That's not what "contacts" and "centralised" means in the context of the app.bob sterman wrote: ↑Wed Jun 03, 2020 1:42 pmThat will go down well!
Passing on contact information for people you've actually had physical contact with is one thing. That is something quite different.
The wired link says "when people say they may have coronavirus symptoms the data about the number of devices they have been in contact with, plus the signal strength and signal duration, are transmitted back to a central, anonymised database".
The 3blue1brown link explains the operation of an app which uploads all the recent output strings from a covid-positive user to a central database, so that other users' phones can check if they've been in contact with a covid-positive user's phone. i.e. the contact checking is decentralised, because it takes place on a user's phone and the user gets an alert directly.
The alternative is that a user's phone uploads all the output strings it has received to a central database, the contact checking is done there, and the alerts are sent back to phones whose apps picked up output strings which match covid-positive cases.
Article which is nearly a month old: https://www.bbc.com/news/technology-52355028
Both kinds of app need a "central" database even if the contact checking is done on your own phone, and neither kind of app means "the phone numbers saved in your address book" when it refers to "contacts".