/*
 * 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 rsa.c
 * \brief RSA algorithm.
 * \author Bob Deblier <bob.deblier@pandora.be>
 * \ingroup IF_m IF_rsa_m
 */

#include "system.h"
#include "rsa.h"
#include "mp.h"
#include "debug.h"

int rsapub(const rsapk* pk, const mpnumber* m, mpnumber* c)
{
	register size_t size = pk->n.size;
	register mpw* temp;

	if (mpgex(m->size, m->data, pk->n.size, pk->n.modl))
		return -1;

	temp = (mpw*) malloc((4*size+2)*sizeof(*temp));

	if (temp)
	{
		mpnsize(c, size);

		mpbpowmod_w(&pk->n, m->size, m->data, pk->e.size, pk->e.data, c->data, temp);
		free(temp);

		return 0;
	}
	return -1;
}

int rsapri(const rsakp* kp, const mpnumber* c, mpnumber* m)
{
	register size_t size = kp->n.size;
	register mpw* temp;

	if (mpgex(c->size, c->data, kp->n.size, kp->n.modl))
		return -1;

	temp = (mpw*) malloc((4*size+2) * sizeof(*temp));

	if (temp)
	{
		mpnsize(m, size);
		mpbpowmod_w(&kp->n, c->size, c->data, kp->d.size, kp->d.data, m->data, temp);

		free(temp);

		return 0;
	}
	return -1;
}

int rsapricrt(const rsakp* kp, const mpnumber* c, mpnumber* m)
{
	register size_t nsize = kp->n.size;
	register size_t psize = kp->p.size;
	register size_t qsize = kp->q.size;

	register mpw* ptemp;
	register mpw* qtemp;

	if (mpgex(c->size, c->data, kp->n.size, kp->n.modl))
		return -1;

	ptemp = (mpw*) malloc((6*psize+2)*sizeof(*ptemp));
	if (ptemp == (mpw*) 0)
		return -1;

	qtemp = (mpw*) malloc((6*qsize+2)*sizeof(*qtemp));
	if (qtemp == (mpw*) 0)
	{
		free(ptemp);
		return -1;
	}

	/* resize c for powmod p */
	mpsetx(psize*2, ptemp, c->size, c->data);

	/* reduce modulo p before we powmod */
	mpbmod_w(&kp->p, ptemp, ptemp+psize, ptemp+2*psize);

	/* compute j1 = c^d1 mod p, store @ ptemp */
	mpbpowmod_w(&kp->p, psize, ptemp+psize, kp->d1.size, kp->d1.data, ptemp, ptemp+2*psize);

	/* resize c for powmod q */
	mpsetx(qsize*2, qtemp, c->size, c->data);

	/* reduce modulo q before we powmod */
	mpbmod_w(&kp->q, qtemp, qtemp+qsize, qtemp+2*qsize);

	/* compute j2 = c^d2 mod q, store @ qtemp */
	mpbpowmod_w(&kp->q, qsize, qtemp+qsize, kp->d2.size, kp->d2.data, qtemp, qtemp+2*qsize);

	/* compute j1-j2 mod p, store @ ptemp */
	mpbsubmod_w(&kp->p, psize, ptemp, qsize, qtemp, ptemp, ptemp+2*psize);

	/* compute h = c*(j1-j2) mod p, store @ ptemp */
	mpbmulmod_w(&kp->p, psize, ptemp, psize, kp->c.data, ptemp, ptemp+2*psize);

	/* make sure the message gets the proper size */
	mpnsize(m, nsize);

	/* compute m = h*q + j2 */
	mpmul(m->data, psize, ptemp, qsize, kp->q.modl);
	(void) mpaddx(nsize, m->data, qsize, qtemp);

	free(ptemp);
	free(qtemp);

	return 0;
}

int rsavrfy(const rsapk* pk, const mpnumber* m, const mpnumber* c)
{
	int rc;
	register size_t size = pk->n.size;
	register mpw* temp;

	if (mpgex(m->size, m->data, pk->n.size, pk->n.modl))
		return -1;

	if (mpgex(c->size, c->data, pk->n.size, pk->n.modl))
		return 0;

	temp = (mpw*) malloc((5*size+2) * sizeof(*temp));

	if (temp)
	{
		mpbpowmod_w(&pk->n, c->size, c->data, pk->e.size, pk->e.data, temp, temp+size);

		rc = mpeqx(size, temp, m->size, m->data);

		free(temp);

		return rc;
	}
	return 0;
}