A comment by Julian Kunkel, Simon Worthington, Jeremy Bennett, Andy Bennett

Governments worldwide are developing smartphone apps that track the location and movement profile of citizens in order to quickly identify contact persons of COVID-19 infections. According to The Financial Times, if even 40% of smartphone users install such an application, the infection levels would be significantly reduced in the UK. Therefore, the widespread usage of such an application is an important instrument in the current crisis.

How could such a smartphone app work? In a nutshell, a device can scan other nearby devices and exchange device IDs, for example, using Bluetooth. This information then needs to be stored with a timestamp. If the owner of a device contracts the virus, s/he could indicate this fact in the app allowing to associate the own device ID with the information that s/he may have infected others. This data then needs to be recorded on a server to allow the app of other users to query the register and then compare any contact information with the register of COVID-19 victims.