This topic describes how to use Message Queuing Telemetry Transport (MQTT) to implement dynamic registration for a directly connected device.

IoT Platform supports multiple authentication methods for devices. For more information, see Authenticate a device.

IoT Platform allows you to implement dynamic registration by using MQTT. For more information about dynamic registration, see Dynamically register a directly connected device based on the unique-certificate-per-product authentication.

This topic use sample code that is written in Java as an example.


The following steps that are specified in the Unique-certificate-per-product authentication topic are performed:

  1. Create a product.
  2. Enable dynamic registration.
  3. Add a device.
  4. Burn the device SDK on the production line.

Configure the pom.xml file

Add the following dependencies to the pom.xml file to import SDKs.



Sample code

  • If a device is not activated, you can repeat dynamic registration for the device. Each time you obtain a different DeviceSecret. Ensure that the device is dynamically registered once and the DeviceSecret that you obtain is persisted on the device.
  • If an activated device needs to be dynamically registered again, you must reset the device in IoT Platform. You can call the ResetThing operation to reset the device.
 * Copyright © 2019 Alibaba. All rights reserved.
package com.aliyun.iot.demo;

import java.nio.charset.StandardCharsets;
import java.util.Random;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;


 * Implement dynamic registration for a device. 
public class DynamicRegisterByMqtt {

    // The ID of the region where your product resides. 
    private static String regionId = "cn-shanghai";

    // Specify an encyrption algorithm. Valid values: hmacmd5, hmacsha1, and hmacsha256.The value that you specify must be the same as that for the signmethod parameter.
    private static final String HMAC_ALGORITHM = "hmacsha1";

    // The topic that receives device certificates from IoT Platform. Use the topic without any changes. You do not need to create or subscribe to the topic.
    private static final String REGISTER_TOPIC = "/ext/register";

     * Implement dynamic registration.
     * @param productKey The key of a product.
     * @param productSecret The secret of the product.
     * @param deviceName The name of a device.
     * @throws Exception
    public void register(String productKey, String productSecret, String deviceName) throws Exception {

        // The endpoint of the authentication service. Only Transport Layer Security (TLS) is available.
        String broker = "ssl://" + productKey + ".iot-as-mqtt." + regionId + "";

        // The client ID. We recommend that you use the MAC address or SN of the device. The client ID can be a maximum of 64 characters in length.
        String clientId = productKey + "." + deviceName;

        // Obtain a random value.
        Random r = new Random();
        int random = r.nextInt(1000000);

        // The value of the securemode parameter is 2 and cannot be changed. The value 2 indicates that TLS is applied. The signmethod parameter specifies an encryption algorithm.
        String clientOpts = "|securemode=2,authType=register,signmethod=" + HMAC_ALGORITHM + ",random=" + random + "|";

        // The ID of an MQTT client.
        String mqttClientId = clientId + clientOpts;

        // The usename that the MQTT client uses to connect to the endpoint.
        String mqttUsername = deviceName + "&" + productKey;

        // The signature that the MQTT client uses to connect to the endpoint.
        JSONObject params = new JSONObject();
        params.put("productKey", productKey);
        params.put("deviceName", deviceName);
        params.put("random", random);
        String mqttPassword = sign(params, productSecret);

        // Use an MQTT CONNECT packet for dynamic registration.
        connectMqtt(targetServer, mqttClientId, mqttUsername, mqttPassword);

     * Use an MQTT CONNECT packet to send a message about dynamic registration.
     * @param serverURL The endpoint for dynamic registration.
     * @param clientId The client ID.
     * @param username The username that the MQTT client uses.
     * @param password The password that the MQTT client uses.
    private void connect(String serverURL, String clientId, String username, String password) {
        try {
            MemoryPersistence persistence = new MemoryPersistence();
            MqttClient sampleClient = new MqttClient(serverURL, clientId, persistence);
            MqttConnectOptions connOpts = new MqttConnectOptions();
            connOpts.setMqttVersion(4);// MQTT 3.1.1.
            connOpts.setUserName(username);// The username.
            connOpts.setPassword(password.toCharArray());// The password.
            connOpts.setAutomaticReconnect(false); // Disable the automatic reconnection feature based on MQTT rules that are set for dynamic registration.
            System.out.println("----- register params -----");
            System.out.print("server=" + serverURL + ",clientId=" + clientId);
            System.out.println(",username=" + username + ",password=" + password);
            sampleClient.setCallback(new MqttCallback() {
                public void messageArrived(String topic, MqttMessage message) throws Exception {
                    // Print out only responses for dynamic registration.
                    if (REGISTER_TOPIC.equals(topic)) {
                        String payload = new String(message.getPayload(), StandardCharsets.UTF_8);
                        System.out.println("----- register result -----");

                public void deliveryComplete(IMqttDeliveryToken token) {

                public void connectionLost(Throwable cause) {
        } catch (MqttException e) {
            System.out.print("register failed: clientId=" + clientId);
            System.out.println(",username=" + username + ",password=" + password);
            System.out.println("reason " + e.getReasonCode());
            System.out.println("msg " + e.getMessage());
            System.out.println("loc " + e.getLocalizedMessage());
            System.out.println("cause " + e.getCause());
            System.out.println("excep " + e);

     * Generate a signature for dynamic registration.
     * @param params The required parameters that you use to generate a signature.
     * @param productSecret The secret of a product.
     * @return A string that includes a signature in the hex format.
    private String sign(JSONObject params, String productSecret) {

        // Sort request parameters in the alphabetical order.
        Set<String> keys = getSortedKeys(params);

        // Remove the sign and signMethod parameters.

        // Obtain the plaintext of the signature.
        StringBuffer buffer = new StringBuffer();
        for (String key : keyList) {

        // Generate a signature.
        String sign = encrypt(content.toString(), productSecret);
        System.out.println("sign content=" + content);
        System.out.println("sign result=" + sign);

        return sign;

     * Convert a JSON object to a set of key-value pairs.
     * @param json A JSON object to convert.
     * @return A set of key-value pairs that are converted from the JSON object.
    private Set<String> getSortedKeys(JSONObject json) {
        SortedMap<String, String> map = new TreeMap<String, String>();
        for (String key : json.keySet()) {
            String vlaue = json.getString(key);
            map.put(key, vlaue);
        return map.keySet();

     * Specify an encryption algorithm in the HMAC_ALGORITHM parameter.
     * @param content Plaintext.
     * @param secret An encryption key.
     * @return Ciphertext.
    private String encrypt(String content, String secret) {
        try {
            byte[] text = content.getBytes(StandardCharsets.UTF_8);
            byte[] key = secret.getBytes(StandardCharsets.UTF_8);
            SecretKeySpec secretKey = new SecretKeySpec(key, HMAC_ALGORITHM);
            Mac mac = Mac.getInstance(secretKey.getAlgorithm());
            return byte2hex(mac.doFinal(text));
        } catch (Exception e) {
            return null;

     * Convert a binary array to a hexadecimal string.
     * @param b A binary array.
     * @return A hexadecimal string.
    private String byte2hex(byte[] b) {
        StringBuffer sb = new StringBuffer();
        for (int n = 0; b ! = null && n < b.length; n++) {
            String stmp = Integer.toHexString(b[n] & 0XFF);
            if (stmp.length() == 1) {
        return sb.toString().toUpperCase();

    public static void main(String[] args) throws Exception {

        String productKey = "The productKey for your device";
        String productSecret = "The productSecret for your device";
        String deviceName = "The deviceName for your device";

        // Implement dynamic registration.
        DynamicRegisterByMqtt client = new DynamicRegisterByMqtt();
        client.register(productKey, productSecret, deviceName);

        // After dynamic registration is complete, store the deviceSecret on the device.