Many emerging applications are based on group communication model and many group communications Uke multimedia distribution and miUtary applications require a security infrastrocture that provides multiple levels of access control for group members in which group members are divided into a number of subgroups and placed at ditTerent privilege levels based on certain criteria and a member at higher level must be capable of accessing communication in its own level as well as its descendant lower levels and converse is not true.Two key management schemes have been developed to provide hierarchical access control: first method is key-based and the second one is share-based. Constrocting a hierarchical group communication model based on secret shares is more flexible rather than using keys. In this paper we use share-based key management scheme and propose to reduce the storage at higher level users as compared to the scheme proposed by Dexter et al. by reusing a part of the pre-positioned information as common for all the layers in the system. We compare the storage and encryption cost of our scheme with the scheme proposed by Dexter et al. We also address periodic group rekeying.

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