Apple and Google developed the Google-Apple Exposure Notification system in order to provide a uniform API for contact-tracing apps while preserving user privacy. On Android, GAEN is integrated in the Google Play services, which is proprietary. As a consequence, users wanting to keep a free system, as well as phone manufacturers such as Huawei who don't have Google Play services cannot use these applications. This project aims to offer an alternative framework, based on open-source code, which requires only minimal changes to the apps.