2 * Implementation of XTEA cipher
3 * By Ahmad Fatoum <ahmad[AT]a3f.at>
4 * Copyright 2017 Ahmad Fatoum
6 * Wireshark - Network traffic analyzer
7 * By Gerald Combs <gerald@wireshark.org>
8 * Copyright 1998 Gerald Combs
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version 2
13 * of the License, or (at your option) any later version.
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
32 void decrypt_xtea_ecb(guint8 output[8], const guint8 v_in[8], const guint32 key[4], guint num_rounds)
35 guint32 v[2], delta = 0x9E3779B9, sum = delta * num_rounds;
37 v[0] = pntoh32(&v_in[0]);
38 v[1] = pntoh32(&v_in[4]);
40 for (i = 0; i < num_rounds; i++) {
41 v[1] -= (((v[0] << 4) ^ (v[0] >> 5)) + v[0]) ^ (sum + key[(sum >> 11) & 3]);
43 v[0] -= (((v[1] << 4) ^ (v[1] >> 5)) + v[1]) ^ (sum + key[sum & 3]);
46 v[0] = GUINT32_TO_BE(v[0]);
47 v[1] = GUINT32_TO_BE(v[1]);
49 memcpy(output, v, sizeof v);
52 void decrypt_xtea_le_ecb(guint8 output[8], const guint8 v_in[8], const guint32 key[4], guint num_rounds)
55 guint32 v[2], delta = 0x9E3779B9, sum = delta * num_rounds;
57 v[0] = pletoh32(&v_in[0]);
58 v[1] = pletoh32(&v_in[4]);
60 for (i = 0; i < num_rounds; i++) {
61 v[1] -= (((v[0] << 4) ^ (v[0] >> 5)) + v[0]) ^ (sum + key[(sum >> 11) & 3]);
63 v[0] -= (((v[1] << 4) ^ (v[1] >> 5)) + v[1]) ^ (sum + key[sum & 3]);
66 v[0] = GUINT32_TO_LE(v[0]);
67 v[1] = GUINT32_TO_LE(v[1]);
69 memcpy(output, v, sizeof v);