Germany's Covid contact tracing app is Open Source
I really question whether these apps will be effective. The limitation section <a href="https://github.com/corona-warn-app/cwa-documentation/blob/master/solution_architecture.md#limitations" rel="nofollow">https://github.com/corona-warn-app/cwa-documentation/blob/ma...</a> of their architecture document shows that people in close proximity for a few minutes may not even get picked up.<p>Anyone who has dealt with trying to work out distance from Bluetooth signal strength will know that it is virtually impossible once you factor in, the orientation of two devices (signal polarization), their locations (in a pocket, bag, case...) and the local environment (reflections and attenuation from walls, floors ceilings, furniture).<p>Additionally, without knowing exactly how transmission is occurring the risk score calculation <a href="https://github.com/corona-warn-app/cwa-documentation/blob/master/solution_architecture.md#risk-score-calculation" rel="nofollow">https://github.com/corona-warn-app/cwa-documentation/blob/ma...</a> may be wildly inaccurate too resulting in the wrong people being notified.<p>And even assuming perfect ability to deduce the risk of infection of two people using the app, will that help in the bigger context. If the people most at risk don't install this app and the least at risk do then you may be drawing resources away from the people that most need help.