[u/mdw/catacomb] / group-stdops.c

/* -*-c-*-
 *
 * $Id: group-stdops.c,v 1.3 2004/04/17 09:58:37 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.
 */

/*----- 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 %$x \ne 1$% and %$x^r = 1$%.
 */

int group_check(group *g, ge *x)
{
  ge *d = G_CREATE(g);
  int rc;

  G_EXP(g, d, x, g->r);
  rc = (G_IDENTP(g, d) && !G_IDENTP(g, x));
  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
 *		@const 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, const 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 -------------------------------------------------*/
Commit	Line	Data
34e4f738	1	/* --c--
34e4f738	2	*
5c3f75ec	3	* $Id: group-stdops.c,v 1.3 2004/04/17 09:58:37 mdw Exp $
34e4f738	4	*
	5	* Standard group operations
	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
34e4f738	30	/----- Header files ------------------------------------------------------/
	31
	32	#include "group.h"
	33	#include "pgen.h"
	34
	35	/----- Handy functions ---------------------------------------------------/
	36
	37	/* --- @group_check@ --- *
	38	*
	39	* Arguments: @group *g@ = an abstract group
	40	* @ge *x@ = a group element
	41	*
	42	* Returns: Zero on success, nonzero for failure.
	43	*
	44	* Use: Checks that @x@ is a valid group element. This may take a
5c3f75ec	45	* while, since it checks that %$x \ne 1$% and %$x^r = 1$%.
34e4f738	46	*/
	47
	48	int group_check(group g, ge x)
	49	{
	50	ge *d = G_CREATE(g);
	51	int rc;
	52
5c3f75ec	53	G_EXP(g, d, x, g->r);
5c3f75ec	54	rc = (G_IDENTP(g, d) && !G_IDENTP(g, x));
34e4f738	55	G_DESTROY(g, d);
	56	if (!rc) return (-1);
	57	return (0);
	58	}
	59
	60	/* --- @group_samep@ --- *
	61	*
	62	* Arguments: @group g, h@ = two abstract groups
	63	*
	64	* Returns: Nonzero if the groups are in fact identical (not just
	65	* isomorphic).
	66	*
	67	* Use: Checks to see whether two groups are actually the same. This
	68	* function does the full check: the group operatrion @samep@
	69	* just does the group-specific details.
	70	*/
	71
	72	int group_samep(group g, group h)
	73	{
	74	return (g->ops == h->ops &&
	75	MP_EQ(g->r, h->r) && MP_EQ(g->h, h->h) &&
	76	G_EQ(g, g->i, h->i) && G_EQ(g, g->g, h->g) &&
	77	G_SAMEP(g, h));
	78	}
	79
	80	/----- Standard implementations ------------------------------------------/
	81
	82	/* --- @group_stdidentp@ --- *
	83	*
	84	* Arguments: @group *g@ = abstract group
	85	* @ge *x@ = group element
	86	*
	87	* Returns: Nonzero if %$x$% is the group identity.
	88	*/
	89
	90	int group_stdidentp(group g, ge x) { return (G_EQ(g, x, g->i)); }
	91
	92	/* --- @group_stdsqr@ --- *
	93	*
	94	* Arguments: @group *g@ = abstract group
	95	* @ge *d@ = destination pointer
	96	* @ge *x@ = group element
	97	*
	98	* Returns: ---
	99	*
	100	* Use: Computes %$d = x^2$% as %$d = x x$%.
	101	*/
	102
	103	void group_stdsqr(group g, ge d, ge *x) { G_MUL(g, d, x, x); }
	104
	105	/* --- @group_stddiv@ --- *
	106	*
	107	* Arguments: @group *g@ = abstract group
	108	* @ge *d@ = destination pointer
	109	* @ge *x@ = dividend
	110	* @ge *y@ = divisor
	111	*
	112	* Returns: ---
	113	*
	114	* Use: Computes %$d = x/y$% as %$d = x y^{-1}$%.
	115	*/
	116
	117	void group_stddiv(group g, ge d, ge x, ge y)
	118	{
119	G_INV(g, d, y);
120	G_MUL(g, d, x, d);
121	}
122
123	/* --- @group_stdtoec@ --- *
124	*
125	* Arguments: @group *g@ = abstract group
126	* @ec *d@ = destination point
127	* @ge *x@ = group element
128	*
129	* Returns: @-1@, indicating failure.
130	*
131	* Use: Fails to convert a group element to an elliptic curve point.
132	*/
133
134	int group_stdtoec(group g, ec d, ge *x) { return (-1); }
135
136	/* --- @group_stdfromec@ --- *
137	*
138	* Arguments: @group *g@ = abstract group
139	* @ge *d@ = destination pointer
5c3f75ec	140	* @const ec *p@ = elliptic curve point
34e4f738	141	*
	142	* Returns: Zero for success, @-1@ on failure.
	143	*
	144	* Use: Converts %$p$% to a group element by converting its %$x$%-
	145	* coordinate.
	146	*/
	147
5c3f75ec	148	int group_stdfromec(group g, ge d, const ec *p)
34e4f738	149	{ if (EC_ATINF(p)) return (-1); return (G_FROMINT(g, d, p->x)); }
	150
	151	/* --- @group_stdcheck@ --- *
	152	*
	153	* Arguments: @group *g@ = abstract group
	154	* @grand *gr@ = random number source.
	155	*
	156	* Returns: Null on success, or a pointer to an error message.
	157	*/
	158
	159	const char group_stdcheck(group g, grand *gr)
	160	{
	161	ge *t;
	162	int rc;
	163
	164	if (!pgen_primep(g->r, gr)) return ("group order not prime");
	165	t = G_CREATE(g); G_EXP(g, t, g->g, g->r);
	166	rc = G_IDENTP(g, t); G_DESTROY(g, t);
	167	if (!rc) return ("generator not in the group");
	168	return (0);
	169	}
	170
	171	/----- That's all, folks -------------------------------------------------/