Dissertation Defense Announcement

Cross-Layer Techniques for Boosting Base-Station Anonymity in Wireless Sensor Networks

Sami Alsemairi

9:30 Wednesday, 9 November 2016, ITE 346

Wireless Sensor Networks (WSNs) provide an effective solution for surveillance and data gathering applications in hostile environments where human presence is infeasible, risky or very costly. Examples of these applications include military reconnaissance, guarding boarders against human trafficking, security surveillance, etc. A WSN is typically composed of a large number of sensor nodes that probe their surrounding and transmit measurements over multi-hop paths to an in-situ Base-Station (BS). The BS not only acts as a sink of all collected sensor data but also provides network management and serves as a gateway to remote commend centers. Such an important role makes the BS a target of adversary attacks that opt to achieve Denial-of-Service (DoS) and nullify the WSN utility to the application. Even if the WSN applies conventional security mechanisms such as authentication and data encryption, the adversary may apply traffic analysis techniques to locate the BS and target it with attacks. This motivates a significant need for boosting BS anonymity to conceal its location.

In this dissertation, we address the challenges of BS anonymity and develop a library of techniques to counter the threat of traffic analysis. The focus of our work is on the link and network layers. We first exploit packet combining as a means to vary the traffic density throughout the network. We call this technique combining the data payload of multiple packets (CoDa), where a node groups the payload of multiple incoming data packets into a single packet that is forwarded toward the BS. CoDa cuts on the number of transmissions that constitute evidences for implicating the BS as a destination of all traffic and thus degrades the adversary’s ability in conducting effective traffic analysis.

Next we develop a novel technique for increasing BS anonymity by establishing a sleep/active schedule among the nodes that are far away from the BS, and increasing the traffic density in selected parts of the network in order to give the impression that the BS is located in the vicinity of the sleeping nodes. We call this technique Adaptive Sampling Rate for increased Anonymity (ASRA). Moreover, we develop three novel techniques based on a hierarchical routing topology. The first, which we call Hierarchical Anonymity-aware Routing Topology (HART), forms clusters and an inter-cluster-head routing topology so that a high traffic volume can be observed in areas away from the BS. The second is a novel cross-layer technique that forms a mesh topology. We call this technique cluster mesh topology to boost BS’s anonymity (CMBA). CMBA opts to establish a routing topology such that the traffic pattern does not implicate any particular node as a sink.

The third technique creates multiple mesh-based routing topologies among the cluster-heads (CHs). By applying the closed space-filling curves such as the Moore curve, for forming a mesh, the CHs are offered a number of choices for disseminating aggregated data to the BS through inter-CH paths. Then, the BS forwards the aggregated data as well so that it appears as one of the CH. We call this technique boosting the BS anonymity through multiple mesh-based routing topologies (BAMT). We validate the effectiveness of all anonymity-boosting techniques through simulation and highlight the trade-off between anonymity and overhead.