public static function decrypt($encryptionKey, $encryptedString, $blockType = 'CBC', $urlSafe = false)
{
if ($urlSafe) {
$data = Base64URLSafe::urlsafe_b64decode($encryptedString);
} else {
$data = base64_decode($encryptedString);
}
switch ($blockType) {
case 'CBC':
$cipher = new Rijndael(Rijndael::MODE_CBC);
$cipher->setKey($encryptionKey);
// Split the IV from the ciphertext
$iv = substr($data, 0, $cipher->getBlockLength() >> 3);
$cipherText = substr($data, $cipher->getBlockLength() >> 3, strlen($encryptedString));
$cipher->setIV($iv);
break;
case 'ECB':
$cipher = new Rijndael(Rijndael::MODE_ECB);
$cipher->setKey($encryptionKey);
$cipherText = $data;
break;
default:
throw new \Exception('Unknown encryption blocktype: ' . $blockType, 500);
break;
}
return $cipher->decrypt($cipherText);
}
/**
* @group github451
*/
public function testKeyPaddingRijndael()
{
// this test case is from the following URL:
// https://web.archive.org/web/20070209120224/http://fp.gladman.plus.com/cryptography_technology/rijndael/aesdvec.zip
$aes = new Rijndael();
$aes->setPreferredEngine($this->engine);
$aes->disablePadding();
$aes->setKey(pack('H*', '2b7e151628aed2a6abf7158809cf4f3c762e7160'));
// 160-bit key. Valid in Rijndael.
//$this->_checkEngine($aes); // should only work in internal mode
$ciphertext = $aes->encrypt(pack('H*', '3243f6a8885a308d313198a2e0370734'));
$this->assertEquals($ciphertext, pack('H*', '231d844639b31b412211cfe93712b880'));
}
/**
* Sets the key.
*
* Rijndael supports five different key lengths, AES only supports three.
*
* @see Crypt_Rijndael:setKey()
* @see setKeyLength()
* @access public
* @param string $key
*/
function setKey($key)
{
parent::setKey($key);
if (!$this->explicit_key_length) {
$length = strlen($key);
switch (true) {
case $length <= 16:
$this->key_length = 16;
break;
case $length <= 24:
$this->key_length = 24;
break;
default:
$this->key_length = 32;
}
$this->_setEngine();
}
}
/**
* Decrypt the encrypted string using Rijndael algorithm
*
* @param string $encryptedString Encrypted string
* @param string $key Paytm Merchant Key
* @return string Plain text
*/
public function decryptString($encryptedString, $key)
{
$cipher = new Rijndael();
$cipher->setKey($key);
$cipher->iv = $this->iv;
$encryptedString = base64_decode($encryptedString);
$plaintext = $cipher->decrypt($encryptedString);
if (!$plaintext) {
throw new InvalidResponseException("Invalid checksum.");
}
return $plaintext;
}
