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/* xtea.c
* Implementation of XTEA cipher
* By Ahmad Fatoum <ahmad[AT]a3f.at>
* Copyright 2017 Ahmad Fatoum
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*/
#include <glib.h>
#include <string.h>
#include "pint.h"
#include "xtea.h"
void decrypt_xtea_ecb(guint8 output[8], const guint8 v_in[8], const guint32 key[4], guint num_rounds)
{
guint i;
guint32 v[2], delta = 0x9E3779B9, sum = delta * num_rounds;
v[0] = pntoh32(&v_in[0]);
v[1] = pntoh32(&v_in[4]);
for (i = 0; i < num_rounds; i++) {
v[1] -= (((v[0] << 4) ^ (v[0] >> 5)) + v[0]) ^ (sum + key[(sum >> 11) & 3]);
sum -= delta;
v[0] -= (((v[1] << 4) ^ (v[1] >> 5)) + v[1]) ^ (sum + key[sum & 3]);
}
v[0] = GUINT32_TO_BE(v[0]);
v[1] = GUINT32_TO_BE(v[1]);
memcpy(output, v, sizeof v);
}
void decrypt_xtea_le_ecb(guint8 output[8], const guint8 v_in[8], const guint32 key[4], guint num_rounds)
{
guint i;
guint32 v[2], delta = 0x9E3779B9, sum = delta * num_rounds;
v[0] = pletoh32(&v_in[0]);
v[1] = pletoh32(&v_in[4]);
for (i = 0; i < num_rounds; i++) {
v[1] -= (((v[0] << 4) ^ (v[0] >> 5)) + v[0]) ^ (sum + key[(sum >> 11) & 3]);
sum -= delta;
v[0] -= (((v[1] << 4) ^ (v[1] >> 5)) + v[1]) ^ (sum + key[sum & 3]);
}
v[0] = GUINT32_TO_LE(v[0]);
v[1] = GUINT32_TO_LE(v[1]);
memcpy(output, v, sizeof v);
}
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