International Association
for Cryptologic Research

In this paper, we review three problematic key management(KM) schemes recently proposed, including Kayam\'s scheme for groups with hierarchy [9], Piao\'s group KM scheme [13], Purushothama\'s group KM schemes [15]. We point out the problems in each scheme. Kayam\'s scheme is not secure to collusion attack. Piao\'s group KM scheme is not secure and has a bad primitive. The hard problem it bases is not really hard. Purushothama\'s scheme has a redundant design that costs lots of resources and doesn\'t give an advantage to the security evel and dynamic efficiency of it. We also briefly analyze the underlying reasons why these problem emerge.