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/*
 * Copyright (c) 2000, 2001, 2002 Virtual Unlimited B.V.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

/*!\file elgamal.h
 * \brief ElGamal algorithm, headers.
 * \author Bob Deblier <bob.deblier@pandora.be>
 * \ingroup DL_m DL_elgamal_m
 */

#ifndef _ELGAMAL_H
#define _ELGAMAL_H

#include "mpbarrett.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * The raw ElGamal signing funcion, variant 1.
 *
 * Signing equations:
 *
 * \li \f$r=g^{k}\ \textrm{mod}\ p\f$
 * \li \f$s=k^{-1}(h(m)-xr)\ \textrm{mod}\ (p-1)\f$
 *
 * @param p		The prime.
 * @param n		The reducer mod (p-1).
 * @param g		The generator.
 * @param rgc		The pseudo-random generator.
 * @param hm		The hash to be signed.
 * @param x		The private key value.
 * @param r		The signature's \e r value.
 * @param s		The signature's \e r value.
 * @retval		0 on success, -1 on failure.
 */
BEECRYPTAPI /*@unused@*/
int elgv1sign(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, randomGeneratorContext* rgc, const mpnumber* hm, const mpnumber* x, mpnumber* r, mpnumber* s)
	/*@modifies r, s */;

/**
 * The raw ElGamal signing funcion, variant 3.
 *
 * Signing equations:
 *
 * \li \f$r=g^{k}\ \textrm{mod}\ p\f$
 * \li \f$s=xr+kh(m)\ \textrm{mod}\ (p-1)\f$
 *
 * @param p		The prime.
 * @param n		The reducer mod (p-1).
 * @param g		The generator.
 * @param rgc		The pseudo-random generator.
 * @param hm		The hash to be signed.
 * @param x		The private key value.
 * @param r		The signature's \e r value.
 * @param s		The signature's \e r value.
 * @retval		0 on success, -1 on failure.
 */
BEECRYPTAPI /*@unused@*/
int elgv3sign(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, randomGeneratorContext* rgc, const mpnumber* hm, const mpnumber* x, mpnumber* r, mpnumber* s)
	/*@modifies r, s */;

/**
 * The raw ElGamal verification funcion, variant 1.
 *
 * Verifying equations:
 *
 * \li Check \f$0<r<p\f$ and \f$0<s<(p-1)\f$
 * \li \f$v_1=y^{r}r^{s}\ \textrm{mod}\ p\f$
 * \li \f$v_2=g^{h(m)}\ \textrm{mod}\ p\f$
 * \li Check \f$v_1=v_2\f$
 *
 * @warning The return type of this function should be a boolean, but since
 *          that type isn't as portable, an int is used.
 *
 * @param p		The prime.
 * @param n		The reducer mod (p-1).
 * @param g		The generator.
 * @param hm		The hash to be signed.
 * @param y		The public key value.
 * @param r		The signature's \e r value.
 * @param s		The signature's \e r value.
 * @retval		1 on success, 0 on failure.
 */
BEECRYPTAPI /*@unused@*/
int elgv1vrfy(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, const mpnumber* hm, const mpnumber* y, const mpnumber* r, const mpnumber* s)
	/*@*/;

/**
 * The raw ElGamal verification funcion, variant 3.
 *
 * Verifying equations:
 *
 * \li Check \f$0<r<p\f$ and \f$0<s<(p-1)\f$
 * \li \f$v_1=g^{s}\ \textrm{mod}\ p\f$
 * \li \f$v_2=y^{r}r^{h(m)}\ \textrm{mod}\ p\f$
 * \li Check \f$v_1=v_2\f$
 *
 * @warning The return type of this function should be a boolean, but since
 *          that type isn't as portable, an int is used.
 *
 * @param p		The prime.
 * @param n		The reducer mod (p-1).
 * @param g		The generator.
 * @param hm		The hash to be signed.
 * @param y		The public key value.
 * @param r		The signature's \e r value.
 * @param s		The signature's \e r value.
 * @retval		1 on success, 0 on failure.
 */
BEECRYPTAPI /*@unused@*/
int elgv3vrfy(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, const mpnumber* hm, const mpnumber* y, const mpnumber* r, const mpnumber* s)
	/*@*/;

#ifdef __cplusplus
}
#endif

#endif