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);
}
/**
* 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;
}
