protected static function plainDecrypt($ciphertext, $key, $iv, $cipherMethod)
{
Core::ensureConstantExists('OPENSSL_RAW_DATA');
Core::ensureFunctionExists('openssl_decrypt');
$plaintext = \openssl_decrypt($ciphertext, $cipherMethod, $key, OPENSSL_RAW_DATA, $iv);
if ($plaintext === false) {
throw new Ex\EnvironmentIsBrokenException('openssl_decrypt() failed.');
}
return $plaintext;
}