Hello, have you heard of Minisip? It is a free softphone which concentrates on security. It is developed by the Royal Institute of Technology (KTH, Stockholm, Sweden). I have tested to place encrypted calls with the commercial versions of X-Lite (called eyeBeam) and Zoiper (ZoiperBiz). While there were problems with eyeBeam I managed to place encrypted calls (signalling AND media) with ZoiperBiz via FreeSWITCH. Meanwhile there's an update available for eyeBeam which I have not tested. Maybe it works now, too. .
Do I understand this correctly that there aren't any softphone clients that support SRTP via SDES correctly ? I found few clients that support SRTP here <http://en.wikipedia.org/wiki/Comparison_of_VoIP_software> http://en.wikipedia.org/wiki/Comparison_of_VoIP_software but I haven't tested them yet.
-- Alois Komenda Fraunhofer-Einrichtung für Systeme der Kommunikationstechnik ESK