private function checkKey()
{
if (empty($this->key) || empty($this->authentication)) {
$key = $this->secureRandomKey();
$message = 'No binary key provided to encrypt/decrypt data.';
if ($key !== null) {
$message .= sprintf(" For example: base64_decode('%s')", base64_encode($key));
}
throw new RuntimeException($message);
}
}