  The greatest threat in the new generation network which is called ngn is
unsafe authentication. Communication between new servers in ngn world is done
based on Session Initiation Protocol. SIP is an application layer control
operating on top of a transport protocol which allows creating modifying and
terminating sessions among more agents. For authentication SIP relies on HTTP
Digest by default the client is authenticated to the SIP proxy server called
one way authentication because in this approach we can authenticate client to
server and the client cant do any authentication in server side. In this paper
we propose a mutual authentication mechanism that is not based on HTTP Digest
and then we implement our method in IMS and start to do authentication client
to server is done in first step and server to client next.
