| 1. |
- Poturalski, Marcin, et al.
(författare)
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On Secure and Precise IR-UWB Ranging
- 2012
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 11:3, s. 1087-1099
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Tidskriftsartikel (refereegranskat)abstract
- To provide high ranging precision in multipath environments, a ranging protocol should find the first arriving path, rather than the strongest path. We demonstrate a new attack vector that disrupts such precise Time-of-Arrival (ToA) estimation, and allows an adversary to decrease the measured distance by a value in the order of the channel spread (10-20 meters). This attack vector can be used in previously reported physical-communication-layer (PHY) attacks against secure ranging (or distance bounding). Furthermore, it creates a new type of attack based on malicious interference: This attack is much easier to mount than the previously known external PHY attack (distance-decreasing relay) and it can work even if secret preamble codes are used. We evaluate the effectiveness of this attack for a PHY that is particularly well suited for precise ranging in multipath environments: Impulse Radio Ultra-Wideband (IR-UWB). We show, with PHY simulations and experiments, that the attack is effective against a variety of receivers and modulation schemes. Furthermore, we identify and evaluate three types of countermeasures that allow for precise and secure ranging.
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| 2. |
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| 3. |
- Barreto, Sergio, et al.
(författare)
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Undetectable PMU Timing-Attack on Linear State-Estimation by UsingRank-1 Approximation
- 2018
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Ingår i: IEEE Transactions on Smart Grid. - : IEEE Press. - 1949-3053 .- 1949-3061. ; 9:4, s. 3530-3542
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Tidskriftsartikel (refereegranskat)abstract
- Smart-grid applications based on synchrophasor measurements have recently been shown to be vulnerable to timing attacks. A fundamental question is whether timing attacks could remain undetected by bad-data detection algorithms used in conjunction with state-of-the-art situational-awareness state estimators. In this paper, we analyze the detectability of timing attacks on linear state-estimation. We show that it is possible to forge delay attacks that are undetectable. We give a closed form for an undetectable attack; it imposes two phase offsets to two or more synchrophasor-based measurement units that can be translated to synchrophasors’ time delays. We also propose different methods for combining two-delays attacks to produce a larger impact. We simulate the attacks on a benchmark powertransmission grid, we show that they are successful and can lead to physical grid damage. To prove undetectability, we use classic bad-data detection techniques such as the largest normalized residual and the 2-test.
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| 4. |
- Buchegger, Sonja, et al.
(författare)
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A Test-Bed for Misbehavior Detection in Mobile Ad-hoc Networks : How Much can Watchdogs Really Do?
- 2004
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Ingår i: SIXTH IEEE WORKSHOP ON MOBILE COMPUTING SYSTEMS AND APPLICATIONS, PROCEEDINGS. - 0769522580 ; , s. 102-111
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Konferensbidrag (refereegranskat)abstract
- Several misbehavior detection and reputation systems have been proposed for mobile ad-hoc networks, relying on direct network observation mechanisms, so-called watchdogs. While these approaches have so far only been evaluated in simulations and restricted to selfish packet dropping, we are interested in the capabilities of a watchdog detection component in a real network. In this paper we present our test-bed implementation of misbehavior detection. Following an evaluation of both the feasibility and detectability of attacks on routing and forwarding in the Dynamic Source Routing (DSR) protocol, we present the design of our test-bed. In order to add detection capabilities, we extend the concept of passive acknowledgment by mechanisms for partial dropping, packet modification, and fabrication detection. We combine DSR with Netfilter and APE to enable detection. We implement both attackers and detection and show their feasibility and limitations.
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| 5. |
- Buchegger, Sonja
(författare)
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Coping with Misbehavior in Mobile Ad-hoc Networks
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- n this work, we address the question of how to enable a system to operate despite the presence of misbehavior. Specifically, in a mobile ad-hoc network, how can we keep the network functional for normal nodes when other nodes do not route and forward correctly? Node misbehavior due to selfish or malicious reasons or faulty nodes can significantly degrade the performance of mobile ad-hoc networks. Existing approaches such as economic incentives or secure routing by cryptographic means alleviate some of the problems, but not all. For instance, nodes can still forward packets on bogus routes. We propose a protocol called CONFIDANT (Cooperation Of Nodes --- Fairness In Dynamic Ad-hoc NeTworks) to cope with misbehavior. It enables nodes to detect misbehavior by first-hand observation and use of second-hand information provided by other nodes. The view a node has about the behavior of another node is captured in a reputation system, which is used to classify nodes as misbehaving or normal. Once a misbehaving node is detected, it is isolated from the network. Reputation systems can, however, be tricked by the spread of false reputation ratings, be it false accusations or false praise. Simple solutions such as exclusively relying on one`s own direct observations have drawbacks, as they do not make use of all the information available. To solve this problem, we propose a fully distributed reputation system that can cope with false information and effectively use second-hand information in a safe way. Our approach is based on a modified Bayesian estimation and classification procedure. In our approach, each node maintains a reputation rating and a trust rating about all other nodes it cares about. Reputation ratings capture the quality of the behavior of a node as an actor in the network performing routing and forwarding tasks. From time to time first-hand reputation information is exchanged with others; using a modified Bayesian approach we designed, second-hand reputation information is only accepted if it is compatible with the current reputation rating. Reputation ratings are only slightly modified by accepted information. Trust ratings capture the quality of a node as an actor in the reputation system and reflect whether the reported first hand information summaries published by node are likely to be true. Trust ratings are updated based on the compatibility of second-hand reputation information with prior reputation ratings. We enable node redemption and prevent the sudden exploitation of good reputation built over time by introducing reputation fading. Data is entirely distributed, the reputation and trust value of a node is the collection of ratings maintained by others. We use simulation to evaluate and demonstrate the performance. We found that CONFIDANT can keep the network performance high even when up to half of the network population misbehaves. We show that our approach of using second-hand information significantly speeds up the detection of misbehaving nodes while keeping the number of false positives and negatives negligibly low.
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| 6. |
- Buchegger, Sonja, et al.
(författare)
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Reputation Systems for Self-Organized Networks
- 2008
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Ingår i: IEEE technology & society magazine. - 0278-0097 .- 1937-416X. ; 27:1, s. 41-47
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Tidskriftsartikel (refereegranskat)abstract
- Self-organized networks such as mobile ad-hoc, Internet-based peer-to-peer, wireless mesh and Fourth generation (4G) Wireless networks, have been receiving increase attention, both deployment and research. However, there is one major issue in suchself-organized communication systems which is "cooperation". These networks depend on cooperation of nodes. Addressing this issue, reputation system, proven to be useful and have been studied and applied separately in diverse disciplines such as economics, computer science, and social science, help nodes decide with whom to cooperate and which nodes to avoid. This system is offering a way of collecting information about the entity of interest, of updating it, and of incorporating the information about that entity obtained from others. It provides the basis of decision making itself, allowing nodes to chose other nodes for cooperation.
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| 7. |
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| 8. |
- Buchegger, Sonja, et al.
(författare)
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Self-policing mobile ad-hoc networks by reputation systems
- 2005
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Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 43:7, s. 101-107
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Tidskriftsartikel (refereegranskat)abstract
- Node misbehavior due to selfish or malicious reasons or faulty nodes can significantly degrade the performance of mobile ad-hoc networks. To cope with misbehavior in such self-organized networks, nodes need to be able to automatically adapt their strategy to changing levels of cooperation. Existing approaches such as economic incentives or secure routing by cryptography alleviate some of the problems, but not all. We describe the use of a self-policing mechanism based on reputation to enable mobile ad-hoc networks to keep functioning despite the presence of misbehaving nodes. The reputation system in all nodes makes them detect misbehavior locally by observation and use of second-hand information. Once a misbehaving node is detected it is automatically isolated from the network. We classify the features of such reputation systems and describe possible implementations of each of them. We explain in particular how it is possible to use second-hand information while mitigating contamination by spurious ratings.
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| 9. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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On the Asymptotic Validity of the Decoupling Assumption for Analyzing 802.11 MAC Protocol
- 2012
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Ingår i: IEEE Transactions on Information Theory. - : IEEE Press. - 0018-9448 .- 1557-9654. ; 58:11, s. 6879-6893
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Tidskriftsartikel (refereegranskat)abstract
- Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. This decoupling assumption results from mean field convergence and is generally true in transient regime in the asymptotic sense (when the number of wireless nodes tends to infinity), but, contrary to widespread belief, may not necessarily hold in stationary regime. The issue is often related with the existence and uniqueness of a solution to a fixed point equation; however, it was also recently shown that this condition is not sufficient; in contrast, a sufficient condition is a global stability property of the associated ordinary differential equation. In this paper, we give a simple condition that establishes the asymptotic validity of the decoupling assumption for the homogeneous case (all nodes have the same parameters). We also discuss the heterogeneous and the differentiated service cases and formulate a new ordinary differential equation. We show that the uniqueness of a solution to the associated fixed point equation is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid in the asymptotic sense in stationary regime.
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| 10. |
- Cho, Jeong-woo, 1978-, et al.
(författare)
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On the Validity of the Fixed Point Equation and Decoupling Assumption for Analyzing the 802.11 MAC Protocol
- 2010
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Ingår i: Performance Evaluation Review. - : Association for Computing Machinery (ACM). - 0163-5999 .- 1557-9484. ; 38:2, s. 36-38
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Tidskriftsartikel (refereegranskat)abstract
- Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. A necessary condition for the validity of this approach is the existence and uniqueness of a solution to a fixed point equation. However, it was also recently pointed out that this condition is not sufficient; in contrast, a necessary and sufficient condition is a global stability property of the associated ordinary differential equation. Such a property was established only for a specific case, namely for a homogeneous system (all nodes have the same parameters) and when the number of backoff stages is either 1 or infinite and with other restrictive conditions. In this paper, we give a simple condition that establishes the validity of the decoupling assumption for the homogeneous case. We also discuss the heterogeneous and the differentiated service cases and show that the uniqueness condition is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid
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