Group key management
(GKM) in mobile communication is important to enable access control for a group
of users. A major issue in GKM is how to minimize the communication cost for
group rekeying. To design the optimal GKM, researchers have assumed that all
group members have the same leaving probabilities and that the tree is balanced
and complete to simplify analysis. In the real mobile computing environment,
however, these assumptions are impractical and may lead to a large gap between
the impractical analysis and the measurement in real-life situations, thus
allowing for GKM schemes to incorporate only a specific number of users. In
this paper, we propose a new GKM framework supporting more general cases that
do not require these assumptions. Our framework consists of two algorithms: one
for initial construction of a basic key-tree and another for optimizing the
key-tree after membership changes. The first algorithm enables the framework to
generate an optimal key-tree that reflects the characteristics of users’
leaving probabilities, and the second algorithm allows continual maintenance of
communication with less overhead in group rekeying. Through simulations, we
show that our GKM framework outperforms the previous one which is known to be
the best balanced and complete structure.
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