howto-srtp

KphoneSI (kpsi) is a SIP (Session Initiation Protocol) user agent for Linux, with which you can in

KPhone SRTP 

Brief:
=====
      This extension provides voice encryption based on the SRTP protocol. 
      
Installation:
============
     see kphoneSI's INSTALL file
     
Configuration:
=============
      Most of the configuration can be set via the GUI 
      (Preferences->SIP Preferences->SRTP).
      - select the Pre-Shared Key (PSK) toggle button
      - enter your SRTP Master key (the master key is a 30 char text.
        Your partner must use the same key!
      - Press OK

Security features:
=================
      The RTP Data is encrypted with a AES counter mode 128 bit cipher.