release/src/router/nettle/rsa-verify.c

   1 /* rsa-verify.c
   2  *
   3  * Verifying RSA signatures.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2001, 2003 Niels Möller
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 #if HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include "rsa.h"
  31
  32 #include "bignum.h"
  33
  34 int
  35 _rsa_verify(const struct rsa_public_key *key,
  36             const mpz_t m,
  37             const mpz_t s)
  38 {
  39   int res;
  40
  41   mpz_t m1;
  42
  43   if ( (mpz_sgn(s) <= 0)
  44        || (mpz_cmp(s, key->n) >= 0) )
  45     return 0;
  46
  47   mpz_init(m1);
  48
  49   mpz_powm(m1, s, key->e, key->n);
  50
  51   res = !mpz_cmp(m, m1);
  52
  53   mpz_clear(m1);
  54
  55   return res;
  56 }