john_payette

indeed this news was already published a few days ago.

This tag has an U1 chip using Ultra Wide Band (UWB) which means that iPhones 11 and above also equipped with those chips will be able to locate those tags from 80m away with a +/-30cm accuracy. U1 UWB uses short pulses at 6.24GHz and 8.2GHz and positioning is done by combining time of flight (ToF) and angle of arrival (AoA).

DP-3T admits now that the best solution is the Apple-Google one. They greatly contributed to the design of the A-G solution so kudos to them. After reviewing this critical review of DP-3T, the only attack I see that applies to the Google-Apple solution is the replay attack. It can be fixed easily by the solution proposed by Prof. Serge Vaudenay of EPFL in Section 4.4 of https://eprint.iacr.org/2020/399.pdf. In a nutshell, send a tag along the ephemeral ID. This tag would be a message authentication code (MAC) computed with the ephemeral ID and a coarse timestamp of when it was sent using the sender's key, SKt. When Apple-Google sends out the SKt keys of the infected people to everybody, recipients will go through the ephemeral IDs they saw to look for matches. When there's a match, the tag will also be checked, i.e. does the tag I compute based on the timestamp when I received the ephemeral ID match the tag I received. If yes, then it was sent by this infected person. Otherwise, it's a replay attack and should be discarded.

I agree. Ideally, the code will be embedded in the Android source code, which is open source. But more likely it will be an update of the Google Play Services, closed-source... But the Cloud code should definitely be open-source. We can count on Google for that.

Here's a comparison of the Apple-Google solution vs. the PEPP-PT project using this DP-3T approach: https://medium.com/@legfranck/the-good-and-the-bad-of-apple-...