Using net phone, for example, OpenPhone (C++) and the one in SIPFoundry (JAVA & C++) , to communicate is common nowaday.
In order to let the receiver confirm the identity of the client, we want to deploy the Public key infrastructure (PKI) module over the VoIP system.
All the module are already exist in the Web.
We will provide to you.
For further informatiom, please send e-mail to us.