TimeStampRequest request = createTimeStampRequest(data);
        byte[] requestData = request.getEncoded();

        // POST query to TSA
        HttpURLConnection con;
        URL tspUrl = new URL(Config.TSP_URL);
        con = (HttpURLConnection) tspUrl.openConnection();
        con.setRequestMethod("POST");
        con.setDoOutput(true);
        con.setRequestProperty("Content-Type", "application/timestamp-query");
        OutputStream reqStream = con.getOutputStream();
        reqStream.write(requestData);
        reqStream.close();

        InputStream responseStream = con.getInputStream();
        byte[] bytes = IOUtils.toByteArray(responseStream);

        TimeStampResponse response = new TimeStampResponse(bytes);