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

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Abstraction for prime groups
   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 "mpmont.h"
  35 #include "pgen.h"
  36
  37 #define ge mp *
  38 #include "group.h"
  39 #include "group-guts.h"
  40
  41 /*----- Main code ---------------------------------------------------------*/
  42
  43 /* --- Group operations --- */
  44
  45 static void gdestroygroup(group *gg) {
  46   gctx_bin *g = (gctx_bin *)gg;
  47   mp_drop(g->gen); mp_drop(g->g.r); mp_drop(g->g.h);
  48   gfreduce_destroy(&g->r);
  49   DESTROY(g);
  50 }
  51
  52 static mp **gcreate(group *gg)
  53   { mp **x = CREATE(mp *); *x = MP_COPY(*gg->i); return (x); }
  54
  55 static void gcopy(group *gg, mp **d, mp **x)
  56   { mp *t = MP_COPY(*x); MP_DROP(*d); *d = t; }
  57
  58 static void gburn(group *gg, mp **x) { (*x)->f |= MP_BURN; }
  59
  60 static void gdestroy(group *gg, mp **x) { MP_DROP(*x); DESTROY(x); }
  61
  62 static int gsamep(group *gg, group *hh) {
  63   gctx_bin *g = (gctx_bin *)gg, *h = (gctx_bin *)hh;
  64   return (MP_EQ(g->r.p, h->r.p));
  65 }
  66
  67 static int geq(group *gg, mp **x, mp **y) { return (MP_EQ(*x, *y)); }
  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, mp **d, mp **x, mp **y) {
  80   gctx_bin *g = (gctx_bin *)gg; mp *r = gf_mul(*d, *x, *y);
  81   *d = gfreduce_do(&g->r, r, r);
  82 }
  83
  84 static void gsqr(group *gg, mp **d, mp **x) {
  85   gctx_bin *g = (gctx_bin *)gg; mp *r = gf_sqr(*d, *x);
  86   *d = gfreduce_do(&g->r, r, r);
  87 }
  88
  89 static void ginv(group *gg, mp **d, mp **x)
  90   { gctx_bin *g = (gctx_bin *)gg; *d = gf_modinv(*d, *x, g->r.p); }
  91
  92 static void gexp(group *gg, mp **d, mp **x, mp *n)
  93   { gctx_bin *g = (gctx_bin *)gg; *d = gfreduce_exp(&g->r, *d, *x, n); }
  94
  95 static int gread(group *gg, mp **d, const mptext_ops *ops, void *p) {
  96   mp *t; if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1);
  97   mp_drop(*d); *d = t; return (0);
  98 }
  99
 100 static int gwrite(group *gg, mp **x, const mptext_ops *ops, void *p) {
 101   int rc = -1;
 102   if (!ops->put("0x", 2, p) && !mp_write(*x, 16, ops, p)) rc = 0;
 103   return (rc);
 104 }
 105
 106 static mp *gtoint(group *gg, mp *d, mp **x) { return MP_COPY(*x); }
 107
 108 static int gfromint(group *gg, mp **d, mp *x) { *d = MP_COPY(x); return 0; }
 109
 110 static int gtobuf(group *gg, buf *b, mp **x)
 111   { int rc = buf_putmp(b, *x); return (rc); }
 112
 113 static int gfrombuf(group *gg, buf *b, mp **d) {
 114   gctx_bin *g = (gctx_bin *)gg; mp *x;
 115   if ((x = buf_getmp(b)) == 0) return (-1);
 116   MP_DROP(*d); *d = gfreduce_do(&g->r, x, x);
 117   return (0);
 118 }
 119
 120 static int gtoraw(group *gg, buf *b, mp **x) {
 121   gctx_bin * g = (gctx_bin *)gg; octet *q;
 122   if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
 123   mp_storeb(*x, q, g->g.noctets); return (0);
 124 }
 125
 126 static int gfromraw(group *gg, buf *b, mp **d) {
 127   gctx_bin * g = (gctx_bin *)gg; mp *x; octet *q;
 128   if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
 129   x = mp_loadb(MP_NEW, q, g->g.noctets);
 130   MP_DROP(*d); *d = gfreduce_do(&g->r, x, x);
 131   return (0);
 132 }
 133
 134 /* --- @group_binary@ --- *
 135  *
 136  * Arguments:   @const gbin_param *gb@ = group parameters
 137  *
 138  * Returns:     A pointer to the group, or null.
 139  *
 140  * Use:         Constructs an abstract group interface for a subgroup of a
 141  *              prime field.  Group elements are @mp *@ pointers.
 142  */
 143
 144 static const group_ops gops = {
 145   GTY_BINARY, "bin",
 146   gdestroygroup, gcreate, gcopy, gburn, gdestroy,
 147   gsamep, geq, group_stdidentp,
 148   gcheck,
 149   gmul, gsqr, ginv, group_stddiv, gexp, group_stdmexp,
 150   gread, gwrite,
 151   gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf,
 152   gtoraw, gfromraw
 153 };
 154
 155 group *group_binary(const gbin_param *gb)
 156 {
 157   gctx_bin *g;
 158   mp *t;
 159
 160   if (!MP_POSP(gb->p))
 161     return (0);
 162   g = CREATE(gctx_bin);
 163   g->g.ops = &gops;
 164   g->g.nbits = mp_bits(gb->p) - 1;
 165   g->g.noctets = (g->g.nbits + 7) >> 3;
 166   gfreduce_create(&g->r, gb->p);
 167   g->one = MP_ONE;
 168   g->g.i = &g->one;
 169   g->gen = MP_COPY(gb->g);
 170   g->g.g = &g->gen;
 171   g->g.r = MP_COPY(gb->q);
 172   t = mp_lsl(MP_NEW, MP_ONE, g->g.nbits);
 173   t = mp_sub(t, t, MP_ONE);
 174   g->g.h = MP_NEW; mp_div(&g->g.h, 0, t, gb->q);
 175   MP_DROP(t);
 176   return (&g->g);
 177 }
 178
 179 /*----- That's all, folks -------------------------------------------------*/