Farinaz Koushanfar

Coverage problems in wireless ad-hoc sensor networks

Wireless ad-hoc sensor networks have recently emerged as a premier research topic. They have great long-term economic potential, ability to transform our lives, and pose many new system-building challenges. Sensor networks also pose a number of new conceptual and optimization problems. Some, such as location, deployment, and tracking, are fundamental issues, in that many applications rely on them for needed information. We address one of the fundamental problems, namely coverage. Coverage in general, answers the questions about quality of service (surveillance) that can be provided by a particular sensor network. We first define the coverage problem from several points of view including deterministic, statistical, worst and best case, and present examples in each domain. By combining the computational geometry and graph theoretic techniques, specifically the Voronoi diagram and graph search algorithms, we establish the main highlight of the paper-optimal polynomial time worst and average case algorithm for coverage calculation. We also present comprehensive experimental results and discuss future research directions related to coverage in sensor networks.

A Survey of Hardware Trojan Taxonomy and Detection

Editors note:Todays integrated circuits are vulnerable to hardware Trojans, which are malicious alterations to the circuit, either during design or fabrication. This article presents a classification of hardware Trojans and a survey of published techniques for Trojan detection.

Exposure in wireless Ad-Hoc sensor networks

Wireless ad-hoc sensor networks will provide one of the missing connections between the Internet and the physical world. One of the fundamental problems in sensor networks is the calculation of coverage. Exposure is directly related to coverage in that it is a measure of how well an object, moving on an arbitrary path, can be observed by the sensor network over a period of time. In addition to the informal definition, we formally define exposure and study its properties. We have developed an efficient and effective algorithm for exposure calculation in sensor networks, specifically for finding minimal exposure paths. The minimal exposure path provides valuable information about the worst case exposure-based coverage in sensor networks. The algorithm works for any given distribution of sensors, sensor and intensity models, and characteristics of the network. It provides an unbounded level of accuracy as a function of run time and storage. We provide an extensive collection of experimental results and study the scaling behavior of exposure and the proposed algorithm for its calculation.

Worst and best-case coverage in sensor networks

Wireless ad hoc sensor networks have recently emerged as a premier research topic. They have great long-term economic potential, ability to transform our lives, and pose many new system-building challenges. Sensor networks also pose a number of new conceptual and optimization problems. Here, we address one of the fundamental problems, namely, coverage. Sensor coverage, in general, answers the questions about the quality of service (surveillance) that can be provided by a particular sensor network. We briefly discuss the definition of the coverage problem from several points of view and formally define the worst and best-case coverage in a sensor network. By combining computational geometry and graph theoretic techniques, specifically the Voronoi diagram and graph search algorithms, we establish the main highlight of the paper - an optimal polynomial time worst and average case algorithm for coverage calculation for homogeneous isotropic sensors. We also present several experimental results and analyze potential applications, such as using best and worst-case coverage information as heuristics to deploy sensors to improve coverage.

EPIC: ending piracy of integrated circuits

As semiconductor manufacturing requires greater capital investments, the use of contract foundries has grown dramatically, increasing exposure to mask theft and unauthorized excess production. While only recently studied, IC piracy has now become a major challenge for the electronics and defense industries. We propose a novel comprehensive technique to end piracy of integrated circuits (EPIC). It requires that every chip be activated with an external key, which can only be generated by the holder of IP rights, and cannot be duplicated. EPIC is based on (i) automatically-generated chip IDs, (ii) a novel combinational locking algorithm, and (Hi) innovative use of public-key cryptography. Our evaluation suggests that the overhead of EPIC on circuit delay and power is negligible, and the standard flows for verification and test do not require change. In fact, major required components have already been integrated into several chips in production. We also use formal methods to evaluate combinational locking and computational attacks. A comprehensive protocol analysis concludes that EPIC is surprisingly resistant to various piracy attempts.

Physical Unclonable Functions and Applications: A Tutorial

This paper describes the use of physical unclonable functions (PUFs) in low-cost authentication and key generation applications. First, it motivates the use of PUFs versus conventional secure nonvolatile memories and defines the two primary PUF types: “strong PUFs” and “weak PUFs.” It describes strong PUF implementations and their use for low-cost authentication. After this description, the paper covers both attacks and protocols to address errors. Next, the paper covers weak PUF implementations and their use in key generation applications. It covers error-correction schemes such as pattern matching and index-based coding. Finally, this paper reviews several emerging concepts in PUF technologies such as public model PUFs and new PUF implementation technologies.

Lightweight secure PUFs

To ensure security and robustness of the next generation of Physically Unclonable Functions (PUFs), we have developed a new methodology for PUF design. Our approach employs integration of three key principles: (i) inclusion of multiple delay lines for creation of each response bit; (ii) transformations and combination of the challenge bits; and (iii) combination of the outputs from multiple delay lines; to create modular, easy to parameterize, secure and reliable PUF structures. Statistical analysis of the new structure and its comparison with existing PUFs indicates a significantly lower predictability, and higher resilience against circuit faults, reverse engineering and other security attacks.

Fault tolerance techniques for wireless ad hoc sensor networks

Embedded sensor network is a system of nodes, each equipped with a certain amount of sensing, actuating, computation, communication, and storage resources. One of the key prerequisites for effective and efficient embedded sensor systems is development of low cost, low overhead, high resilient fault-tolerance techniques. Cost sensitivity implies that traditional double and triple redundancies are not adequate solutions for embedded sensor systems due to their high cost and high energy-consumption. We address the problem of embedded sensor network-fault-tolerance by proposing heterogeneous back-up scheme, where one type of resource is substituted with another. First we propose a broad spectrum of heterogeneous fault-tolerance techniques for sensor networks including the ones where communication and sensing are mutually backing up each other. Then, we focus our attention on two specific approaches where we back-up one type of sensors with another type of sensor. In the first, we assume faults that manifest through complete malfunctioning and in the second, we assume sensors where fault manifest through high level of error.

On-line fault detection of sensor measurements

On-line fault detection in sensor networks is of paramount importance due to the convergence of a variety of challenging technological, application, conceptual, and safety related factors. We introduce a taxonomy for classification of faults in sensor networks and the first on-line model-based testing technique. The approach is generic in the sense that it can be applied on an arbitrary system of heterogeneous sensors with an arbitrary type of fault model, while it provides a flexible tradeoff between accuracy and latency. The key idea is to formulate on-line testing as a set of instances of a non-linear function minimization and consequently apply nonparametric statistical methods to identify the sensors that have the highest probability to be faulty. The optimization is conducted using the Powell nonlinear function minimization method. The effectiveness of the approach is evaluated in the presence of random noise using a system of light sensors.

Techniques for Design and Implementation of Secure Reconfigurable PUFs

Physically unclonable functions (PUFs) provide a basis for many security and digital rights management protocols. PUF-based security approaches have numerous comparative strengths with respect to traditional cryptography-based techniques, including resilience against physical and side channel attacks and suitability for lightweight protocols. However, classical delay-based PUF structures have a number of drawbacks including susceptibility to guessing, reverse engineering, and emulation attacks, as well as sensitivity to operational and environmental variations. To address these limitations, we have developed a new set of techniques for FPGA-based PUF design and implementation. We demonstrate how reconfigurability can be exploited to eliminate the stated PUF limitations. We also show how FPGA-based PUFs can be used for privacy protection. Furthermore, reconfigurability enables the introduction of new techniques for PUF testing. The effectiveness of all the proposed techniques is validated using extensive implementations, simulations, and statistical analysis.