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.
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