Attaching an IMS Subscriber to an Unknown Foreign Network

The networking landscape is about to change. The multitude of different kind of operators and access networks can provide access at any time irrespective of location. However, it will be less likely that every player has pre-established relationships with all the parties. Thus, there is a need for measures that allow the users to securely connect to previously unknown networks and still have the assurance of the home network for the service provisioning. In this paper we describe an architecture, which aims to secure the initial connectivity and the interaction between the involved parties by employing cryptographic identities in a roaming scenario, where the access and home operator have no pre-established agreement. It also allows the operators to take advantage of their existing multimedia service provisioning infrastructures, such as IMS.