How will the COVID-19 tracing app work?

The details of the Australian COVID-19 tracing app are not yet available. However, the following description gathered from a number of internet postings is the most likely way it will work.

1. First up you must install the COVID-19 tracing app on your phone. The app will ensure Bluetooth is on permanently.
2. The app on your phone will use Bluetooth to see what other Bluetooth devices are nearby.
3. It will use the Bluetooth signal strength of the other devices to estimate how far away they are.
4. If another Bluetooth device has been within about 1.5 metres for 15 minutes, and the other phone also has the COVID-19 app installed, then the two apps will exchange their phone numbers and save them securely on each phone.
5. This process occurs silently without either phone owner knowing it’s happening, and neither phone owner can see the phone numbers of other phones.
6. If you test positive to COVID-19, those people you’ve been in close contact with will be contacted by health professionals.
7. My guess is that those people will be offered immediate testing for COVID-19.

And that’s it. As apps go it’s about as simple as it gets. And of course the app does not need to know your location at any time.