This is very close, except for the part I highlighted. If you test positive, you can volunteer to upload your own keys. Healthy people's keys are never uploaded. Your phone uploads "these are the keys I've been broadcasting over the past 14 days".
Then everyone else can look at the "infected keys" database, and on-device determine if they've seen any of those keys in the past 14 days.
Page 8: https://covid19-static.cdn-apple.co...otification-CryptographySpecificationv1.1.pdf
I agree that Stromos is absolutely incorrect.
Ahh quite right, I hadn't actually read the API documentation, I was just theorizing how this could be done in a truly anonymous manner. I am going to edit my post to reflect my inaccuracies. Thanks for the flag!