public String authToken(String projectKeyId, String secretKey, String keyArray) throws Exception {
    String message = "projectId="+projectKeyId+"&visitUserId="+keyArray;
    Mac hmac = Mac.getInstance("HmacSHA256");
    hmac.init(new SecretKeySpec(secretKey.getBytes("UTF-8"), "HmacSHA256"));
    byte[] signature = hmac.doFinal(message.getBytes("UTF-8"));
    return Hex.encodeHexString(signature);