There have recently been several proposalsfor pseudonymous contact tracing, including from Apple and Google. To both cryptographers and privacy advocates, this might seem the obvious way to protect public health and privacy at the same time. Meanwhile other cryptographers have been pointing out some of the flaws.
There are also real systems being built by governments. Singapore has already deployedand open-sourced one that uses contact tracing based on bluetooth beacons. Most of the academic and tech industry proposals follow this strategy, as the “obvious” way to tell who’s been within a few metres of you and for how long. The UK’s National Health Service is working on one too, and I’m one of a group of people being consulted on the privacy and security.
But contact tracing in the real world is not quite as many of the academic and industry proposals assume.
First, it isn’t anonymous. Covid-19 is a notifiable disease so a doctor who diagnoses you must inform the public health authorities, and if they have the bandwidth they call you and ask who you’ve been in contact with. They then call your contacts in turn. It’s not about consent or anonymity, so much as being persuasive and having a good bedside manner.