I am trying to decrypt a code encrypted with XTEA. I have been using a script found here, http://goo.gl/xCpgs and it works within its own encrypt/decrypt example. The problem is that it will not decrypt a code given to me by my client. In the code examples description it says the "key" is 16 characters, but the key I have from my client is 32 characters so I think this may be part of the problem, but I cannot find out in the code how to make it work with a 32 char key (if that is even the issue).
Below is the class from the link above and below that are sample encrypt and decrypt strings. If anyone can provide help or a better solution, it is greatly appreciated. My guess is that it is only allowing 16 of my 32 char key. I tried to use a 32 char key, but the code still seemed to only want 16. Help!
I also read something about XTEA only working within the same code language each side of the crypt was made. Can anyone validate this?
Below is the class from the link above and below that are sample encrypt and decrypt strings. If anyone can provide help or a better solution, it is greatly appreciated. My guess is that it is only allowing 16 of my 32 char key. I tried to use a 32 char key, but the code still seemed to only want 16. Help!
I also read something about XTEA only working within the same code language each side of the crypt was made. Can anyone validate this?
Code:
<?php
/* PHP Implementation of XTEA (www.php-einfach.de)
*
* XTEA was designed in 1997 by David Wheeler and Roger Needham
* of the Cambridge Computer Laboratory.
* It is not subject to any patents.
*
* It is a 64-bit Feistel cipher, consisting of 64 rounds.
* XTA has a key length of 128 bits.
*
*
* ***********************
* Diese Implementierung darf frei verwendet werden, der Autor uebernimmt keine
* Haftung fuer die Richtigkeit, Fehlerfreiheit oder die Funktionsfaehigkeit dieses Scripts.
* Benutzung auf eigene Gefahr.
*
* Ueber einen Link auf www.php-einfach.de wuerden wir uns freuen.
*
* ************************
* Usage:
*
* include("xtea.class.php");
*
* $xtea = new XTEA("secret Key");
* $cipher = $xtea->Encrypt("Hello World"); //Encrypts 'Hello World'
* $plain = $xtea->Decrypt($cipher); //Decrypts the cipher text
*
* echo $plain;
*
*/
class XTEA {
//Private
var $key;
// CBC or ECB Mode
// normaly, CBC Mode would be the right choice
var $cbc = 1;
function XTEA($key) {
$this->key_setup($key);
}
//encrypt
function encrypt($text) {
$n = strlen($text);
if($n%8 != 0) $lng = ($n+(8-($n%8)));
else $lng = 0;
$text = str_pad($text, $lng, ' ');
$text = $this->_str2long($text);
//Initialization vector: IV
if($this->cbc == 1) {
$cipher[0][0] = time();
$cipher[0][1] = (double)microtime()*1000000;
}
$a = 1;
for($i = 0; $i<count($text); $i+=2) {
if($this->cbc == 1) {
//$text with last ciphertext XOR
//$text is XORed with the previous ciphertext
$text[$i] ^= $cipher[$a-1][0];
$text[$i+1] ^= $cipher[$a-1][1];
}
$cipher[] = $this->block_encrypt($text[$i],$text[$i+1]);
$a++;
}
$output = "";
for($i = 0; $i<count($cipher); $i++) {
$output .= $this->_long2str($cipher[$i][0]);
$output .= $this->_long2str($cipher[$i][1]);
}
return base64_encode($output);
}
//decipher
function decrypt($text) {
$plain = array();
$cipher = $this->_str2long(base64_decode($text));
if($this->cbc == 1)
$i = 2; //Message start at second block
else
$i = 0; //Message start at first block
for($i; $i<count($cipher); $i+=2) {
$return = $this->block_decrypt($cipher[$i],$cipher[$i+1]);
//Xor Linkage of $return and ciphertext from the last two blocks or sections
//XORed $return with the previous ciphertext
if($this->cbc == 1)
$plain[] = array($return[0]^$cipher[$i-2],$return[1]^$cipher[$i-1]);
else //EBC Mode
$plain[] = $return;
}
for($i = 0; $i<count($plain); $i++) {
$output .= $this->_long2str($plain[$i][0]);
$output .= $this->_long2str($plain[$i][1]);
}
return $output;
}
//Prepare the key to decrypt ver / front
function key_setup($key) {
if(is_array($key))
$this->key = $key;
else if(isset($key) && !empty($key))
$this->key = $this->_str2long(str_pad($key, 16, $key));
else
$this->key = array(0,0,0,0);
}
//Performs a benchmark
function benchmark($length=1000) {
//1000 Byte String
$string = str_pad("", $length, "text");
//Key-Setup
$start1 = time() + (double)microtime();
$xtea = new XTEA("key");
$end1 = time() + (double)microtime();
//Encryption
$start2 = time() + (double)microtime();
$xtea->Encrypt($string);
$end2 = time() + (double)microtime();
echo "Encrypting ".$length." bytes: ".round($end2-$start2,2)." seconds (".round($length/($end2-$start2),2)." bytes/second)<br>";
}
//verify the correct implementation of the blowfish algorithm
function check_implementation() {
$xtea = new XTEA("");
$vectors = array(
array(array(0x00000000,0x00000000,0x00000000,0x00000000), array(0x41414141,0x41414141), array(0xed23375a,0x821a8c2d)),
array(array(0x00010203,0x04050607,0x08090a0b,0x0c0d0e0f), array(0x41424344,0x45464748), array(0x497df3d0,0x72612cb5)),
);
//Correct implementation?
$correct = true;
//Test vectors, see http://www.schneier.com/code/vectors.txt
foreach($vectors AS $vector) {
$key = $vector[0];
$plain = $vector[1];
$cipher = $vector[2];
$xtea->key_setup($key);
$return = $xtea->block_encrypt($vector[1][0],$vector[1][1]);
if((int)$return[0] != (int)$cipher[0] || (int)$return[1] != (int)$cipher[1])
$correct = false;
}
return $correct;
}
/***********************************
Some internal functions
***********************************/
function block_encrypt($y, $z) {
$sum=0;
$delta=0x9e3779b9;
/* start cycle */
for ($i=0; $i<32; $i++)
{
$y = $this->_add($y,
$this->_add($z << 4 ^ $this->_rshift($z, 5), $z) ^
$this-> _add($sum, $this->key[$sum & 3]));
$sum = $this->_add($sum, $delta);
$z = $this->_add($z,
$this->_add($y << 4 ^ $this->_rshift($y, 5), $y) ^
$this->_add($sum, $this->key[$this->_rshift($sum, 11) & 3]));
}
/* end cycle */
$v[0]=$y;
$v[1]=$z;
return array($y,$z);
}
function block_decrypt($y, $z) {
$delta=0x9e3779b9;
$sum=0xC6EF3720;
$n=32;
/* start cycle */
for ($i=0; $i<32; $i++)
{
$z = $this->_add($z,
-($this->_add($y << 4 ^ $this->_rshift($y, 5), $y) ^
$this->_add($sum, $this->key[$this->_rshift($sum, 11) & 3])));
$sum = $this->_add($sum, -$delta);
$y = $this->_add($y,
-($this->_add($z << 4 ^ $this->_rshift($z, 5), $z) ^
$this->_add($sum, $this->key[$sum & 3])));
}
/* end cycle */
return array($y,$z);
}
function _rshift($integer, $n) {
// convert to 32 bits
if (0xffffffff < $integer || -0xffffffff > $integer) {
$integer = fmod($integer, 0xffffffff + 1);
}
// convert to unsigned integer
if (0x7fffffff < $integer) {
$integer -= 0xffffffff + 1.0;
} elseif (-0x80000000 > $integer) {
$integer += 0xffffffff + 1.0;
}
// do right shift
if (0 > $integer) {
$integer &= 0x7fffffff; // remove sign bit before shift
$integer >>= $n; // right shift
$integer |= 1 << (31 - $n); // set shifted sign bit
} else {
$integer >>= $n; // use normal right shift
}
return $integer;
}
function _add($i1, $i2) {
$result = 0.0;
foreach (func_get_args() as $value) {
// remove sign if necessary
if (0.0 > $value) {
$value -= 1.0 + 0xffffffff;
}
$result += $value;
}
// convert to 32 bits
if (0xffffffff < $result || -0xffffffff > $result) {
$result = fmod($result, 0xffffffff + 1);
}
// convert to signed integer
if (0x7fffffff < $result) {
$result -= 0xffffffff + 1.0;
} elseif (-0x80000000 > $result) {
$result += 0xffffffff + 1.0;
}
return $result;
}
//Einen Text in Longzahlen umwandeln
//Covert a string into longinteger
function _str2long($data) {
$n = strlen($data);
$tmp = unpack('N*', $data);
$data_long = array();
$j = 0;
foreach ($tmp as $value) $data_long[$j++] = $value;
return $data_long;
}
//Longzahlen in Text umwandeln
//Convert a longinteger into a string
function _long2str($l){
return pack('N', $l);
}
}
?>
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