3 * The RSA publickey algorithm. PKCS#1 encryption.
6 /* nettle, low-level cryptographics library
8 * Copyright (C) 2001 Niels Möller
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., 59 Temple Place - Suite 330, Boston,
37 #include "nettle-internal.h"
40 rsa_decrypt(const struct rsa_private_key *key,
41 unsigned *length, uint8_t *message,
42 const mpz_t gibberish)
44 TMP_DECL(em, uint8_t, NETTLE_MAX_BIGNUM_BITS / 8);
47 unsigned message_length;
52 rsa_compute_root(key, m, gibberish);
54 TMP_ALLOC(em, key->size);
55 nettle_mpz_get_str_256(key->size, em, m);
59 if (em[0] || em[1] != 2)
62 terminator = memchr(em + 2, 0, key->size - 2);
67 padding = terminator - (em + 2);
71 message_length = key->size - 3 - padding;
73 if (*length < message_length)
76 memcpy(message, terminator + 1, message_length);
77 *length = message_length;