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/* rsa-verify.c
*
* Verifying RSA signatures.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2001, 2003 Niels Möller
*
* The nettle 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.
*
* The nettle 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 the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#if WITH_PUBLIC_KEY
#include "rsa.h"
#include "bignum.h"
int
_rsa_verify(const struct rsa_public_key *key,
const mpz_t m,
const mpz_t s)
{
int res;
mpz_t m1;
if ( (mpz_sgn(s) <= 0)
|| (mpz_cmp(s, key->n) >= 0) )
return 0;
mpz_init(m1);
mpz_powm(m1, s, key->e, key->n);
/* FIXME: Is it cheaper to convert m1 to a string and check that? */
res = !mpz_cmp(m, m1);
mpz_clear(m1);
return res;
}
#endif /* WITH_PUBLIC_KEY */
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