TelegramEncryption.php

<?php
class TelegramEncryption
{
	public $key;
	public $iv;
	public $cipherText;
	public $plainText;
	public $debug;

	public function __construct($key, $iv, $cipherText, $plainText, $debug = false)
	{
		$this->key = $key;
		$this->iv = $iv;
		$this->cipherText = $cipherText;
		$this->plainText = $plainText;
		$this->debug = $debug;
	}

	public function decrypt()
	{
		$decrypted = $this->IGE256Decrypt();
		if($this->hexArrayToString($decrypted) == $this->hexArrayToString($this->plainText))
		{
			return true;
		}
		else
		{
			return false;
		}
	}

	public function IGE256Decrypt()
	{
		$key = $this->key;
		$IV = $this->iv;
		$message = $this->cipherText;

		$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);

		$xPrev = array_slice($IV, 0, $blockSize);
		$yPrev = array_slice($IV, $blockSize, count($IV));

		$decrypted = array();

		for($i = 0; $i < count($message); $i += $blockSize)
		{
			$x = array_slice($message, $i, $i + $blockSize);
			$this->debugLog("x: " . $this->hexArrayToString($x) . "\n");

			$yXOR = $this->exor($x, $yPrev);
			$this->debugLog("yPrev: " . $this->hexArrayToString($yPrev) . "\n");
			$this->debugLog("yXOR: " . $this->hexArrayToString($yXOR) . "\n");

			$yFinal = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, hex2bin($this->hexArrayToString($key)), hex2bin($this->hexArrayToString($yXOR)), MCRYPT_MODE_ECB);
			$yFinal = bin2hex($yFinal);
			$yFinal = $this->hexStringToArray($yFinal);
			$yFinal = array_pad($yFinal, count($xPrev), 0);
			$this->debugLog("yFinal: " . $this->hexArrayToString($yFinal) . "\n");

			$y = $this->exor($yFinal, $xPrev);
			$this->debugLog("xPrev: " . $this->hexArrayToString($xPrev) . "\n");
			$this->debugLog("y: " . $this->hexArrayToString($y) . "\n\n");

			$xPrev = $x;
			$yPrev = $y;

			$decrypted = array_merge($decrypted, $y);
		}
		return $decrypted;
	}

	public function debugLog($message)
	{
		if($this->debug)
		{
			echo $message;
		}
	}

	public function exor($array1, $array2)
	{
		$res = array();

		$len = (count($array1) <= count($array2)) ? count($array2) : count($array1);
		$res = array_pad($res, $len, 0);

		$array1 = array_pad($array1, $len, 0);
		$array2 = array_pad($array2, $len, 0);

		$i = 0;
		foreach($array1 as $byte)
		{
			$byte = dechex($byte);
			$byte2 = dechex($array2[$i++]);

			$byte = $this->hexDecSigned($byte);
			$byte2 = $this->hexDecSigned($byte2);

			$hex = $byte ^ $byte2;
			$hex = str_pad($hex, 2, "0", STR_PAD_LEFT);

			$res[$i - 1] = strtoupper($hex);
		}
		return $res;
	}

  //http://php.net/manual/en/function.hexdec.php#97172
	public function hexDecSigned($hex)
	{
		// ignore non hex characters
		$hex = preg_replace("/[^0-9A-Fa-f]/", "", $hex);

		// converted decimal value:
		$dec = hexdec($hex);

		// maximum decimal value based on length of hex + 1:
		//   number of bits in hex number is 8 bits for each 2 hex -> max = 2^n
		//   use 'pow(2,n)' since '1 << n' is only for integers and therefore limited to integer size.
		$max = pow(2, 4 * (strlen($hex) + (strlen($hex) % 2)));

		// complement = maximum - converted hex:
		$_dec = $max - $dec;

		// if dec value is larger than its complement we have a negative value (first bit is set)
		return $dec > $_dec ? -$_dec : $dec;
	}

	public function hexStringToArray($hexString)
	{
		$finalArray = array();

		for($i = 0; $i < strlen($hexString); $i += 2)
		{
			$hexPart = substr($hexString, $i, 2);
			if(strlen($hexPart) == 1)
			{
				$hexPart = "0{$hexPart}";
			}
			$finalArray[] = $this->hexDecSigned($hexPart);
		}
		return $finalArray;
	}

	public function hexArrayToString($array)
	{
		$string = "";
		foreach($array as $hex)
		{
			$hex &= 0xFF;
			$string .= strtoupper(str_pad(dechex($hex), 2, "0", STR_PAD_LEFT));
		}
		return $string;
	}
}

TelegramTests.php

<?php
include_once("./TelegramEncryption.php");

//data from http://www.links.org/files/openssl-ige.pdf
$keys = array(
	array(0x00, 0x01, 0x02, 0x03,
		0x04, 0x05, 0x06, 0x07,
		0x08, 0x09, 0x0A, 0x0B,
		0x0C, 0x0D, 0x0E, 0x0F),

	array(0x54, 0x68, 0x69, 0x73,
		0x20, 0x69, 0x73, 0x20,
		0x61, 0x6E, 0x20, 0x69,
		0x6D, 0x70, 0x6C, 0x65)
);

$ivs = array(
	array(0x00, 0x01, 0x02, 0x03,
		0x04, 0x05, 0x06, 0x07,
		0x08, 0x09, 0x0A, 0x0B,
		0x0C, 0x0D, 0x0E, 0x0F,
		0x10, 0x11, 0x12, 0x13,
		0x14, 0x15, 0x16, 0x17,
		0x18, 0x19, 0x1A, 0x1B,
		0x1C, 0x1D, 0x1E, 0x1F),

	array(0x6D, 0x65, 0x6E, 0x74,
		0x61, 0x74, 0x69, 0x6F,
		0x6E, 0x20, 0x6F, 0x66,
		0x20, 0x49, 0x47, 0x45,
		0x20, 0x6D, 0x6F, 0x64,
		0x65, 0x20, 0x66, 0x6F,
		0x72, 0x20, 0x4F, 0x70,
		0x65, 0x6E, 0x53, 0x53)
);

$plainTexts = array(
	array(0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00),

	array(0x99, 0x70, 0x64, 0x87,
		0xA1, 0xCD, 0xE6, 0x13,
		0xBC, 0x6D, 0xE0, 0xB6,
		0xF2, 0x4B, 0x1C, 0x7A,
		0xA4, 0x48, 0xC8, 0xB9,
		0xC3, 0x40, 0x3E, 0x34,
		0x67, 0xA8, 0xCA, 0xD8,
		0x93, 0x40, 0xF5, 0x3B)
);

$cipherTexts = array(
	array(0x1A, 0x85, 0x19, 0xA6,
		0x55, 0x7B, 0xE6, 0x52,
		0xE9, 0xDA, 0x8E, 0x43,
		0xDA, 0x4E, 0xF4, 0x45,
		0x3C, 0xF4, 0x56, 0xB4,
		0xCA, 0x48, 0x8A, 0xA3,
		0x83, 0xC7, 0x9C, 0x98,
		0xB3, 0x47, 0x97, 0xCB),

	array(0x4C, 0x2E, 0x20, 0x4C,
		0x65, 0x74, 0x27, 0x73,
		0x20, 0x68, 0x6F, 0x70,
		0x65, 0x20, 0x42, 0x65,
		0x6E, 0x20, 0x67, 0x6F,
		0x74, 0x20, 0x69, 0x74,
		0x20, 0x72, 0x69, 0x67,
		0x68, 0x74, 0x21, 0x0A)
);

$results = array();
for($i = 0; $i < count($keys); $i++)
{
	$key = $keys[$i];
	$iv = $ivs[$i];
	$cipherText = $cipherTexts[$i];
	$plainText = $plainTexts[$i];
	$debug = true;

	$telegram = new TelegramEncryption($key, $iv, $cipherText, $plainText, $debug);
	$results[] = $telegram->decrypt();
}

foreach($results as $index => $res)
{
	$msg = "Test #{$index}: ";
	if($res)
		$msg .= "Success!";
	else
		$msg .= "Failure :(";

	echo "{$msg}\n";
}