The Corona Warning App (CWA), which was or is being developed by SAP and Deutsche Telekom on behalf of the Federal Government, is known to need Google Play Services on Android in order to function. This means that an estimated several million people in Germany cannot install the CWA because their smartphone does not meet this requirement.

This is But not only about people for whom their privacy is particularly important and who have therefore removed all Google services from Android, but also, for example, all customers of the Chinese manufacturer Huawei who do not use Google’s services due to legal requirements of the US government may. In order to solve this problem, a group of developers around the app developer cosee GmbH from Darmstadt is developing the open source app CoraLibre – a fork of the official CWA that is supposed to run on Android phones without Google.

No contact tracing without Play Services Shortly after the presentation of the Contact Tracing API developed together with Apple, Google promised to take care of it that it will eventually get by without Play Services, but that doesn’t seem to have a high priority. The group does not even respond to corresponding inquiries on this topic. So it seems to be up to the open source developers to ensure that more people can use the Android version of the CWA. And that’s no small task. In an interview with heise online , the cosee developers explained to us exactly how the Corona warning app works without Google.

Google has therefore integrated its implementation of the Contact Tracing API into the Play Services in order to be able to update this component of the operating system outside of the normal operating system updates. As it is well known, a significant proportion of all Android devices receive updates very late or not at all, so this makes sense for now. However, this means for the CoraLibre developers that they have to implement the Google / Apple API from scratch. And that’s not all. Because Play Services are also responsible for background activities for Android apps, they also had to develop their own mechanism to keep their app active in the background. This was a problem with very early contact tracing apps, such as those from TraceTogether from Singapore, which had to run in the foreground in order to work and were therefore considered to be quite ineffective in real-life situations. The cosee developers solve this with a notification in the status bar of Android, which is supposed to keep the background process for exchanging the Bluetooth data alive.

The CoraLibre project consists of two separate parts: An SDK, which represents the implementation of the Contact Tracing API, and the actual application. The application is a fork of the CWA, which modifies the code from the upstream project by SAP and Telekom so that it works with the CoraLibre SDK. The CoraLibre developers had first tried to bring their code directly upstream in the CWA project, but submitted topics were put on the back burner because the CWA developers were under time pressure. Accordingly, they now operate their own fork, whose code they want to change as little as possible. According to their own statements, they communicate corresponding modifications back to the upstream developers as early as possible. The aim of the CoraLibre project is to have an app in the end that works as exactly as possible like the official app of the federal government, only on Android devices without Play Services.

Millions of Germans are left out The app could potentially involve millions more citizens in contact tracing. Since politicians and experts repeatedly emphasize how important it is – especially now with the daily rapidly increasing positive SARS-CoV-2 tests in the population and the associated overload of the health authorities – that as many citizens as possible use mobile contact tracing to participate, that seems to be a worthwhile goal. Above all, segments of the population could be reached that have not been involved in digital contact tracing to a large extent.

So far, CoraLibre is still not ready for everyday use and is only available as a test version that has to be installed manually and should only be used on test devices. However, the developers hope to be able to publish a version of the app in Google’s Play Store in the next few weeks. The project is partially funded by public funds, including from the Hessian state government. However, the cosee employees are also very happy to receive support from other open source developers. Interested parties who have experience with Android development can participate in the development of the app on GitHub.

(fab)