X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/986527ae4af14be68551d0b49a1145bb3e89f259..3688eb757240b2332f67ec827be8caf6f6abe924:/g-bin.c

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+/* -*-c-*-
+ *
+ * $Id$
+ *
+ * Abstraction for prime groups
+ *
+ * (c) 2004 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <mLib/sub.h>
+
+#include "mpmont.h"
+#include "pgen.h"
+
+#define ge mp *
+#include "group.h"
+#include "group-guts.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- Group operations --- */
+
+static void gdestroygroup(group *gg) {
+  gctx_bin *g = (gctx_bin *)gg;
+  mp_drop(g->gen); mp_drop(g->g.r); mp_drop(g->g.h);
+  gfreduce_destroy(&g->r);
+  DESTROY(g);
+}
+
+static mp **gcreate(group *gg)
+  { mp **x = CREATE(mp *); *x = MP_COPY(*gg->i); return (x); }
+
+static void gcopy(group *gg, mp **d, mp **x)
+  { mp *t = MP_COPY(*x); MP_DROP(*d); *d = t; }
+
+static void gburn(group *gg, mp **x) { (*x)->f |= MP_BURN; }
+
+static void gdestroy(group *gg, mp **x) { MP_DROP(*x); DESTROY(x); }
+
+static int gsamep(group *gg, group *hh) {
+  gctx_bin *g = (gctx_bin *)gg, *h = (gctx_bin *)hh;
+  return (MP_EQ(g->r.p, h->r.p));
+}
+
+static int geq(group *gg, mp **x, mp **y) { return (MP_EQ(*x, *y)); }
+
+static const char *gcheck(group *gg, grand *gr) {
+  gctx_bin *g = (gctx_bin *)gg; int rc; mp *t, *tt;
+  if (!gf_irreduciblep(g->r.p)) return ("p is not irreducible");
+  t = mp_mul(MP_NEW, g->g.r, g->g.h); t = mp_add(t, t, MP_ONE);
+  tt = mp_lsl(MP_NEW, MP_ONE, g->g.nbits);
+  rc = MP_EQ(t, tt); MP_DROP(t); MP_DROP(tt);
+  if (!rc) return ("not a subgroup");
+  return (group_stdcheck(gg, gr));
+}
+
+static void gmul(group *gg, mp **d, mp **x, mp **y) {
+  gctx_bin *g = (gctx_bin *)gg; mp *r = gf_mul(*d, *x, *y);
+  *d = gfreduce_do(&g->r, r, r);
+}
+
+static void gsqr(group *gg, mp **d, mp **x) {
+  gctx_bin *g = (gctx_bin *)gg; mp *r = gf_sqr(*d, *x);
+  *d = gfreduce_do(&g->r, r, r);
+}
+
+static void ginv(group *gg, mp **d, mp **x)
+  { gctx_bin *g = (gctx_bin *)gg; *d = gf_modinv(*d, *x, g->r.p); }
+
+static void gexp(group *gg, mp **d, mp **x, mp *n)
+  { gctx_bin *g = (gctx_bin *)gg; *d = gfreduce_exp(&g->r, *d, *x, n); }
+
+static int gread(group *gg, mp **d, const mptext_ops *ops, void *p) {
+  mp *t; if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1);
+  mp_drop(*d); *d = t; return (0);
+}
+
+static int gwrite(group *gg, mp **x, const mptext_ops *ops, void *p) {
+  int rc = -1;
+  if (!ops->put("0x", 2, p) && !mp_write(*x, 16, ops, p)) rc = 0;
+  return (rc);
+}
+
+static mp *gtoint(group *gg, mp *d, mp **x) { return MP_COPY(*x); }
+
+static int gfromint(group *gg, mp **d, mp *x) { *d = MP_COPY(x); return 0; }
+
+static int gtobuf(group *gg, buf *b, mp **x)
+  { int rc = buf_putmp(b, *x); return (rc); }
+
+static int gfrombuf(group *gg, buf *b, mp **d) {
+  gctx_bin *g = (gctx_bin *)gg; mp *x;
+  if ((x = buf_getmp(b)) == 0) return (-1);
+  MP_DROP(*d); *d = gfreduce_do(&g->r, x, x);
+  return (0);
+}
+
+static int gtoraw(group *gg, buf *b, mp **x) {
+  gctx_bin * g = (gctx_bin *)gg; octet *q;
+  if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
+  mp_storeb(*x, q, g->g.noctets); return (0);
+}
+
+static int gfromraw(group *gg, buf *b, mp **d) {
+  gctx_bin * g = (gctx_bin *)gg; mp *x; octet *q;
+  if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
+  x = mp_loadb(MP_NEW, q, g->g.noctets);
+  MP_DROP(*d); *d = gfreduce_do(&g->r, x, x);
+  return (0);
+}
+
+/* --- @group_binary@ --- *
+ *
+ * Arguments:	@const gbin_param *gb@ = group parameters
+ *
+ * Returns:	A pointer to the group, or null.
+ *
+ * Use:		Constructs an abstract group interface for a subgroup of a
+ *		prime field.  Group elements are @mp *@ pointers.
+ */
+
+static const group_ops gops = {
+  GTY_BINARY, "bin",
+  gdestroygroup, gcreate, gcopy, gburn, gdestroy,
+  gsamep, geq, group_stdidentp,
+  gcheck,
+  gmul, gsqr, ginv, group_stddiv, gexp, group_stdmexp,
+  gread, gwrite,
+  gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf,
+  gtoraw, gfromraw
+};
+
+group *group_binary(const gbin_param *gb)
+{
+  gctx_bin *g;
+  mp *t;
+
+  if (!MP_POSP(gb->p))
+    return (0);
+  g = CREATE(gctx_bin);
+  g->g.ops = &gops;
+  g->g.nbits = mp_bits(gb->p) - 1;
+  g->g.noctets = (g->g.nbits + 7) >> 3;
+  gfreduce_create(&g->r, gb->p);
+  g->one = MP_ONE;
+  g->g.i = &g->one;
+  g->gen = MP_COPY(gb->g);
+  g->g.g = &g->gen;
+  g->g.r = MP_COPY(gb->q);
+  t = mp_lsl(MP_NEW, MP_ONE, g->g.nbits);
+  t = mp_sub(t, t, MP_ONE);
+  g->g.h = MP_NEW; mp_div(&g->g.h, 0, t, gb->q);
+  MP_DROP(t);
+  return (&g->g);
+}
+
+/*----- That's all, folks -------------------------------------------------*/