+
+ + Install srtp (optional) for call encryption :
+ $ git clone git://git.linphone.org/srtp.git
+ $ cd srtp && autoconf && ./configure && make
+ $ sudo make install
+
+ + Install zrtpcpp (optional), for unbreakable call encryption
+ $ sudo apt-get install cmake libssl-dev
+ $ git clone git://git.linphone.org/zrtpcpp.git
+ $ cd zrtpcpp && cmake -Denable-ccrtp=false . && make
+ $ sudo make install