Wired – As contact tracing plans firm up, the tech giants are sharing new details for their framework—and a potential app interface.”…The two companies [Google and Apple] have published sample user interface screenshots for the first time as well. As Google and Apple first outlined last month, their Covid-19 exposure notification system transmits unique, rotating codes from phones via their Bluetooth radios based on cryptographic keys that change daily. They not only keep a log of the last two weeks of your codes, but also listen for the codes broadcast by others. If two people running the app spend a certain amount of time in proximity—say, 10 minutes within six feet, or whatever health care agencies dictate—their phones will both record each others’ Bluetooth codes. If one of them later receives a positive Covid-19 diagnosis, they can choose to upload all of their keys from the last two weeks to the app’s server, which will then send those keys out to the phones of all the other users in their region. Those phones will then check if the codes they’ve recorded from other nearby users can be generated from those keys. If you get a match, the app will show a message that you’ve potentially been exposed to Covid-19 and caution you to self-quarantine or get tested…”