DRM can be used to uniquely identify your device. An example of using DRM for tracking in Android:
> When a device uses DRM for the first time, a device provisioning occurs, which means that the device will obtain a unique certificate and it will be stored in the DRM service of the device ... This provisioning profile has a unique ID, and you can obtain it with a simple call. This ID is not only the same on all apps, but also it is the same for all users of the device. So a guest account, for example, will also obtain the same ID, as opposed to the ANDROID_ID.
> When a device uses DRM for the first time, a device provisioning occurs, which means that the device will obtain a unique certificate and it will be stored in the DRM service of the device ... This provisioning profile has a unique ID, and you can obtain it with a simple call. This ID is not only the same on all apps, but also it is the same for all users of the device. So a guest account, for example, will also obtain the same ID, as opposed to the ANDROID_ID.
Source: https://beltran.work/blog/2018-03-27-device-unique-id-androi...