iCall's Open ZRTP is a cryptographic key-agreement protocol to negotiate the keys for encryption between two end points in a Voice over Internet Protocol (VoIP) phone telephony call based on the Real-time Transport Protocol. It uses Diffie-Hellman key exchange and the Secure Real-time Transport Protocol (SRTP) for encryption.

iCall's Open ZRTP is a cross platform project written in C++. Our testing has shown that it compiles quickly and easily on Win32/64, Mac OS X and many Linux distros.

As of this writing, iCall's Open ZRTP is the only open source zrtp implementation that is released under a LGPL license.

If you intend to implement Open ZRTP in your project, please let us know and please submit any bugs or improvements that you might make.

You can learn more about the Open ZRTP project at http://www.icall.com/developers/open-zrtp