Interesting - every version I've looked at to date still creates a form of "infected list". You could try bloom filters but at risk of many false positives, at

Interesting - every version I've looked at to date still creates a form of "infected list". You could try bloom filters but at risk of many false positives, at a time you really don't want false positives. Looking at the Apple + Google spec though, this is happening - see https://covid19-static.cdn-apple.com/applications/covid19/current/static/contact-tracing/pdf/ExposureNotification-CryptographySpecificationv1.2.pdf https://covid19-static.cdn-apple.com/applications/covid19/cu... I can't really see a way to avoid creating an "infected tokens" list, if you want a decentralised approach where the uninfected are not interacting with the protocol on an ongoing basis as well. The UK approach (centralised) was different though, as it was based on the infected person telling the server "who" (based on the tokens) it saw, and they take the steps to notify those users by decrypting the tokens etc, and working out who needs notified. In the decentralised apps, your phone squawks a changing "identifier", everyone stores the squawks they hear, and periodically checks their list of squawks heard to see if any are flagged on the infected list.