Technology enabled contact tracing seems like a rational response to the current pandemic. However, both the characteristics of SARS-CoV-2 and the unintended consequences of implementing some of the suggested technologies suggest that a coordinated social response is a better road forward.
Using the Alice and Bob for metaphors for relationships on the web only works when Alice and Bob are actually peers with equal say in their relationship.
A proposal for a Legal Reference Token (LRT) as a software token to connect business, legal and technical requiremeents.
If you want some high level guidance on privacy, this might qualify.
Privacy in the design of sites is not about efficiency. It's about resiliency. Building a site that meets user privacy expectations will lead to long term and continuing engagement.