Protocols for Secure Communication in Wireless Sensor Networks

Chapter 3
A Security Model for Wireless Sensor
Networks
Wireless sensor networks inherit security vulnerabilities from three classes of
computer systems: (1) As classical computers, they are vulnerable to malicious
code such as viruses. (2) Since they use wireless communications, their
communication links are susceptible to eavesdropping, jamming, or message
injection attacks; they share this characteristic with mobile computers. (3) Sensor
networks often operate in unsupervised, open environments, where they can
be physically accessed by potential adversaries; in this regard, they resemble
embedded systems.
In order to counter the threats stemming from these vulnerabilities, wellknown
mechanisms can be employed, including code authentication, message
encryption and authentication, and tamper proofing (cf. [3]). However, the
specific constraints of sensor networks may be prohibitive to lifting them to a
security level as high as traditional computer systems. Instead, we must explore
solutions that exploit inherent characteristics of sensor networks, such as the
large number of nodes, redundant deployment, and sensoric input, to provide
adequate security guarantees.
In this chapter, we lay the foundations for such approaches by analyzing the
vulnerabilities of WSNs. We concentrate on a type of attack on wireless sensor
networks, which is both specific to and relevant in this domain. The security
mechanisms presented in following chapters will be especially effective with
regard to this threat model. This model assumes an adversary who is able, at a
certain cost, to capture and take control of individual sensor nodes. This enables
the adversary to exploit the capabilities of the captured nodes and participate
in the operation of the sensor network. Depending on the objectives of the
adversary, this may lead to data corruption, denial of service, or data disclosure,
if no countermeasures are utilized.
The strength of an attack is not only determined by the number of cap-