SAS 2006 – IEEE Sensors Applications Symposium Houston, Texas USA, 7-9 February 2006 A Security Framework for Wireless Sensor Networks Tanveer Zia and Albert Zomaya School of Information Technologies University of Sydney Madsen Building F09, Camperdown NSW 2006 Email: {tanzia, zomaya}@it.usyd.edu.au Abstract – Wireless sensor networks are result of developments in micro electro mechanical systems and wireless networks. These networks are made of tiny nodes which are becoming future of many applications where sensor networks are deployed in hostile environments. The deployment nature where sensor networks are prone to physical interaction with environment and resource limitations raises some serious questions to secure these nodes against adversaries. The traditional security measures are not enough to overcome these weaknesses. To address the special security needs of tiny sensor nodes and sensor networks as a whole we introduce a security framework. In our framework we emphasize on three areas: (1) cluster formation (2) secure key management scheme, and (3) a secure routing algorithm. Our security analysis shows that the framework presented in this paper meets the unique security needs of sensor networks. Keywords – Wireless sensor networks security, secure key management, secure routing. I. INTRODUCTION Advancements in micro electro mechanical systems (MEMS) and wireless networks have made possible the advent of tiny sensor nodes called “smart dust” which are low cost small tiny devices with limited coverage, low power, smaller memory sizes and low bandwidth. Wireless sensor networks are consisting of large number of sensor nodes which are becoming viable solution to many challenging domestic, commercial and military applications. Sensor networks collect and disseminate data from the fields where ordinary networks are unreachable for various environmental and strategically reasons. In addition to common network threats, sensor networks are more vulnerable to security breaches because they are physically accessible by possible adversaries, consider sensitive sensor network applications in military and hospitals compromised by adversaries. Many developments have been made in introducing countermeasures to potential threats in sensor networks; however, sensor network security remains less addressed area. In this paper we present a security framework for wireless sensor networks to provide desired security countermeasures against possible attacks. Our security framework consists of three interacting phases: cluster formation, secure key management and secure routing schemes. We make three contributions in this paper: • We discuss cluster formation and leader election in a multihop hierarchical cluster model • We present a secure key management scheme • We propose a secure routing mechanism which addresses potential threats in node to cluster leader and cluster leader to base station and vice versa communication. The rest of paper is organized as follows. Section II provides summary of related work in key management and routing protocols in wireless sensor networks. Section III presents our security framework discussing the cluster formation and leader election process, secure key management scheme, secure routing and their algorithms. Section IV provides analysis of our security framework, and finally in Section V we conclude our paper providing the future research directions. II. RELATED WORK Researchers have addressed many areas in sensor network security. Some of the related work has been summarized in the following paragraphs. Eschenauer et al. [1], present a probabilistic key pre- distribution scheme where each sensor node receives a random subset of keys from a large key pool before deployment. To agree on a key for communication, two nodes find one common key within their subsets and use that key as their shared key. Chan et al [2], extended idea of Eschenauer et al. [14] and developed three key pre-distribution schemes; q-composite, multipath reinforcement, and random-pairwise keys schemes. Pietro et al [3], Present a random key assignment probabilistic model and two protocols; ‘direct and cooperative’ to establish a pairwise communication between sensors by assigning a small set of random keys to each sensor. This idea later converges to pseudo random generation of keys which is energy efficient as compare to previous key management schemes. Liu et al [4] propose a pairwise key schemes is based on polynomial pool-based and grid based key pre-distribution