Performance Evaluation of Key Management Schemes in Wireless Sensor Networks

Gazi University Journal of Science GU J Sci 25(2):465-476 (2012) ORIGINAL ARTICLE Performance Evaluation of Key Management Schemes in Wireless Sensor Networks Önder KHALIL1,♠, Suat ÖZDEMİR1 1 Gazi University, Computer Engineering Department, Maltepe Ankara Received: 24.07.2011 Revised: 30.11.2011 Accepted:04.02.2012 Abstract Wireless sensor networks are being deployed in wide variety of applications, including military sensing and tracking, environment monitoring, patient monitoring and tracking, smart environments, etc. When a wireless sensor network is deployed in such hostile environment, security becomes an extremely important issue. Confidentiality, integrity, and availability are typical security goals for wireless sensor networks. Providing these goals to secure communication among sensor nodes typically depends on the use of cryptographic schemes. When employing a cryptographic scheme, a key management service is always required. The objective of this paper is to evaluate the most important key management schemes in wireless sensor networks which are single network-wide key scheme, pairwise key establishment scheme, random key predistribution, and Q-composite random key predistribution scheme. The evaluation is performed in OMNET++ simulation environment and the metrics are selected as secure connectivity achievement, memory overhead, communication overhead, and resilience against node capture attacks. Based on the simulation results, the advantages and disadvantages of each scheme are presented. The simulation results show that there is no general purpose key management scheme that can fit all the security requirements of wireless sensor networks. However, in terms of the performance metrics, the most suitable scheme for wireless sensor networks is the random key predistribution scheme. Key words: key management, security, performance evaluation, analysis, wireless sensor networks. 1. INTRODUCTION A recent technology review indicates that sensor technology is one of the ten emerging technologies that will change the world [1]. Developments in sensor network technology accelerated the deployment of Wireless Sensor Networks (WSNs) which usually consist of a large number of ultra-small autonomous devices. Each device, called sensor node, is battery Corresponding author, e-mail: powered and equipped with integrated sensors, a data processing unit, and a short-range radio communication unit. Sensor nodes are significantly constrained in terms of energy, memory, and computational capacity [2]. Figure 1, adopted from [5] depicts a schematic diagram of a sensor node’s components. Basically, each sensor node is composed of a sensing, processing, transmission and power units (some of these components are optional, such as the mobilizer) [3]. 466 GU J Sci, 25(2):465-476 (2012)/ Önder KHALIL, Suat ÖZDEMİR Figure 1. The components of a typical wireless sensor node [5]. In WSNs, sensor nodes are generally deployed randomly to the field of interest. The deployment environment may be on land, underground, or underwater [4]. Using wireless communication, sensor nodes form a network to collaborate on sensing the physical environment at unprecedented resolution, improving sensing quality and enabling new applications. The sensor nodes collected the data, perform data aggregation and then send the result to the sink (or base station) as can be seen in Figure 2. Figure 2. Sensor nodes scattered in a sensor field. Sensor nodes in WSNs can be used to gather and process data from the environment (e.g., mechanical, thermal, biological, chemical, and optical readings), enabling many applications such as environment and habitat monitoring, support for logistics, health care and emergency response, as well as military operations [6,7]. These networks usually deployed and left in an unattended area for a long time. Due to their unattended nature, WSNs pose security and privacy challenges. In some applications, sensor nodes have to be deployed in hostile environments and hence are subject to various external and internal attacks. For example, an adversary can easily gain access to mission critical information by monitoring wireless communications among sensor nodes, or inject false messages into the networks through some compromised nodes. Therefore, it is crucial to deploy secret keys into WSNs to encrypt wireless communications or establish authentication among sensor nodes. The challenge is how to efficiently generate, distribute and maintain secret keys among sensor nodes. This problem is called key management problem for WSNs and can be solved by carefully designed key management schemes. Traditional key distribution schemes cannot be directly used in WSNs due to their unique properties [8]. When designing a key management scheme for WSNs, designers should take the following five major resource constraints of sensor nodes into consideration: (1) limited energy, (2) limited memory, (3) limited computing power, (4) limited communication bandwidth, (5) limited communication range [8]. In addition to these constraints, there is also lack of physical security of sensor nodes. WSNs are deployed in unattended and hostile regions, and therefore physical security of sensor nodes cannot be guaranteed. The lack of physical security results in node capture attacks where an attacker gains the control of a node in the network after deployment. Once in control of that node, the attacker can maliciously alter the node to listen to information in the network, input false data, and perform various attacks on the network. The attacker may also simply obtain the information critical GU J Sci, 25(2):465-476 (2012)/ Önder KHALIL, Suat ÖZDEMİR to the network’s security such as routing protocols, data, and security keys [10]. Hence, key distribution schemes of WSNs must consider the compromised nodes as well. The objective of key management is to establish and maintain secure and dynamic channels among communicating nodes [9]. The desired features of key management scheme can be summarized as follows: Scalability: Efficiency demands that WSNs utilize a scalable key management scheme to allow for variations in the size of the network. Key management schemes should provide their features for small size networks, but also maintain these characteristics when applied to larger ones. Flexibility: Key establishment techniques should be able to function well in any kind of environments and support dynamic deployment of nodes, i.e., a key establishment technique should be useful in multiple applications and allow for adding nodes at any time. Memory: Memory availability of sensor nodes is usually 6–8 Kbps, half of which is occupied by a typical sensor network operating system. Key establishment techniques must use the remaining limited storage space efficiently by storing keys in memory, buffering stored messages, etc. Key management schemes of WSNs should take into consideration all the aforement (...truncated)