SimpleSAML\Utils\Crypto::_aesEncrypt PHP Method

    private static function _aesEncrypt($data, $secret)
    {
        if (!is_string($data)) {
            throw new \InvalidArgumentException('Input parameter "$data" must be a string.');
        }
        if (!function_exists("openssl_encrypt")) {
            throw new \SimpleSAML_Error_Exception('The openssl PHP module is not loaded.');
        }
        $raw = defined('OPENSSL_RAW_DATA') ? OPENSSL_RAW_DATA : true;
        $key = openssl_digest($secret, 'sha256');
        $method = 'AES-256-CBC';
        $ivSize = 16;
        $iv = substr($key, 0, $ivSize);
        return $iv . openssl_encrypt($data, $method, $key, $raw, $iv);
    }