Abstract

This work presents the results of the on-going International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) J02017 entitled Enhancing Computer Security for Radiation Detection Systems. Radiation detection systems are comprised of a large number of fixed and mobile radiation detectors used for safety and security purposes for nuclear power energy production, nuclear fuel cycle activities, nuclear research reactor operation, medical applications, transportation of nuclear material, environmental monitoring, border control and major public events (among others). The signals generated by radiation detection and physical protection systems produce alarms (and information) that are transmitted and monitored locally or remotely and additional alarm monitoring centers. The transmission of this information across a diverse range of communication channels increases the effectiveness of radiation monitoring and detection systems, and the timely responses to alarm conditions. During signal generation and transmission, processing or storage of information, there is the possibility of compromise and manipulation of data, requiring computer security measures to protect and preserve the confidentiality, integrity, and availability of the information being transmitted, assessed, and stored. The research also includes the physical protection systems that protect other radioactive material from theft or sabotage. The objective of the IAEA CRP on Enhancing Computer Security for Radiation Detection Systems is to develop methodologies and techniques to improve computer security of radiation detection equipment, physical protection systems, associated computer-based systems, data communications protocols and the network infrastructure that supports the use of these systems. This panel will discuss the ongoing IAEA CRP research addressing computer security issues related to radiation detection equipment, the need of cybersecurity capacity in specific nuclear security domains; the specific challenges involved with researching cybersecurity for nuclear security; and it will summarize key projects within the IAEA CRP J02017 and their potential benefits to capacity building efforts in Member States with mature nuclear security programs and newcomer countries.

Keywords

protocol reverse engineering, protocol state machine, performance evaluation, runtime analysis, bounded runtime, incomplete input

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Abstract

Having access to the specifications of network pro- tocols is essential for several reasons in IT security. When the specifications are not known, one may turn to protocol reverse engineering methods to reconstruct these, typically by analysing recorded network traffic or inspecting an executable that implements the protocol. First, the format and structure of the messages need to be recovered, then the state machine of the protocol itself. Over the years, several solutions have been proposed for both tasks. As a consequence, picking the right solution for a given scenario is often a complex problem that involves evaluating and comparing various solutions. In this paper, we review the current means of evaluating the perfor- mance of protocol state machine reverse engineering methods. To help alleviate the shortcomings of the current methodology, we propose two new metrics of performance to be measured: correctness and completeness of output for partial runs (when runtime is bounded). These, combined with previously used metrics should make it easier to pick the most ideal choice for a given use case. We also propose the examination of cases where the algorithms have to work with incomplete or inaccurate syntactical information. We showcase how these new metrics and related information may be useful for the evaluation and comparison of various algorithms by applying these new methods to evaluate the performance of a recent protocol state machine reverse engineering method.

Keywords

electric power system, critical infrastructure, cyberattack

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Abstract

All developed countries are highly dependent on the operation of electric power systems, and this dependence will probably increase. Many factors influence stable operation, some of which are random (weather or failures of devices and cables); however, human activities also have a significant impact on reliability. In this paper, we deal with special cases of attacks that achieve a detrimental effect on the electric power system by compromising the controlling and monitoring computer systems. To support the reader, we first analyze the key components of the physical and cyber parts of the system to provide an understanding of the intertwining of these domains – it is a cyber-physical system. We further elaborate on how an event can spread from one part to the other through domains. Then, a series of actual examples underlines the importance of this topic, focusing on malicious acts committed with the goal of sabotaging the power system. Thereafter, we analyze cyber-attacks committed during the last eight years in Ukraine. Most of these attacked the Ukrainian electric power system, aiming for blackouts and device destruction. Some of the attacks had severe consequences in other European countries as well. However, some attacks were successfully stopped before any harm was made. After analyzing the events, we conclude that threat actors’ focus shifted from causing short-term blackouts to device destruction and long-term breakdowns. In the last part of our paper, we enumerate mitigation methods for operators. Our enumeration is based on the PreDeCo principle, namely prevention, detection, and correction. In conclusion, the defender must separate its different purpose networks, use strong authentication and authorization, and have proper patch management policies. These techniques must be verified with regular penetration tests. As the Ukrainian examples show, the threat actor sometimes can avoid prevention techniques; thus, good detection is necessary. The detection is based on analyzing the output of intrusion detection systems and detailed logging facilities. The analysis should be done in the security operations center by experts with knowledge of both cyberspace and electric power systems operations. In case of an incident, the security operations center must make corrective steps with the possible help of external experts. The corrective steps include the understanding of the incident, the recovery from the incident, the prevention of future similar incidents, and the digital forensic of the incident.

Keywords

IEC 60870-5-104, Attack, Security, Power system

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Abstract

IEC 60870-5-104 is a widely used protocol for telecontrol in European power systems. However, security was not a design goal when it was originally published: This protocol lacks built-in security features such as encryption, integrity protection, or authentication. In this paper, we describe novel types of attacks against the protocol in a holistic way. Therefore, we also enumerate the possible entry points of the threat actors and demonstrate a new technique, where the malicious actor can precisely target the attack. These methods are demonstrated both on simulated environment and actual devices and compared with already published methods.

Keywords

machine learning, time series, radiation detection system

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Abstract

We need a lot of data for various purposes. We want to test new algorithms or make a cyber exercise, but sometimes we do not have enough original publicly available data. In this case we must generate synthetic data. A special case of data generation is where we need a time series. This paper discovers different methods of time series generation and test a method called TimeGAN for generating synthetic radiation detection system data. Similar approach can be used for temperature, pressure, or other synthetic time series relevant for the nuclear industry.

Keywords

In-vehicle network data; Privacy attacks; Driver re-identification; Trajectory reconstruction; Anonymization; Differential privacy

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Abstract

The ever-increasing volume of vehicular data has enabled different service providers to access and monetize in-vehicle network data of millions of drivers. However, such data often carry personal or even potentially sensitive information, and therefore service providers either need to ask for drivers\' consent or anonymize such data in order to comply with data protection regulations. In this paper, we show that both fine-grained consent control as well as the adequate anonymization of in-network vehicular data are very challenging. First, by exploiting that in-vehicle sensor measurements are inherently interdependent, we are able to effectively i) re-identify a driver even from the raw, unprocessed CAN data with 97% accuracy, and ii) reconstruct the vehicle's complete location trajectory knowing only its speed and steering wheel position. Since such signal interdependencies are hard to identify even for data controllers, drivers' consent will arguably not be informed and hence may become invalid. Second, we show that the non-systematic application of different standard anonymization techniques (e.g., aggregation, suppression, signal distortion) often results in volatile, empirical privacy guarantees to the population as a whole but fails to provide a strong, worst-case privacy guarantee to every single individual. Therefore, we advocate the application of principled privacy models (such as Differential Privacy) to anonymize data with strong worst-case guarantee.

Keywords

IEC-104, attack, security, power grid

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Abstract

IEC 60870-5-104 is a widely used protocol for telecontrol in European power systems. Despite its wide usage, security was not a priority when the protocol was created. The IEC-104 protocol lacks important security features such as encryption, integrity protection, or authentication. In this paper, our goal is to show the risks of using this insecure protocol. To demonstrate it, we designed and implemented a wide range of different attacks. We also rated the stealthiness of these attacks in order to show that detection of an intruder is not always obvious. Our stealthy and successful attacks were carried out in a test environment with several virtual machines running an open-source implementation of the protocol.

Keywords

NPP Cybersecurity, I&C Security, SIEM, IDS, Anomaly Detection

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Abstract

Nuclear power plants (NPPs) are implementing or transitioning to digital instrumentation and control (I&C) systems to control underlying physical processes. Such systems present an attack surface of obvious interest to various subsets of potential attackers and hence lead to a relevance of cybersecurity in a nuclear context. This prompts the need for measures aimed at detecting anomalous behavior or unwanted events in the I&C systems. This paper performs a survey on existing approaches to detect such behavior. This survey covers different perspectives and a broad range of different anomalous or unwanted behavior in the physical process and all aspects of the digital I&C systems. The perspective benefits from the inclusion of experts from the field of NPP cybersecurity, automation engineering and IT security. This interdisciplinary perspective allows for the identification of different sets of relevant data and events which might contribute to the understanding of an abnormal or unwanted situation (malfunction or a cyber-attack). This paper discusses how this data should be collected, how it can be aggregated and in which way it can enhance the safety and security of digital I&C systems.

Keywords

automated protocol reverse engineering, state machines, Mealy machines

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Abstract

In this work, we propose a novel solution to the problem of inferring the state machine of an unknown protocol. We extend and improve prior results on inferring Mealy machines, and present a new algorithm that accesses and interacts with a networked system that runs the unknown protocol in order to infer the Mealy machine representing the protocol’s state machine. To demonstrate the viability of our approach, we provide an implementation and illustrate the operation of our algorithm on a simple example protocol, as well as on two real-world protocols, Modbus and MQTT.

Keywords

protocol reverse engineering, message format, field semantics, inference, binary protocols, network traffic, graph analysis, Modbus, MQTT

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Abstract

Protocol specifications describe the interaction be- tween different entities by defining message formats and message processing rules. Having access to such protocol specifications is highly desirable for many tasks, including the analysis of botnets, building honeypots, defining network intrusion detection rules, and fuzz testing protocol implementations. Unfortunately, many protocols of interest are proprietary, and their specifications are not publicly available. Protocol reverse engineering is an approach to reconstruct the specifications of such closed proto- cols. Protocol reverse engineering can be tedious work if done manually, so prior research focused on automating the reverse engineering process as much as possible. Some approaches rely on access to the protocol implementation, but in many cases, the protocol implementation itself is not available or its license does not permit its use for reverse engineering purposes. Hence, in this paper, we focus on reverse engineering protocol specifications relying solely on recorded network traffic. More specifically, we propose GrAMeFFSI, a method based on graph analysis that can infer protocol message formats as well as certain field semantics for binary protocols from network traces. We demonstrate the usability of our approach by running it on packet captures of two known protocols, Modbus and MQTT, then comparing the inferred specifications to the official specifications of these protocols.

Abstract

The paper presents the development of an architecture to deploy a simulated nuclear power plant in order to support training and research. In contrast to other simulators, which focus on the underlying physical processes, this approach also covers the industrial control systems (ICS) supervising and controlling these processes. Additionally, the IT components required for the associated business processes are also included, allowing for training with regard to threats to these IT components, including cyber-attack scenarios.

Abstract

In this work, we are addressing the problem of inferring the state machine of an unknown protocol. Our method is based on prior work on inferring Mealy machines. We require access to and interaction with a system that runs the unknown protocol, and we serve a state-of-the-art Mealy machine inference algorithm with appropriate input obtained from the system at hand. We implemented our method and illustrate its operation on a simple example protocol.

Abstract

Nuclear power plants use different digital assets to control the processes. These assets are normally connected by computer networks, and are targets of potential cyber-attacks. To avoid or mitigate the effect of such an attack, different security controls are used in accordance with the guidelines. Before deploying a new cyber security control, it must be tested thoroughly. The paper proposes virtual testbeds made of virtual computers and networks for these tests and shows how three widely used open source firewalls perform in such a test.

Keywords

protocol reverse engineering; message format; field semantics; inference; binary protocols; network traffic; Modbus; MQTT

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Abstract

Protocol specifications describe the interaction between different entities by defining message formats and message processing rules. Having access to such protocol specifications is highly desirable for many tasks, including the analysis of botnets, building honeypots, defining network intrusion detection rules, and fuzz testing protocol implementations. Unfortunately, many protocols of interest are proprietary, and their specifications are not publicly available. Protocol reverse engineering is an approach to reconstruct the specifications of such closed protocols. Protocol reverse engineering can be tedious work if done manually, so prior research focused on automating the reverse engineering process as much as possible. Some approaches rely on access to the protocol implementation, but in many cases, the protocol implementation itself is not available or its license does not permit its use for reverse engineering purposes. Hence, in this paper, we focus on reverse engineering protocol specifications based solely on recorded network traffic. More specifically, we propose a method that can infer protocol message formats as well as certain field semantics for binary protocols from network traces. We demonstrate the usability of our approach by running it on packet captures of two known protocols, Modbus and MQTT, then comparing the inferred specifications to the known specifications of these protocols.

Keywords

Digital forensics, CAN network

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Abstract

Accident reconstruction is the process of reliably discovering what has happened before a serious event. We show how the most widely used intra vehicular network (namely the Controller Area Network, CAN) can be used in this process. We show how the actual velocity and steering wheel position transmitted on the CAN network can be used to reconstruct the trajectory of a vehicle. This trajectory is an essential input in the reconstruction process. In this paper, we show how the CAN traffic of an actual vehicle can be used to recon- struct the trajectory of the vehicle, and we evaluate our approach in several real life experiments including normal and pre-accident situations.

Abstract

Cyber physical systems (CPS) are used to control chemical processes, and can be found in manufacturing, civil infrastructure, energy industry, transportation and in many more places. There is one common characteristic in these areas, their operation is critical as a malfunction can potential be life-threatening. In the past, an attack against the cyber part of the systems can lead to physical consequences. The first well known attack against a CPS was Stuxnet in 2010. It is challenging to develop countermeasures in this field without endangering the normal operation of the underlying system. In our research, our goal was to detect attacks without interfering with the cyber physical systems in any way. This can be realized by an anomaly detection system using passive network monitoring. Our approach is based on analysing the state of the physical process by interpreting the communication between the control system and the supervisory system. This state can be compared to a model based prediction of the system, which can serve as a solid base for intrusion detection. In order to realize our intrusion detection system, a testbed was built based on widely used Siemens PLCs. Our implementation consists of three main parts. The first task is to understand the network communication in order to gain information about the controlled process. This was realized by analysing and deeply understanding the publicly undocumented Siemens management protocol. The resulting protocol parser was integrated into the widely-used Bro network security monitoring framework. Gathering information about the process state for a prolonged time creates time series. With these time series, as the second step, statistical models of the physical process can be built to predict future states. As the final step, the new states of the physical process can be compared with the predicted states. Significant differences can be considered as an indicator of compromise.

Abstract

Abstract

Abstract

Abstract

Keywords

PLC honeypot, critical infrastructures, advanced threat monitoring, industrial control systems security

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Abstract

Smart grids consist of suppliers, consumers, and other parts. The main suppliers are normally supervised by industrial control sys- tems. These systems rely on programmable logic controllers (PLCs) to control industrial processes and communicate with the supervisory sys- tem. Until recently, industrial operators relied on the assumption that these PLCs are isolated from the online world and hence cannot be the target of attacks. Recent events, such as the infamous Stuxnet attack [15] directed the attention of the security and control system community to the vulnerabilities of control system elements, such as PLCs. In this paper, we design and implement the Crysys PLC honeypot (CryPLH) system to detect targeted attacks against industrial control systems. This PLC honeypot can be implemented as part of a larger security monitoring system. Our honeypot implementation improves upon existing solutions in several aspects: most importantly in level of interaction and ease of configuration. Results of an evaluation show that our honeypot is largely indistinguishable from a real device from the attacker’s perspective. As a collateral of our analysis, we were able to identify some security issues in the real PLC device we tested and implemented specific firewall rules to protect the device from targeted attacks.

Abstract

In the past few years, research interest has been increased towards wireless sensor networks (WSNs) and their application in both the military and civil domains. To support scalability in WSNs and increase network lifetime, nodes are often grouped into disjoint clusters. However, secure and reliable clustering, which is critical in WSNs deployed in hostile environments, has gained modest attention so far or has been limited only to fault tolerance. In this paper, we review the state-of-the-art of clustering protocols inWSNs with special emphasis on security and reliability issues. First, we define the taxonomy of security and reliability for cluster head election and clustering in WSNs. Then, we describe and analyze the most relevant secure and reliable clustering protocols. Finally, we propose countermeasures against typical attacks and show how they improve the discussed protocols.

Abstract

In this paper, we study the problem of traffic analysis attacks in wireless body area sensor networks. When these networks are used in health-care for remote patient monitoring, traffic analysis can reveal the type of medical sensors mounted on the patient, and this information may be used to infer the patient’s health problems. We show that simple signal processing methods can be used effectively for performing traffic analysis attacks and identifying the sensor types in a rather weak adversary model. We then investigate possible traffic obfuscation mechanisms aiming at hiding the regular patterns in the observable wireless traffic. Among the investigated countermeasures, traffic shaping, a mechanism that introduces carefully chosen delays for message transmissions, appears to be the best choice, as it achieves close to optimal protection and incurs no overhead.

Abstract

In mission critical cyber-physical systems, dependability is an important requirement at all layers of the system architecture. In this paper, we propose protocols that increase the dependability of wireless sensor networks, which are potentially useful building blocks in cyber physical systems. More specifically, we propose two private aggregator node election protocols, a private data aggregation protocol, and a corresponding private query protocol for sensor networks that allow for secure in-network data aggregation by making it difficult for an adversary to identify and then physically disable the designated aggregator nodes. Our advanced protocols resist strong adversaries that can physically compromise some nodes.

Abstract

Designing a routing protocol for large low-power and lossy networks (LLNs), consisting of thousands of con-strained nodes and unreliable links, presents new challenges. The IPv6 Routing Protocol for Low-power and Lossy Networks (RPL), have been developed by the IETF ROLL Working Group as a preferred routing protocol to provide IPv6 routing functionality in LLNs. RPL provides path diversity by building and maintaining directed acyclic graphs (DAG) rooted at one (or more) gateway. However, an adversary that impersonates a gateway or has compromised one of the nodes close to the gateway can divert a large part of network traffic forward itself and/or exhaust the nodes’ batteries. Therefore in RPL, special security care must be taken when the Destination Oriented Directed Acyclic Graph (DODAG) root is updating the Version Number by which reconstruction of the routing topology can be initiated. The same care also must be taken to prevent an internal attacker (compromised DODAG node) to publish decreased Rank value, which causes a large part of the DODAG to connect to the DODAG root via the attacker and give it the ability to eavesdrop a large part of the network traffic forward itself. Unfortunately, the currently available security services in RPL will not protect against a compromised internal node that can construct and disseminate fake messages. In this paper, a new security service is described that prevents any misbehaving node from illegitimately increasing the Version Number and compromise illegitimate decreased Rank values.

Abstract

A delay-tolerant network is a mobile ad hoc network where the message dissemination is based on the store-carry-and-forward principle. This principle raises new aspects of the privacy problem. In particular, an attacker can build a user profile and trace the nodes based on this profile even if the message exchange protocol provides anonymity. In this paper, an attacker model is presented and some proposed attackers are implemented. We analyze the efficiency of both the attacks and the proposed defense mechanism, called Hide-and-Lie Strategy. We show that without any defense mechanism, the nodes are traceable, but with the Hide-and-Lie Strategy, the success probability of an attacker can be made equal to the success probability of the simple guessing. Furthermore, in some scenarios, the Hide-and-Lie Strategy increases the message delivery ratio. The number of downloaded messages and the maximal memory size required to apply the proposed privacy defense mechanism is also investigated.

Abstract

Clustering and data aggregation in wireless sensor networks improves scalability, and helps the efficient use of scarce resources. Yet, these mechanisms also introduce some security issues; in particular, aggregator nodes become attractive targets of physical destruction and jamming attacks. In order to mitigate this problem, we propose a new private aggregator node election protocol that hides the identity of the elected aggregator nodes both from external eavesdroppers and from compromised nodes participating in the protocol. We also propose a private data aggregation protocol and a corresponding private query protocol which allows the aggregators to collect sensor readings and respond to queries of the base station, respectively, without revealing any useful information about their identity to external eavesdroppers and to compromised nodes.

Abstract

Clustering is a useful mechanism in wireless sensor networks that helps to cope with scalability problems and, if combined with in-network data aggregation, may increase the energy efficiency of the network. At the same time, by assigning a special role to the cluster head nodes, clustering makes the network more vulnerable to attacks. In particular, disabling a cluster head by physical destruction or jamming may render the entire cluster inoperable temporarily until the problem is detected and a new cluster head is elected. Hence, the cluster head nodes may be attractive targets of attacks, and one would like to make it difficult for an adversary to identify them. The adversary can try to identify the cluster head nodes in various ways, including the observation of the cluster head election process itself and the analysis of the traffic patterns after the termination of the cluster head election. In this paper, we focus on the former problem, which we call the private cluster head election problem. This problem has been neglected so far, and as a consequence, existing cluster head election protocols leak too much information making the identification of the elected cluster head nodes easy even for a passive external observer. We propose the first private cluster head election protocol for wireless sensor networks that is designed to hide the identity of the elected cluster head nodes from an adversary that can observe the execution of the protocol.

Keywords

vehicular ad hoc network, security, privacy

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Abstract

Abstract

Untraceability of vehicles is an important requirement in future vehicle communications systems. Unfortunately, heartbeat messages used by many safety applications provide a constant stream of location data, and without any protection measures, they make tracking of vehicles easy even for a passive eavesdropper. One commonly known solution is to transmit heartbeats under pseudonyms that are changed regularly in order to obfuscate the trajectory of vehicles. However, this approach is effective only if some silent period is kept during the pseudonym change and several vehicles change their pseudonyms nearly at the same time and at the same location. Unlike previous works that proposed explicit synchronization between a group of vehicles and/or required pseudonym change in a designated physical area (i.e., a static mix zone), we propose a much simpler approach that does not need any explicit cooperation between vehicles and any infrastructure support. Our basic idea is that vehicles should not transmit heartbeat messages when their speed drops below a given threshold, say 30 km/h, and they should change pseudonym during each such silent period. This ensures that vehicles stopping at traffic lights or moving slowly in a traffic jam will all refrain from transmitting heartbeats and change their pseudonyms nearly at the same time and location. Thus, our scheme ensures both silent periods and synchronized pseudonym change in time and space, but it does so in an implicit way. We also argue that the risk of a fatal accident at a slow speed is low, and therefore, our scheme does not seriously impact safety-of- life. In addition, refraining from sending heartbeat messages when moving at low speed also relieves vehicles of the burden of verifying a potentially large amount of digital signatures, and thus, makes it possible to implement vehicle communications with less expensive equipments.

Abstract

Significant developments have taken place over the past few years in the area of vehicular communication systems. Now, it is well understood in the community that security and protection of private user information are a prerequisite for the deployment of the technology. This is so precisely because the benefits of VC systems, with the mission to enhance transportation safety and efficiency, are at stake. Without the integration of strong and practical security and privacy enhancing mechanisms, VC systems can be disrupted or disabled, even by relatively unsophisticated attackers. We address this problem within the SeVeCom project, having developed a security architecture that provides a comprehensive and practical solution. We present our results in a set of two articles in this issue. In this first one, we analyze threats and types of adversaries, identify security and privacy requirements, and present a spectrum of mechanisms to secure VC systems. We provide a solution that can be quickly adopted and deployed. In the second article we present our progress toward the implementation of our architecture and results on the performance of the secure VC system, along with a discussion of upcoming research challenges and our related current results.

Abstract

We propose a novel authentication scheme that ensures privacy of the provers. Our scheme is based on symmetric-key cryptography, and therefore, it is well-suited to resource constrained applications in large scale environments. A typical example for such an application is an RFID system, where the provers are low-cost RFID tags, and the number of the tags can potentially be very large. We analyze the proposed scheme and show that it is superior to the well-known key-tree based approach for private authentication both in terms of privacy and efficiency.

Abstract

The promise of vehicular communications is to make road traffic safer and more efficient. However, besides the expected benefits, vehicular communications also introduce some privacy risk by making it easier to track the physical location of vehicles. One approach to solve this problem is that the vehicles use pseudonyms that they change with some frequency. In this paper, we study the effectiveness of this approach.We define a model based on the concept of the mix zone, characterize the tracking strategy of the adversary in this model, and introduce a metric to quantify the level of privacy enjoyed by the vehicles. We also report on the results of an extensive simulation where we used our model to determine the level of privacy achieved in realistic scenarios. In particular, in our simulation, we used a rather complex road map, generated traffic with realistic parameters, and varied the strength of the adversary by varying the number of her monitoring points. Our simulation results provide detailed information about the relationship between the strength of the adversary and the level of privacy achieved by changing pseudonyms.

Abstract

Key-tree based private authentication has been proposed by Molnar and Wagner as a neat way to efficiently solve the problem of privacy preserving authentication based on symmetric key cryptography. However, in the key-tree based approach, the level of privacy provided by the system to its members may decrease considerably if some members are compromised. In this paper, we analyze this problem, and show that careful design of the tree can help to minimize this loss of privacy. First, we introduce a benchmark metric for measuring the resistance of the system to a single compromised member. This metric is based on the well-known concept of anonymity sets. Then, we show how the parameters of the key-tree should be chosen in order to maximize the system's resistance to single member compromise under some constraints on the authentication delay. In the general case, when any member can be compromised, we give a lower bound on the level of privacy provided by the system. We also present some simulation results that show that this lower bound is quite sharp. The results of this paper can be directly used by system designers to construct optimal key-trees in practice; indeed, we consider this as the main contribution of our work.

Abstract

Abstract

Sensor networks are large scale networks consisting of several nodes and some base stations. The nodes are monitoring the environment and send their measurement data towards the base stations possibly via multiple hops. Since the nodes are often battery powered, an important design criterion for sensor networks is the maximization of their lifetime. In this paper, we consider multi-domain sensor networks, by which we mean a set of sensor networks that co-exist at the same physical location but run by different authorities. In this setting, the lifetime of all networks can be increased if the nodes cooperate and also forward packets originating from foreign domains. There is a risk, however, that a selfish network takes advantage of the cooperativeness of the other networks and exploits them. We study this problem in a game theoretic setting, and show that, in most cases, there is a Nash equilibrium in the system, in which at least one of the strategies is cooperative, even without introducing any external incentives (e.g., payments).

Abstract

Cikkünkben bevezetjük a kooperációra való ösztönzés problémáját, ami tipikus problémaként jelentkezik a többugrásos vezetéknélküli hálózatokban. Röviden áttekintjük a nem-kooperatív viselkedési fajtákat, és a kooperációra ösztönzõ mechanizmusok típusait. Végül összefoglaljuk két általunk javasolt ösztönzõ mechanizmus fõbb elemeit, ötleteit.