XTEA Encryption/Decryption

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?

<?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);
   }

}
?>

Code (markup):

 

Thanks to @xyph for the help. I think I'm almost there. I can get the encrypted string to change to base64 and it "looks" correct, but it still will not decrypt. Could I still be having an issue with the key string of "28d75A09ec63cxvxve870fad25e79b8c"? How do I change this into 16 characters? Below is my current code.

$ascii_string = '';
foreach( str_split($text,2) as $chunk ){ $ascii_string .= chr(hexdec($chunk)); }
$base64_string = base64_encode($ascii_string);

$xtea = new XTEA('28d75A09ec63c32b1e870fad25e79b8c');
$output =$xtea->Decrypt($base64_string);

Code (markup):

 

can you get XTEAs encryption method? If they're using $chunks as a home-made encryption similar to PGP or GnuPG
Then I dont see how you're going to decrypt it without their code strings. It's not Sha, Sha2, MD5 , PGP etc

it's easy to write encryption code in PHP , but the thing is you have to have the other keypair generated. If you are using unique key-pair generation then the code would've generated a keypair when the text file was created and there isn't one in another bit/string-chunk form.

So it will highly depend on if the encryption method was home-made by the creators.
Why not create your own?

Randomizing strings 1 - 0 and A - z and ! - )

and have it generate random characters for each letter, number and punctuation. and have each string length random.
so it could be something where
A = #$DFHGHJfjf$%$%
and the second time A appears is A= $$#%#@$DHF

and have it separate the strings with a encrypted white space
white_space = "$%^" example

so that the keypair is generated on the spot and doesn't exist anywhere else and can't be recalled.

Another sorta funny way to do it would be to use URL's as letters and numbers so that somebody opening an encrypted file sees nothing but run-on www.yoursite.comwww.yahoo.comwww.google.com etc full page that makes no sense.

 

crap. still lost and its not decrypting. This is where I'm at.

// convert HEX key to ASCII (working)
$ascii_key = hexToAscii('28d75A09ec63c32b1e870fad25e79b8c');
// (×Z	ìcÃ+‡*%盌


// convert XTEA encrypted HEX value to ASCII (working)
$ascii = hexToAscii($text);
// °ŸO´jÔAŽQäàœlª:6b½ÂدjÓðgÊ9#¨QÖ9@'XÕ}IÌ}ïŒ{![KP¢Èÿ—¢žî¥õu÷¨b‹Û9wgGâDþ[iØÍc¤Ü€S`ðËK‰L¨kV萙µGþ£©ÿmnLd¶Ê{+3@Fçèdj0/co£IÃîøÄ\:tCU)+1ª"Í:Eçr-po1ë×ΰ¶í[Á`ëÖ/®6èEç…| 40WŠ<=묀íbÈß )*[_©‘Å


// base64 encode ASCII value (working)
$base64_string = base64_encode($ascii);
// sJ9PtGrUQY5R5OCcbBGqOjZij70cwtivatPwFGfKORAjHKhR1jlAJ1jVfUnMfRLvjHshW0tQosj/l6Ke7qX1dfeoYovbOXdnR+JE/ltp2M1jpNyAU2Dwy0uJTKhrVuiQmbVH/qONFqkCA/9tbkxktsp7KzMYQEbn6GRqMC9jb6NJw+74xFw6dEMDAlUpKzGqIs06RedyLXBvMevXzrC27VvBYOsc1i+uNuhF54V8nSA0MFeKPD3rrICPC+1iyN8gKSpbFF+pkcU=


// decrypt XTEA encrypted value (FAILING)
$xtea = new XTEA($ascii_key);
$output = $xtea->Decrypt($base64_string);
echo  nl2br(htmlentities(stripslashes($output)));
// |üÑ61}¢BhžB`û”¢od¼4HÁÉ]sZÐ’=8ÿ€SúóØrh©òÌ$0nÄ'Ãw¾çhüÌ£TÆñwp}±Ì4-8EŸšl³¯0SéS¥åFŒ|Ù}I„ÚY;L(b‹-iSÖcž4!컁fôò¤”»ÑÙ[y4má—O"˜Eí&T‡Á'¸
œ7}ÎCVqòWC¢Þ_Ï&ƒšWn¨ðÏ}à›°„¢õ鍊ŽPÁÈ

Code (markup):

As you can see the last result is not a legible string. It should look like a bunch of parameters after a url. HELP!!