Efficient Communication-Storage Tradeoffs for Multicast Encryption

We consider re-keying protocols for secure multicasting in a dynamic multicast group with a center. There is a variety of different scenarios using multicast, presenting a wide range of efficiency requirements with respect to several parameters. We give an upper bound on the tradeoff between storage and communication parameters. In particular, we suggest an improvement of the schemes by Wallner et al. and Wong et al. [13,14] with sub-linear center storage, without a significant loss in other parameters. Correctly selecting the parameters of our scheme we can efficiently accommodate a wide range of scenarios. This is demonstrated by Applying the protocol to some known benchmark scenarios. We also show lower bounds on the tradeoff between communication and user storage, and show that our scheme is almost optimal with respect to these lower bounds.