Establishing Pairwise Keys in Heterogeneous Two-Tiered Wireless Sensor Networks

Key management is an important cryptographic primitive upon which other security services are built. Most of the existent pairwise key management protocols consider homogenous ad hoc sensor networks. However, recent researches have demonstrated the limitation of this architecture in terms of performance and scalability. Therefore, this paper focuses on proposing a pairwise key management protocol for heterogeneous multi-tiered wireless sensor network that leverages the existence of a small percentage of more capable sensor nodes. The heterogeneity among sensor nodes helps provide scalability, notable energy efficiency and security benefits. The proposed protocol uses both probabilistic key pre-distribution in the lower tier of the network architecture and public key cryptography in the upper tier to distribute session keys. The performance of our solution is evaluated analytically with respect to communication, computation, and memory overhead. We demonstrate that the proposed key establishment protocol provides a high level of security while at the same time minimizes the resource consumption of the sensor devices. These results are highlighted when comparing our proposed protocol with three well known key establishment protocols implemented for WSN.