The covid-19 app is capable of detecting who came into contact with who, how do they do it? I am trying to make something similar but I am unsure how they managed to get that information from the phones. I don't need the information to be private (like phone number), it could be something that only the government can make use of (like sim card number or MAC address. Is that possible?
I looked into Google Nearby and Wifi Direct... But as far as I understand it, it requires a handshake (covid19 app doesn't). I also looked into potentially making your phone into a hotspot and capturing wifi requests but I am not sure which library / API lets me do that.
Does anyone have know how this is done? I can't find a concrete answer anywhere, this seems to be actually impossible until I realized that the covid-19 app is doing it.