A Needle in the Haystack - Delay Based User Identification in Cellular Networks

In this work, we discuss a technique for identifying users in cellular networks that exploits the effect that RRC state machine transitions have on the measured round-trip time of mobile devices. Our preliminary experiments performed in a controlled environment, show that it is possible to leverage popular real-time messaging apps, such as Facebook, WhatsApp and Viber, to trigger an observable delay pattern on a user's device, and use it to identify the device.