CallForge: Call Anonymity in Cellular Networks

In cellular networks, the locations of all subscribers are continously tracked even when they only passively carry their mobile devices with them. This privacy sensitive data can be an invaluable source of information, not only for benevolent parties. We therefore present CallForge, the concept of a location management scheme that preserves the subscribers’ anonymity – in many cases even while they participate in a phone call – as well as a theoretical analysis of the approach. CallForge improves on PathForge, a previously presented location management scheme, and as such is based on ID switching that we have combined with the emulation of a media break within a single call set-up procedure. We have analyzed and compared the anonymity of PathForge and CallForges, and shown that CallForge consistently provides superior anonymity. Callforge can be implemented entirely in the end device and run on existing network infrastructure without any modifications.