Pruned nodes in ternary key tree during batch rekeying in group key agreement for cognitive radio ad hoc networks

Cognitive radio networks need stringent and secure group communication as nodes dynamically access the free portions of radio frequency spectrum to solve the spectrum scarcity in wireless networks. The cognitive radio ad hoc networks can use group key agreement to achieve security in group communication and tree topology to organize the group members in order to reduce the complexity of group operations. This paper proposes a ternary key tree model for tree- based group key agreement in cognitive radio ad hoc networks, and it considers batch rekeying scheme. The range of ids for member, nonmember and pruned nodes in the ternary key tree are analysed in this paper. This paper proposes the analysis of two types of leave operations in the key tree, and the concept of subtree structure is used to analyse the total number of internal nodes that are pruned during leave operations in the key tree through mathematical expressions. This pruned nodes analysis can be used in finding the total number of renewed nodes in the key tree during rekeying process to measure the communication complexity of tree- based group key agreement protocol. Copyright (C) 2015 John Wiley & Sons, Ltd.