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