Nowadays, there have been major advances in the development of low power micro-sensor nodes (sensors for short). The emergence of such sensors has led practitioners to envision networking a large set of sensors scattered over a wide area of interest into a wireless sensor network (WSN) for large-scale event monitoring and data collection and filtering The energy-constrained nature of WSN, the absence of the static infrastructure, the use of wireless channels, and the large number of nodes make the task of incorporating security in WSN a challenging problem. Most of the well known security schemes designed for traditional wire-line and wireless networks introduce significant computation and communication overhead and, thus, cannot be readily applied to WSN. In this paper, we present a novel solution to the problem of key management in WSN. Specifically, we propose a lightweight scheme for clustered WSN based on a combinatorial formulation of the group key management problem. Our solution minimizes the energy and memory consumption of the security protocol. We also introduce a novel key assignment scheme for reducing the potential of collusion by factoring the geographic location of nodes in key assignment.
