Eecient Communication-storage Tradeoos for Multicast Encryption

We consider re-keying protocols for secure multicasting in a dynamic multicast group with a center. There is a variety of diierent scenarios using multicast, presenting a wide range of eeciency requirements with respect to several parameters. We give an upper bound on the tradeoo 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 signiicant loss in other parameters. Correctly selecting the parameters of our scheme we can eeciently 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 tradeoo between communication and user storage, and show that our scheme is almost optimal with respect to these lower bounds.