--- /dev/null
+/* -*-c-*-
+ *
+ * $Id: group-stdops.c,v 1.1 2004/04/01 12:50:09 mdw Exp $
+ *
+ * Standard group operations
+ *
+ * (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.
+ */
+
+/*----- Revision history --------------------------------------------------*
+ *
+ * $Log: group-stdops.c,v $
+ * Revision 1.1 2004/04/01 12:50:09 mdw
+ * Add cyclic group abstraction, with test code. Separate off exponentation
+ * functions for better static linking. Fix a buttload of bugs on the way.
+ * Generally ensure that negative exponents do inversion correctly. Add
+ * table of standard prime-field subgroups. (Binary field subgroups are
+ * currently unimplemented but easy to add if anyone ever finds a good one.)
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "group.h"
+#include "pgen.h"
+
+/*----- Handy functions ---------------------------------------------------*/
+
+/* --- @group_check@ --- *
+ *
+ * Arguments: @group *g@ = an abstract group
+ * @ge *x@ = a group element
+ *
+ * Returns: Zero on success, nonzero for failure.
+ *
+ * Use: Checks that @x@ is a valid group element. This may take a
+ * while, since it checks that %$x^h \ne 1$% and %$x^r = 1$%.
+ */
+
+int group_check(group *g, ge *x)
+{
+ ge *d = G_CREATE(g);
+ int rc;
+
+ G_EXP(g, d, x, g->h); rc = !G_IDENTP(g, d);
+ if (rc) { G_EXP(g, d, x, g->r); rc = G_IDENTP(g, d); }
+ G_DESTROY(g, d);
+ if (!rc) return (-1);
+ return (0);
+}
+
+/* --- @group_samep@ --- *
+ *
+ * Arguments: @group *g, *h@ = two abstract groups
+ *
+ * Returns: Nonzero if the groups are in fact identical (not just
+ * isomorphic).
+ *
+ * Use: Checks to see whether two groups are actually the same. This
+ * function does the full check: the group operatrion @samep@
+ * just does the group-specific details.
+ */
+
+int group_samep(group *g, group *h)
+{
+ return (g->ops == h->ops &&
+ MP_EQ(g->r, h->r) && MP_EQ(g->h, h->h) &&
+ G_EQ(g, g->i, h->i) && G_EQ(g, g->g, h->g) &&
+ G_SAMEP(g, h));
+}
+
+/*----- Standard implementations ------------------------------------------*/
+
+/* --- @group_stdidentp@ --- *
+ *
+ * Arguments: @group *g@ = abstract group
+ * @ge *x@ = group element
+ *
+ * Returns: Nonzero if %$x$% is the group identity.
+ */
+
+int group_stdidentp(group *g, ge *x) { return (G_EQ(g, x, g->i)); }
+
+/* --- @group_stdsqr@ --- *
+ *
+ * Arguments: @group *g@ = abstract group
+ * @ge *d@ = destination pointer
+ * @ge *x@ = group element
+ *
+ * Returns: ---
+ *
+ * Use: Computes %$d = x^2$% as %$d = x x$%.
+ */
+
+void group_stdsqr(group *g, ge *d, ge *x) { G_MUL(g, d, x, x); }
+
+/* --- @group_stddiv@ --- *
+ *
+ * Arguments: @group *g@ = abstract group
+ * @ge *d@ = destination pointer
+ * @ge *x@ = dividend
+ * @ge *y@ = divisor
+ *
+ * Returns: ---
+ *
+ * Use: Computes %$d = x/y$% as %$d = x y^{-1}$%.
+ */
+
+void group_stddiv(group *g, ge *d, ge *x, ge *y)
+{
+ G_INV(g, d, y);
+ G_MUL(g, d, x, d);
+}
+
+/* --- @group_stdtoec@ --- *
+ *
+ * Arguments: @group *g@ = abstract group
+ * @ec *d@ = destination point
+ * @ge *x@ = group element
+ *
+ * Returns: @-1@, indicating failure.
+ *
+ * Use: Fails to convert a group element to an elliptic curve point.
+ */
+
+int group_stdtoec(group *g, ec *d, ge *x) { return (-1); }
+
+/* --- @group_stdfromec@ --- *
+ *
+ * Arguments: @group *g@ = abstract group
+ * @ge *d@ = destination pointer
+ * @ec *p@ = elliptic curve point
+ *
+ * Returns: Zero for success, @-1@ on failure.
+ *
+ * Use: Converts %$p$% to a group element by converting its %$x$%-
+ * coordinate.
+ */
+
+int group_stdfromec(group *g, ge *d, ec *p)
+ { if (EC_ATINF(p)) return (-1); return (G_FROMINT(g, d, p->x)); }
+
+/* --- @group_stdcheck@ --- *
+ *
+ * Arguments: @group *g@ = abstract group
+ * @grand *gr@ = random number source.
+ *
+ * Returns: Null on success, or a pointer to an error message.
+ */
+
+const char *group_stdcheck(group *g, grand *gr)
+{
+ ge *t;
+ int rc;
+
+ if (!pgen_primep(g->r, gr)) return ("group order not prime");
+ t = G_CREATE(g); G_EXP(g, t, g->g, g->r);
+ rc = G_IDENTP(g, t); G_DESTROY(g, t);
+ if (!rc) return ("generator not in the group");
+ return (0);
+}
+
+/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff