TETRA is a European standard for trunked radio used globally by police, military and civilian parties alike. In the past, we already published the hitherto secret inner workings of TETRA and on several of its severe security issues.

We're now back to discuss the last crucial part of TETRA security - its optional (and costly) end-to-end encryption, reserved for the most sensitive use cases. We'll discuss in detail how we obtained and analyzed those elusive algorithms, and what we found.