Considerable and interesting, below an intro, very relevant, much more at the link.
Deploying Decentralized, Privacy-Preserving Proximity Tracing
By Carmela Troncoso, Dan Bogdanov, Edouard Bugnion, Sylvain Chatel, Cas Cremers, Seda Gürses, Jean-Pierre Hubaux, Dennis Jackson, James R. Larus, Wouter Lueks, Rui Oliveira, Mathias Payer, Bart Preneel, Apostolos Pyrgelis, Marcel Salathé, Theresa Stadler, Michael Veale
Communications of the ACM, September 2022, Vol. 65 No. 9, Pages 48-57 10.1145/3524107
Contact tracing is a time-proven technique for breaking infection chains in epidemics. Public health officials interview those who come in contact with an infectious agent, such as a virus, to identify exposed, potentially infected people. These contacts are notified that they are at risk and should take efforts to avoid infecting others—for example, by going into quarantine, taking a test, wearing a mask continuously, or taking other precautionary measures.
n March 2020, as the first wave of the COVID-19 pandemic was peaking, traditional manual contact tracing efforts in many countries were overwhelmed by the sheer volume of cases; by the rapid speed at which SARS-CoV-2 spread; and by the large fraction of asymptomatic, yet infectious, individuals.
Many people quickly and independently proposed using ubiquitous smartphones to implement digital contact tracing (DCT). In this new approach, an app on a user's phone could record contacts (encounters with other people) of sufficient time duration. If a physically close contact was diagnosed as infected, the app could inform the phone's potentially infected user. The envisioned technology would complement manual contact tracing by notifying people faster; reducing the burden on trained contract tracers; increasing scalability; and finding anonymous contacts, such as those in public spaces like shops and transportation, who would be otherwise unreachable through traditional systems. ...>
