Hansel and Gretel and the Virus: Privacy Conscious Contact Tracing

Digital contact tracing has been proposed to support the health authorities in fighting the current Covid-19 pandemic. In this paper we propose two centralised protocols for digital contact tracing that, contrary to the common hypothesis that this is an inherent risk, do not allow (retroactive) tracking of the location of a device over time. The first protocol does not rely on synchronised clocks. The second protocol does not require a handshake between two devices, at the expense of relying on real-time communication with a central server. We stress that digital contact tracing is a form of technological solutionism that should be used with care, especially given the inherent mass surveillance nature of such systems.