Nicole Schmidt

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Programmed in less than 50 Days: Deutsche Telekom and SAP publish Corona Warn app

  • More than 6 million downloads already
  • The largest open-source project by the German government 
  • The "ideal app" for Germany
Corona warning app

Germany’s IT industry delivers: After just 50 days, the German government’s Corona Warn app was ready to go and has been available to download from both the Apple App Store and the Google Play Store since the evening of June 15. The app has already been downloaded over six million times since then. The app was created in close collaboration between SAP and Deutsche Telekom, along with other partners. The two companies developed the app under an open-source approach. The development of the program coding could be followed continuously on the GitHub developer platform. Experts could monitor the development status at all times. As a result, every line of code is transparent for the general public. Over the course of the app development, more than 109,000 individual visitors viewed the coding and there were some 7,250 contributions from community and project team members. It’s hard to imagine how a software project of such crucial importance could have been developed more transparently. The Corona Warn app is the largest open-source project ever carried out on behalf of the German government.

With this app, Deutsche Telekom, with the new “Digital Solutions” division of T-Systems, and SAP have digitalized a process for the successful interruption of infection chains with regard to the COVID-19 pandemic: from possible infection to the warning of potentially exposed contact persons and from smartphone to testing lab. The user experience – operation, data privacy, and hotline integration – was always the focus of development. The Corona Warn app, which was ordered by the German government, is one of the first European apps to be based on the current specifications of the Exposure Notification Framework provided by Apple and Google. This enables users of Android-based smartphones and iPhones to run the app on their devices in the background, while continuing to use their favorite apps at the same time.  



Aspects of data privacy and data security, in particular, were covered in close collaboration with key public institutions like the German Federal Office for Information Security (BSI) and Germany’s Federal Data Protection Commissioner (BfDI). The app does not require users to enter any personal data at all. The Corona Warn app does not need information like name, age, or address, nor does it track user locations. The app only shares randomly generated keys when two smartphones get in close proximity of each other for a certain period of time. The keys from the recorded encounters are saved directly on the users’ smartphones. It is not possible to determine which device is behind a particular key, because the keys are encrypted. The BSI has determined that the source code has a very high level of quality. The developer team has followed recognized best practices for software architecture, programming style, and software security. All critical vulnerabilities identified by the BSI over the course of the open-source development process were eliminated quickly.

The “ideal app” for Germany

Decentralized, voluntary, and without user identifiability – according to the Nuremberg Institute for Market Decisions, these are the most important characteristics Germans want from a coronavirus tracing app. The Corona Warn app developed by Deutsche Telekom and SAP on behalf of the German government meets all of these demands. The two companies worked together to create a digital solution that takes the general public’s desire for privacy into account in the battle against the COVID-19 pandemic.

Prime example of a collaborative partnership at the highest level

“With the Corona Warn app, we have shown that we can create digital solutions ‘Made in Germany’ as partners, even under challenging conditions – and do it quickly, yet securely for millions of private users,” says Adel al-Saleh, CEO of T-Systems.

"The project team worked closely together to develop an app in record time that will help us interrupt the infection chains of the coronavirus. The engagement on the GitHub open-source platform was outstanding and a clear sign of the lively software engineering culture in Germany,” adds Jürgen Müller, Chief Technology Officer and SAP SE Executive Board member. “The important thing now is to encourage as many people as possible to use the app.”

About Deutsche Telekom: Deutsche Telekom at a glance



Information related to the Covid-19 pandemic and the Corona Warn App in the years 2020 and 2021.