Hansel and Gretel and the Virus: Privacy Conscious Contact Tracing. (arXiv:2101.03241v1 [cs.CR])

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.