Secure and practical key establishment for distributed sensor networks

Key establishment in sensor networks is a challenging task, due to the physical constraints of sensor devices and their exposure to several threats. Existing protocols based on symmetric cryptography are very efficient but they are weak against several node impersonation and insider attacks. On the other hand, asymmetric protocols are resilient to such attacks but unfortunately, they are not feasible for sensor networks, even in their most efficient versions (e.g. the Elliptic Curve Diffie-Hellman family of key agreement protocols). In this paper we present two pairwise key establishment protocols for sensor nodes in unattended Distributed Sensor Networks (DSNs). The first protocol is hybrid and it combines asymmetric (Elliptic Curve) cryptography with symmetric key techniques. The second protocol is fully asymmetric. Furthermore, through simulations, we measure the efficiency of the proposed protocols in comparison with existing hybrid protocols. Our results show that under conditions, it is feasible for highly sensitive applications of static sensor networks to employ partial or fully asymmetric key establishment techniques and thus extend their security properties.