protected function prepareSignCommand()
    {
        $command = $this->zendsignPath;

        // add license path
        $command .= ' ' . $this->getLicenseTemplatePath();

        // add result file path
        $command .= ' ' . $this->outputFile;

        // add key path
        $command .= ' ' . $this->privateKeyPath;

        $this->zendsignCommand = $command;

        return $command;
    }