Temporal Privacy in Wireless Sensor Networks

1. Temporal Privacy in Wireless Sensor Networks Pandurang Kamat, Wenyuan Xu, Wade Trappe, Yanyong Zhang Wireless Information Network Lab Rutgers University

2. Outline • Introduction • Application Scenario • Assumptions • Formulation • Simulation • Challenges

3. Introduction • Sptaio-temporal information in wireless sensor networks are important. • Must ensure that • location of source nodes (Extensively discussed) • time when source nodes observed the target (received little attention) • Temporal privacy is defined as the mutual information between the received time sequences and the creation time sequences.

4. Introduction • In order to minimize the mutual information, buffer each packet at intermediate nodes along the routing path between a source and the sink. • According to information-theoretic study, using random delays that follow an exponential distribution will better protect temporal privacy than other distributions.

5. Application Scenario • Animal habitat • Animals move through the environment with sensor network ready • One sink and monitor the locations of animal

6. Assumptions • The assumptions for the adversay are • Able to eavesdrop (read packet header) • Unable to decrypt the packet • Able to estimate packet creation time based on network knowledge • Unable to interfere with the proper function of the wireless sensor network • Unable to inject or modify packets, alter the routing path, or destroy sensor devices. • Always located in the node of the sink and only observes the packets into the sink.

7. Formulation h τ time z x x’ h: hop count τ: transmission delay x: true creation time x’ : estimated creation time (x’ –x)2 : mean square error Higher estimation error better preserves the temporal privacy of the source.

8. Formulation • Use the concept of differential entropy in Information Theory to generate a formula and show that choosing a delay distribution will make adversary learn as little as possible about x from z.

9. Adaptive Buffering • Packets will buffer in an intermediate node with a random time along the routing path from a source to the sink. • Adaptive buffering strategy that preempts buffered packets to accommodate newly arriving packets if the buffer is full. They call it as RCAD (Rate-Controlled Adaptive Delaying)

10. Simulation

11. Challenges • High cost of a sensor with large enough buffer size • High traffic v.s. very limited buffer size