There has been a lot of talk about how contact tracing apps could help keep people safe from COVID-19 as countries try to move out of lockdown. There’s a really useful piece on Bloomberg News outlining the issues between various proposed models, including that being developed by Apple and Google.

Apple and Google even renamed their framework Exposure Notification, signaling that it doesn’t do true contact tracing, the process of tracking a virus from person to person. Instead, it lets individual smartphones keep track of which other handsets they’ve come close to by using Bluetooth wireless signals. If a person notifies the network they have tested positive for Covid-19, everyone they could have infected is issued a warning, if they’ve opted in. The system does this matching anonymously on each device, rather than in a central database that governments could use to track the disease more broadly — a feature the companies say is more secure and helps quell user concerns about who sees their sensitive health data.