protected function _computeFinalKey($key1, $key2, $data)
    {
        if (mb_orig_strlen($data) < 8) {
            Daemon::$process->log(get_class($this) . '::' . __METHOD__ . ' : Invalid handshake data for client "' . $this->addr . '"');
            return false;
        }
        return md5($this->_computeKey($key1) . $this->_computeKey($key2) . mb_orig_substr($data, 0, 8), true);
    }