public function signFile(
        $filename,
        $signedFile = null,
        $mode = self::SIGN_MODE_NORMAL,
        $armor = self::ARMOR_ASCII,
        $textmode = self::TEXT_RAW
    ) {
        return $this->_sign(
            $filename,
            true,
            $signedFile,
            $mode,
            $armor,
            $textmode
        );
    }