title: Generating unique id in android (UUID)
body: <p>for months I've been using a class to generate a UUID that was solid between reintalls. My app is about discounts so I rely on this UUID to limit the number of coupons per device.</p>
  
  <pre><code>protected void getDeviceId(){
      try {
          Context context = cordova.getActivity().getApplicationContext();
          TelephonyManager tm = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
  
          String uuid;
          String androidID = Secure.getString(context.getContentResolver(), Secure.ANDROID_ID);
          String deviceID = tm.getDeviceId();
          String simID = tm.getSimSerialNumber();
  
          if ("9774d56d682e549c".equals(androidID) || androidID == null) {
              androidID = "";
          }
  
          if (deviceID == null) {
              deviceID = "";
          }
  
          if (simID == null) {
              simID = "";
          }
  
          uuid = androidID + deviceID + simID;
          uuid = String.format("%32s", uuid).replace(' ', '0');
          uuid = uuid.substring(0, 32);
          uuid = uuid.replaceAll("(\\w{8})(\\w{4})(\\w{4})(\\w{4})(\\w{12})", "$1-$2-$3-$4-$5");
  
          this.callbackContext.success(uuid);
      }catch(Exception e ) {
          this.callbackContext.error("Exception occurred: ".concat(e.getMessage()));
      }
  }
  </code></pre>
  
  <p>That's the core of how I generate my uuid. The thing is this weekend someone with an XT1032 and android 5.1 was able to regenerate different UUIDs after each installation of the app, getting free coupons. This method that I use can be tricked somehow? Maybe with a rooted phone? I'm shooting in the blind. I need to be able to create reliable UUIDs between installations.</p>