Scalable multicast security in dynamic groups

In this paper we propose a new framework for multicast security based on distributed computation of security transforms by intermediate nodes. The involvement of intermediate nodes in the security process causes a new type of dependency between group membership and the topology of the multicast network. Thanks to this dependency, the containment of security exposures in large multicast groups is assured. The framework also assures both the scalability for large dynamic groups and the security of individual members. Two different key distribution protocols complying with the framework are introduced. The first protocol is an extension of the El Gamal encryption scheme whereas the second is based on a multi-exponent version of RSA.