Lower bounds and new constructions on secure group communication schemes

This paper presents both the theoretical and practical aspects of secure group communication schemes. We pointed out that multiple revocation is a fundamentally time-consuming task in secure group communication, by establishing lower bounds for broadcast encryption and group key distribution schemes. We showed that they are O(n) for BE and O(n/m) for GKD respectively, where m is storage requirement and n is the number of users. Thus, they are clearly far more costly than the ideal log bound. In practice, we designed a new broadcast encryption scheme RBE that actually achieves these lower bounds. RBE is shown to outperform most efficient BE schemes in mass revocation. We discuss the influence of join as well as the feasibility of adding it in BE schemes by means of performing full updating or overprovisioning.