public function getHeaders()
    {
        $digest = Klarna::digest(
            Klarna::colon(
                $this->config['eid'],
                $this->params['currency'],
                $this->config['secret']
            )
        );

        return array(
            "Accept: {$this->accept}",
            "Authorization: xmlrpc-4.2 {$digest}"
        );
    }