3
* RSA blinding. It is used for timing resistant decryption or signing.
6
/* nettle, low-level cryptographics library
8
* Copyright (C) 2001, 2012 Niels Möller, Nikos Mavrogiannopoulos
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.
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.
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,
34
/* Blinds the c, by computing c *= r^e (mod n), for a random r. Also
35
returns the inverse (ri), for use by rsa_unblind. */
37
_rsa_blind (const struct rsa_public_key *pub,
38
void *random_ctx, nettle_random_func *random,
50
nettle_mpz_random(r, random_ctx, random, pub->n);
53
while (!mpz_invert (ri, r, pub->n));
55
/* c = c*(r^e) mod n */
56
mpz_powm(r, r, pub->e, pub->n);
58
mpz_fdiv_r(c, c, pub->n);
65
_rsa_unblind (const struct rsa_public_key *pub, mpz_t c, const mpz_t ri)
68
mpz_fdiv_r(c, c, pub->n);