GNU ZRTP is a C++ implementation of Phil Zimmermann's ZRTP
specification and is available under the GPL license.

The complete GNU ZRTP implementation consists of two main parts,
the GNU ZRTP core (independent from the OS and the RTP/SRTP
implementation) and an RTP/SRTP implementation specific glue code.
The current GNU ZRTP distribution contains glue code to bind GNU ZRTP
to GNU ccRTP.