The appeal of applications for multipoint communication has increased significantly along with the greater availability of conference partners in the internet. In order to manage the transmission of high bandwidth multimedia streams, produced by special tools for video and audio conferencing or shared editing, new multicast protocols are needed for improved scaling and a more efficient usage of network resources.

The use of the multicast capable internet backbone, the MBone for business conferencing, entertainment, education, gaming and private conversation has led to an increased interest in security issues such as authentication and privacy. While a lot of effort is  being made to integrate new mechanisms to provide the most common security services in  IP-multicast protocols, the aspect of anonymity has not yet been taken into consideration.

There are different attempts for dealing with the problem of anonymity on the basis of one-to-one communication in the World Wide Web. General concepts such as Mixes or Crowds have been implemented in successful projects e.g. The Anonymizer, Onion-Routing or Janus/Rewebber. These projects provide anonymity for the client and, in the case of Janus, for the web server as well.

The research carried out at the Department of Communication Systems started by combining the research fields of multicast communication and anonymity in the global internet. The underlying protocols used for sending, routing and receiving multicast messages were intentionally designed for test purposes only and are now used by a much larger community. The idea was to develop mechanisms and protocols for providing receiver and sender anonymity. The main goals of design were: 

• Compatibility with the current multicast framework - the solution should work without changing existing components,
• Minimization of protocol overheads - the advantages of efficient media distribution via multicast should remain,
•  Scalability of the system depending on the degree of desired security measures and the number of hosts participating in specific multicast sessions.
  

A number of models were developed to solve this set of problems. These were the Dedicated and Shared Multicast Anonymizer for receiver anonymity and the Shared Sender Anonymizer for sender anonymity. Further work included the formal analysis of the trial and evaluation of a prototype, which has been implemented using Java.