Security analysis of tree and non-tree based group key management schemes under strong active outsider attack model

Key management schemes for secure group communications should satisfy two basic security requirements, backward secrecy and forward secrecy. Most of the prominent secure group key management schemes are shown to satisfy the basic security requirements considering passive attack model. In this paper, we analyze secure group key management schemes under active outsider attack model. In active outsider attack model, an adversary can compromise a legitimate user of the group. We show that some of the efficient tree based, non-tree based and proxy re-encryption based group key management schemes are not secure under active attack model. We evaluate the cost involved in making these schemes secure under active attack model. Also, we construct a secure version of these schemes and show that the schemes are secure under active outsider attack model.