How is ExposureConfiguration set in SwissCovid ?

[pdehaye]

The CoronaRiskScoring project is trying to assess how different contact tracing apps are being parametrized. We are first focusing on apps using the Apple API (see its description on our wiki) as it will enable quickest comparison.

Project considered
We are looking at SwissCovid.

What we need
We need pointers to the places in the code where the following parameters are set:

• ENExposureConfiguration.attenuationLevelValues,
• ENExposureConfiguration.daysSinceLastExposureLevelValues,
• ENExposureConfiguration.durationLevelValues,
• ENExposureConfiguration.transmissionRiskLevelValues and
• ENExposureConfiguration.metadata.attenuationDurationThresholds

Nice to have
We would also like to understand what is done with ENExposureDetectionSummary and ENExposureInfo, after the risks are calculated.

Excellent to have
This is only the beginning for us. We want the above so we can track how the parameters are being changed. It is likely actually that this is passed dynamically to the apps. If so, we need to know the process behind these changes, so we can ask the right people for this information.

If you have pointers in the right direction, they would be greatly appreciated.

[pdehaye]

It turns out SwissCovid doesn't use much of risk scoring part of the Google/Apple API actually, at least in the present configuration!

In a public call ahead of the trial phase, as well as in this document, DP-3T explains they only use the summary parts of the APIs, not the risk calculation parts.

For the same question, but approached from the app side(s), see:

• How are parameters passed around? SwissCovid/swisscovid-app-ios#71 on the iOS app repository attempts to clarify quite a bit of the question.
• (EDIT: ) How are parameters passed around? DP-3T/dp3t-app-android-demo#62 does the same on the Android side.

[pdehaye]

The backend server provides the relevant parameters.

For instance:

https://www.pt.bfs.admin.ch/v1/config?appversion=&osversion=&buildnr=

https://github.com/DP-3T/dp3t-app-android-ch/blob/2d7a09a6934695df985049904e09c28b561cbe6b/app/src/main/java/ch/admin/bag/dp3t/networking/ConfigWorker.java#L90-L92

The appversion value comes from here.

[pdehaye]

It is still not clear to me what are the valid parameters to pass to the API above, on Android and iOS, for the different appversions, and especially each build.

On iOS, this seems related since it constructs the call.