q);
 178   MP_DROP(t);
 179   return (&g->g);
 180 }
 181
 182 /*----- That's all, folks -------------------------------------------------*/