We sit down with Mikkel, exposure notification apps dutifully switched on, and talk about how such an application works. The Danish system, “SmitteStop”, uses Digital Privacy-Preserving Proximity Tracing. What does that even mean – how is the protocol defined, what is the mechanism by which privacy is preserved (and to which extent), and which role does the Google–Apple API play in the application?

Apart from the technical issues, we probe several issues on the fault line of technology and society. What are the alternatives to privacy-preserving exposure notification? E.g., could we do much more, and – to the extent that our phones already track everything and we share it freely – why aren’t we just using that information during a pandemic? What are the trade-offs between safety and liberty, is privacy a form of manslaughter, whom should we trust with our data, and how do different cultures around the globe manifest in deciding these tradeoffs?