git.distorted.org.uk Git - u/mdw/catacomb/blob - g-prime.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_prime *g = (gctx_prime *)gg;
  47   mp_drop(g->gen); mp_drop(g->g.r); mp_drop(g->g.h);
  48   mpmont_destroy(&g->mm);
  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_prime *g = (gctx_prime *)gg, *h = (gctx_prime *)hh;
  64   return (MP_EQ(g->mm.m, h->mm.m));
  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_prime *g = (gctx_prime *)gg; int rc; mp *t;
  71   if (!pgen_primep(g->mm.m, gr)) return ("p is not prime");
  72   t = mp_mul(MP_NEW, g->g.r, g->g.h); t = mp_add(t, t, MP_ONE);
  73   rc = MP_EQ(t, g->mm.m); MP_DROP(t); if (!rc) return ("not a subgroup");
  74   return (group_stdcheck(gg, gr));
  75 }
  76
  77 static void gmul(group *gg, mp **d, mp **x, mp **y)
  78   { gctx_prime *g = (gctx_prime *)gg; *d = mpmont_mul(&g->mm, *d, *x, *y); }
  79
  80 static void gsqr(group *gg, mp **d, mp **x) {
  81   gctx_prime *g = (gctx_prime *)gg; mp *r = mp_sqr(*d, *x);
  82   *d = mpmont_reduce(&g->mm, r, r);
  83 }
  84
  85 static void ginv(group *gg, mp **d, mp **x) {
  86   gctx_prime *g = (gctx_prime *)gg; mp *r = mpmont_reduce(&g->mm, *d, *x);
  87   r = mp_modinv(r, r, g->mm.m); *d = mpmont_mul(&g->mm, r, r, g->mm.r2);
  88 }
  89
  90 static void gexp(group *gg, mp **d, mp **x, mp *n)
  91   { gctx_prime *g = (gctx_prime *)gg; *d = mpmont_expr(&g->mm, *d, *x, n); }
  92
  93 static void gmexp(group *gg, mp **d, const group_expfactor *f, size_t n) {
  94   gctx_prime *g = (gctx_prime *)gg; size_t i;
  95   mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
  96   for (i = 0; i < n; i++) { ff[i].base = *f[i].base; ff[i].exp = f[i].exp; }
  97   *d = mpmont_mexpr(&g->mm, *d, ff, n); xfree(ff);
  98 }
  99
 100 static int gread(group *gg, mp **d, const mptext_ops *ops, void *p) {
 101   gctx_prime *g = (gctx_prime *)gg; mp *t;
 102   if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1);
 103   mp_drop(*d); *d = mpmont_mul(&g->mm, t, t, g->mm.r2); return (0);
 104 }
 105
 106 static int gwrite(group *gg, mp **x, const mptext_ops *ops, void *p) {
 107   gctx_prime *g = (gctx_prime *)gg;
 108   mp *t = mpmont_reduce(&g->mm, MP_NEW, *x);
 109   int rc = mp_write(t, 10, ops, p); MP_DROP(t); return (rc);
 110 }
 111
 112 static mp *gtoint(group *gg, mp *d, mp **x) {
 113   gctx_prime *g = (gctx_prime *)gg;
 114   return (mpmont_reduce(&g->mm, d, *x));
 115 }
 116
 117 static int gfromint(group *gg, mp **d, mp *x) {
 118   gctx_prime *g = (gctx_prime *)gg; mp_div(0, d, x, g->mm.m);
 119   *d = mpmont_mul(&g->mm, *d, *d, g->mm.r2); return (0);
 120 }
 121
 122 static int gtobuf(group *gg, buf *b, mp **x) {
 123   gctx_prime *g = (gctx_prime *)gg;
 124   mp *t = mpmont_reduce(&g->mm, MP_NEW, *x);
 125   int rc = buf_putmp(b, t); MP_DROP(t); return (rc);
 126 }
 127
 128 static int gfrombuf(group *gg, buf *b, mp **d) {
 129   gctx_prime * g = (gctx_prime *)gg; mp *x;
 130   if ((x = buf_getmp(b)) == 0) return (-1);
 131   mp_div(0, &x, x, g->mm.m); mp_drop(*d);
 132   *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0);
 133 }
 134
 135 static int gtoraw(group *gg, buf *b, mp **x) {
 136   gctx_prime *g = (gctx_prime *)gg; octet *q;
 137   mp *t = mpmont_reduce(&g->mm, MP_NEW, *x);
 138   if ((q = buf_get(b, g->g.noctets)) == 0) { MP_DROP(t); return (-1); }
 139   mp_storeb(t, q, g->g.noctets); MP_DROP(t); return (0);
 140 }
 141
 142 static int gfromraw(group *gg, buf *b, mp **d) {
 143   gctx_prime * g = (gctx_prime *)gg; mp *x; octet *q;
 144   if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
 145   x = mp_loadb(MP_NEW, q, g->g.noctets);
 146   mp_div(0, &x, x, g->mm.m); mp_drop(*d);
 147   *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0);
 148 }
 149
 150 /* --- @group_prime@ --- *
 151  *
 152  * Arguments:   @const gprime_param *gp@ = group parameters
 153  *
 154  * Returns:     A pointer to the group, or null.
 155  *
 156  * Use:         Constructs an abstract group interface for a subgroup of a
 157  *              prime field.  Group elements are @mp *@ pointers.
 158  */
 159
 160 static const group_ops gops = {
 161   GTY_PRIME, "prime",
 162   gdestroygroup, gcreate, gcopy, gburn, gdestroy,
 163   gsamep, geq, group_stdidentp,
 164   gcheck,
 165   gmul, gsqr, ginv, group_stddiv, gexp, gmexp,
 166   gread, gwrite,
 167   gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf,
 168   gtoraw, gfromraw
 169 };
 170
 171 group *group_prime(const gprime_param *gp)
 172 {
 173   gctx_prime *g;
 174
 175   if (!MP_POSP(gp->p) || !MP_ODDP(gp->p))
 176     return (0);
 177   g = CREATE(gctx_prime);
 178   g->g.ops = &gops;
 179   g->g.nbits = mp_bits(gp->p);
 180   g->g.noctets = (g->g.nbits + 7) >> 3;
 181   mpmont_create(&g->mm, gp->p);
 182   g->g.i = &g->mm.r;
 183   g->gen = mpmont_mul(&g->mm, MP_NEW, gp->g, g->mm.r2);
 184   g->g.g = &g->gen;
 185   g->g.r = MP_COPY(gp->q);
 186   g->g.h = MP_NEW; mp_div(&g->g.h, 0, gp->p, gp->q);
 187   return (&g->g);
 188 }
 189
 190 /*----- That's all, folks -------------------------------------------------*/