As announced in late summer, the developers of the crypto messenger Threema have published the code of the Threema apps as open source. In addition to detailed documentation of the cryptographic process (white paper PDF) and regular security audits, the open sourcing service is intended to guarantee full transparency. As a result, it is no longer necessary to believe the developers’ statements or to trust the assessment of third parties.

The code is subject to the AGPLv3 license, and thanks to so-called reproducible builds, however, can be for the time being only under Android, verify that this corresponds to what the user has installed via Google Play Store or on the device. Thus, for example, manipulated apps can be recognized.

The Threema developers provide the source code via GitHub. The repositories for Threema for Android and Threema for iOS can be found here.

Threema currently costs 1, 49 Euro in the Google Play Store and 1, 99 Euros in the iOS App Store.