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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
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "xtea.h"
#include <string.h>
#include "pint.h"
void decrypt_xtea_ecb(uint8_t plaintext[8], const uint8_t ciphertext[8], const uint32_t key[4], unsigned num_rounds)
{
unsigned i;
uint32_t v[2], delta = 0x9E3779B9, sum = delta * num_rounds;
v[0] = pntoh32(&ciphertext[0]);
v[1] = pntoh32(&ciphertext[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(plaintext, v, sizeof v);
}
void decrypt_xtea_le_ecb(uint8_t plaintext[8], const uint8_t ciphertext[8], const uint32_t key[4], unsigned num_rounds)
{
unsigned i;
uint32_t v[2], delta = 0x9E3779B9, sum = delta * num_rounds;
v[0] = pletoh32(&ciphertext[0]);
v[1] = pletoh32(&ciphertext[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(plaintext, v, sizeof v);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 4
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=4 tabstop=8 expandtab:
* :indentSize=4:tabSize=8:noTabs=true:
*/
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