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ABSTRACT: We consider the following problem: how can two devices that do not share any secrets establish a shared secret key over a wireless radio channel in the presence of a communication jammer? An inherent challenge in solving this problem is that known anti-jamming techniques (e.g., frequency hopping or direct-sequence spread spectrum) which should support device communication during the key establishment require that the devices share a secret spreading key (or code) prior to the start of their communication. This requirement creates a circular dependency between antijamming spread-spectrum communication and key establishment, which has so far not been addressed. In this work, we propose an uncoordinated frequency hopping (UFH) scheme that breaks this dependency and enables key establishment in the presence of a communication jammer. We perform a detailed analysis of our UFH scheme and show its feasibility, both in terms of execution time and resource requirements.
Security and Privacy, 2008. SP 2008. IEEE Symposium on; 06/2008
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ABSTRACT: In this work, we propose and analyze a new approach for securing localization and location verification in wireless networks based on hidden and mobile base stations. Our approach enables secure localization with a broad spectrum of localization techniques, ultrasonic or radio, based on the received signal strength or signal time of flight. Through several examples, we show how this approach can be used to secure node-centric and infrastructure-centric localization schemes. We further show how this approach can be applied to secure localization in mobile ad hoc and sensor networks.
IEEE Transactions on Mobile Computing 05/2008; · 2.28 Impact Factor
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ABSTRACT: In each country today, cellular networks operate on carefully separated frequency bands. This separation is imposed by the regulators of the given country to avoid interference between these networks. But, the separation is only valid within the borders of a country, hence the operators are left on their own to resolve cross-border interference of their cellular networks. In this paper, we focus on the scenario of two operators, each located on one side of the border. We assume that they want to fine-tune the emitting power of the pilot signals (i.e., beacon signals) of their base stations. This operation is crucial, because the pilot signal power determines the number of users they can attract and hence the revenue they can obtain. In the case of no power costs, we show that there exists a motivation for the operators to be strategic, meaning to fine-tune the pilot signal powers of their base stations. In addition, we study Nash equilibrium conditions in an empirical model and investigate the efficiency of the Nash equilibria for different user densities. Finally, we modify our game model to take power costs into account. The game with power costs corresponds to the well-known prisoner's dilemma: The players are still motivated to adjust their pilot powers, but their strategic behavior leads to a sub-optimal Nash equilibrium.
INFOCOM 2007. 26th IEEE International Conference on Computer Communications. IEEE; 06/2007
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ABSTRACT: Channel allocation was extensively studied in the framework of cellular networks. But the emergence of new system concepts, such as cognitive radio systems, has brought this topic into the focus of research again. In this paper, we study in detail the problem of competitive multi-radio multi-channel allocation in wireless networks. We study the existence of Nash equilibria in a static game and we conclude that, in spite of the non-cooperative behavior of such devices, their channel allocation results in a load-balancing solution. In addition, we consider the fairness properties of the resulting channel allocations and their resistance to the possible coalitions of a subset of players. Finally, we present three algorithms that achieve a load-balancing Nash equilibrium channel allocation; each of them using a different set of available information.
INFOCOM 2007. 26th IEEE International Conference on Computer Communications. IEEE; 06/2007
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ABSTRACT: Due to their very nature, wireless sensor networks are probably the category of wireless networks most vulnerable to "radio channel jamming"-based denial-of-service (DoS) attacks. An adversary can easily mask the events that the sensor network should detect by stealthily jamming an appropriate subset of the nodes; in this way, he prevents them from reporting what they are sensing to the network operator. Therefore, even if an event is sensed by one or several nodes (and the sensor network is otherwise fully connected), the network operator cannot be informed on time. We show how the sensor nodes can exploit channel diversity in order to create wormholes that lead out of the jammed region, through which an alarm can be transmitted to the network operator. We propose three solutions. The first is based on wired pairs of sensors, the second relies on frequency hopping, and the third is based on a novel concept called uncoordinated channel hopping. We develop appropriate mathematical models to study the proposed solutions
IEEE Transactions on Mobile Computing 02/2007; 6(1):100-114. · 2.28 Impact Factor
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ABSTRACT: Channel allocation has been extensively studied in the framework of cellular networks, but the emergence of new system concepts, such as cognitive radio systems, bring this topic into the focus of research again. In this paper, we provide a formal analysis of the selfish multi-radio channel allocation problem using game theory. We conclude that in spite of the non-cooperative behavior of such devices, their channel allocation results in a Pareto- and system-optimal solution. Furthermore, we present a simple algorithm to achieve this efficient channel allocation. To the best of our knowledge, our paper is the first contribution to this important topic.
Distributed Computing Systems Workshops, 2006. ICDCS Workshops 2006. 26th IEEE International Conference on; 08/2006
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ABSTRACT: Inspired by unidirectional error detecting codes that are used in situations where only one kind of bit errors are possible (e.g., it is possible to change a bit "0" into a bit "1", but not the contrary), we propose integrity codes (I-codes) for a radio communication channel, which enable integrity protection of messages exchanged between entities that do not hold any mutual authentication material (i.e. public keys or shared secret keys). The construction of I-codes enables a sender to encode any message such that if its integrity is violated in transmission over a radio channel, the receiver is able to detect it. In order to achieve this, we rely on the physical properties of the radio channel. We analyze in detail the use of I-codes on a radio communication channel and we present their implementation on a Mica2 wireless sensor platform as a "proof of concept". We finally introduce a novel concept called "authentication through presence" that can be used for several applications, including for key establishment and for broadcast authentication over an insecure radio channel. We perform a detailed analysis of the security of our coding scheme and we show that it is secure with respect to a realistic attacker model
Security and Privacy, 2006 IEEE Symposium on; 06/2006
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ABSTRACT: We present a set of simple techniques for key establishment over a radio link in peer-to-peer networks. Our approach is based on the Diffie-Hellmankey agreement protocol, which is known to be vulnerable to the "man-in-the-middle" attack if the two users involved in the protocol do not share any authenticated information about each other (e.g., public keys, certificates, passwords,shared keys, etc.) prior to the protocol execution. In this paper, we solve the problem by leveraging on the natural ability of users to authenticate each other by visual and verbal contact. We propose three techniques. The first is based on visual comparison of short strings, the second on distance bounding, and the third on integrity codes; in each case, the users do not need to enter any password or other data, nor do they need physical or infrared connectivity between their devices. We base our analysis on a well-established methodology that leads us to a rigorous modularization and a thorough robustness proof of our proposal.
Proceedings of the IEEE 03/2006; · 6.81 Impact Factor
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ABSTRACT: CSMA/CA protocols rely on the random deferment of packet transmissions. Like most other protocols, CSMA/CA was designed with the assumption that the nodes would play by the rules. This can be dangerous, since the nodes themselves control their random deferment. Indeed, with the higher programmability of the network adapters, the temptation to tamper with the software or firmware is likely to grow; by doing so, a user could obtain a much larger share of the available bandwidth at the expense of other users. We use a game-theoretic approach to investigate the problem of the selfish behavior of nodes in CSMA/CA networks, specifically geared towards the most widely accepted protocol in this class of protocols, IEEE 802.11. We characterize two families of Nash equilibria in a single stage game, one of which always results in a network collapse. We argue that this result provides an incentive for cheaters to cooperate with each other. Explicit cooperation among nodes is clearly impractical. By applying the model of dynamic games borrowed from game theory, we derive the conditions for the stable and optimal functioning of a population of cheaters. We use this insight to develop a simple, localized and distributed protocol that successfully guides multiple selfish nodes to a Pareto-optimal Nash equilibrium.
INFOCOM 2005. 24th Annual Joint Conference of the IEEE Computer and Communications Societies. Proceedings IEEE; 04/2005
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