Sandstorm wrote: Tue Oct 13, 2020 2:51 pm
Saint wrote: Tue Oct 13, 2020 2:16 pm
Whether these apps REALLY work is open for debate - we been round the houses on here ad nauseum the accuracy of Bluetooth beaconing - but I'm damned sure that I won't be the reason for them not working, and I would hope that other people would be of a similar mindset
How does the App work? I went to a busyish restaurant on Friday and turned on my App. It started scanning, but found nothing.
Does that mean I'm the only one who has it? Or it was just scanning for UFO transmissions from Pluto?
It won't actively report on whether any other users nearby have the app switched on - it's simply telling you that it's working and scanning. This becomes more obvious (and important to you) if you have multiple apps (i.e. you're moving between different countries), as only one app can be scanning at a time. So when I went to Venice I disabled HS and enabled Immuni. On landing back at Heathrow I disabled Immuni and re-enabled NHS. I'll uninstall Immuni in a week or so once any realistic chance of me needing to be notified of coming into contact with an Italian who's tested positive has finished.
Behind the scenes, the way the API works if I;ve understood the documentation correctly is that each phone generates a random identifier when the app is installed. That is shared with other devices once a threshold of Bluetooth strength vs time is met with a nearby device. The phone individually stores those records. At the same time the phone also stores the record of venue QR checkins.
if you enter a positive test result into the app, it then effectively broadcast that test result to the ids it's collected, and the QR record of date/time as a general broadcast. Other devices then either pick up the direct broadcast of their device id, and/or check their QR history. Any time there's a positive match it alerts that you MAY have been in contact. At an individual level, you can;t be identified, and because it's not being collated centrally you can;t be tracked either. The only way they know much about the positive reporting on the QR code stuff is the it;s a general broadcast - so the can see how many alerts are related to a QR code - but even then they don't know who