Amiya Bhattacharya

On using reputations in ad hoc networks to counter malicious nodes

Nodes in mobile ad hoc networks have a limited transmission range. Hence the nodes expect their neighbors to relay packets meant for far off destinations. These networks are based on the fundamental assumption that if a node promises to relay a packet, it relays it and does not cheat. This assumption becomes invalid when the nodes in the network have tangential or contradictory goals. The reputations of the nodes, based on their past history of relaying packets, can be used by their neighbors to ensure that the packet is relayed by the node. This paper introduces a reputation scheme for ad hoc networks. Instead of choosing the shortest path to the destination, the source node chooses a path whose next hop node has the highest reputation. This policy, when used recursively, in the presence of 40% malicious nodes, improves the throughput of the system to 65%, from 22 % throughput provided by AODV. This improvement is obtained at the cost of a higher number of route discoveries with a minimal increase in the average hop length according S. Bansal and M. Baker (2003).

Location-Aware Computing, Virtual Networks

This issue includes four works in process on issues and applications in location-aware computing: letting users set and control privacy policies when they use location-aware applications, cold-starting recommender systems for mobile location-aware services, aggregating contextual information for location-based applications, and applying location-based services to public transportation environments. The department also includes a report on lightweight virtualization of low-power wireless personal area networks.

Determining the integrity of application binaries on unsecure legacy machines using software based remote attestation

Integrity of computing platforms is paramount. A platform is as secure as the applications executing on it. All applications are created with some inherent vulnerability or loophole. Attackers can analyze the presence of flaws in a particular binary and exploit them. Traditional virus scanners are also binaries which can be attacked by malware. This paper implements a method known as Remote Attestation entirely in software to attest the integrity of a process using a trusted external server. The trusted external server issues a challenge to the client machine which responds to the challenge. The response determines the integrity of the application.

Obfuscating temporal context of sensor data by coalescing at source

Contextual privacy threat arises from divulging the location and time of the triggering events to adversaries. Since, the context of the triggering events serve as useful information to the eavesdropper, data encryption alone renders inadequate for protecting total privacy of a sensing task. Obfuscation of the contextual information is a natural solution to the contextual privacy problem. Since both location and time of a sensed event constitute its context, obfuscation can be performed both spatially and temporally. In [1], the authors employ spatial obfuscation techniques (controlled flooding, probabilistic flooding and fake messaging) by focusing mainly on the location component of the contextual information. Nevertheless, increased message transmissions place an additional burden on the power constrained sensor nodes.

Mitigating routing vulnerabilities in ad hoc networks using reputations

Nodes in mobile ad hoc networks have limited transmission ranges that necessitate multihop communication. Hence the nodes expect their neighbours to relay the packets meant for nodes out of the transmission range of the source. Ad hoc networks are based on the fundamental assumption that if a node promises to relay a packet, it will relay the packet and will not cheat. This assumption becomes invalid when the nodes in the network have contradictory goals. As a result, routing protocols for ad hoc networks become vulnerable to rogue nodes. The reputations of the intermediate nodes, based on their past history of relaying packets, can be used by their neighbours to ensure that the packet will be relayed by the intermediate nodes. This paper introduces a reputation scheme for ad hoc networks that can motivate the intermediate nodes to relay packets. The source performs a route discovery (using Ad hoc on Demand Distance Vector Routing Protocol (AODV)) and finds a set of routes to the destination. Instead of choosing the shortest route to the destination, the source node chooses a path whose next hop node has the highest reputation. This policy, when used recursively, in the presence of 40% rogue nodes, improves the throughput of the system to 65%, from the 22% throughput provided by AODV with same number of rogue nodes. This improvement is obtained at the cost of a higher number of route discoveries with a minimal increase in the average hop length.

Virtual sensor WPAN on demand

Virtualization of wireless sensor PANs would be useful for general purpose networked sensing with application concurrency, for community-based sensor sharing, and for supporting platform heterogeneity as well as robustness. This abstract presents a snapshot of the preliminary design and implementation of a middleware for lightweight sensor network virtualization that makes use of the latest developments in TinyOS.

SDDA: Sparse and dynamic in-network data aggregation in sensor nets

In-network data aggregation is an effective method to reduce the amount of data transmitted and therefore saves energy consumption in sensor networks. However, data aggregation removes the integrity of original data and thus increases the damage of data falsification attack. This paper proposes four new methods that select a subset of nodes as aggregators in a sparse and dynamic fashion to frustrate the adversary. The criteria for selecting aggregators include security risk, aggregation efficiency gain, and trust relationship among nodes. Simulation results are presented that demonstrate the new methods can effectively make tradeoffs between security risk and communications cost.