Key management and link-layer security of wireless sensor networks : energy-efficient attack and defense

Abstract

The relentless miniaturization of computers and advances in radio-based communications have given rise to a new exciting technology: wireless sensor networks (WSNs). A WSN is a network consisting of numerous small, low-cost, independent sensor nodes that communicate through wireless means. These sensor nodes are self-contained units composed primarily of a microcontroller, a radio, a battery, one or more sensors and some interconnecting circuits. As such, the sensor nodes have limited computing power and energy supply, and instead of performance, they are frequently operated with energy efficiency in mind. Sensor nodes are meant to be deployed without a pre-configured topology and operated unattended, but radio communications enable them to organize themselves. When data are available through their sensors, radio communications allow the data to be distributed across the network. For monitoring-type applications, e.g. monitoring of natural habitats, this presents unprecedented sensing scale and resolution. For other types of applications, at the same time providing a transparent interface between human activities and the surroundings, WSNs integrate seamlessly with the environment. As with other technologies, WSN is not without its perils. When data are circulated in an unattended network, they might be leaked against the interests of the concerned parties. Operation-wise, there should be some means to ensure the availability of the service provided by the network, as well as a way to discriminate between legal and malicious requests to avoid executing tasks that might be disruptive to the network itself. This is where security comes in. These problems are largely categorized as information security and security against denial-of-service (DoS) attacks, and they are the foci of this thesis. The common thread that permeates through these two areas is energy efficiency. While security can be gained by tamper-proofing the hardware, increasing the computational power of the sensor nodes and so on, practical WSN security is a balancing act that is constantly in search of the highest level of protection that can be squeezed out of the judicious use of limited resources. The thesis is divided into two parts. The first part of the thesis concerns defense-oriented issues: design, implementation and key management. The second part of the thesis looks at attack-oriented issues: link-layer jamming attacks.