release/src/router/nettle/rsa.c

   1 /* rsa.c
   2  *
   3  * The RSA publickey algorithm.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2001 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 void
  35 rsa_public_key_init(struct rsa_public_key *key)
  36 {
  37   mpz_init(key->n);
  38   mpz_init(key->e);
  39
  40   /* Not really necessary, but it seems cleaner to initialize all the
  41    * storage. */
  42   key->size = 0;
  43 }
  44
  45 void
  46 rsa_public_key_clear(struct rsa_public_key *key)
  47 {
  48   mpz_clear(key->n);
  49   mpz_clear(key->e);
  50 }
  51
  52 /* Computes the size, in octets, of a the modulo. Returns 0 if the
  53  * modulo is too small to be useful. */
  54
  55 unsigned
  56 _rsa_check_size(mpz_t n)
  57 {
  58   /* Round upwards */
  59   unsigned size = (mpz_sizeinbase(n, 2) + 7) / 8;
  60
  61   if (size < RSA_MINIMUM_N_OCTETS)
  62     return 0;
  63
  64   return size;
  65 }
  66
  67 int
  68 rsa_public_key_prepare(struct rsa_public_key *key)
  69 {
  70   key->size = _rsa_check_size(key->n);
  71
  72   return (key->size > 0);
  73 }