Trust Computations and Trust Dynamics in Mobile Adhoc Networks: A Survey
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paper_title: Using trust for secure collaboration in uncertain environments

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The SECURE project investigates the design of security mechanisms for pervasive computing based on trust. It addresses how entities in unfamiliar pervasive computing environments can overcome initial suspicion to provide secure collaboration.
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paper_title: Location-based trust for mobile user-generated content: applications, challenges and implementations

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The recent explosion in shared media content and sensed data produced by mobile end-users is challenging well-established principles and assumptions in data trust models. A fundamental issue we address in this paper is how to establish some trust level in the authenticity of content created by untrusted mobile users. We advocate a secure localization and certification service that allows content producers to tag their content with with a spatial times-tamp indicating its physical location. At the same time, however, our approach preserves the privacy of producers by not exposing their identity to the potential content consumers. We provide a list of existing and possible applications that would profit from such a secure localization service and sketch possible implementations of the service, highlighting advantages and drawbacks.
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paper_title: Misbehavior Detection Using Implicit Trust Relations in the AODV Routing Protocol

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Trust is one of the basic assumptions that we use in every day life. In ad hoc networks, routing protocols implement trust implicitly between the nodes of the network. Unfortunately, the implicit trust relations are not used by nodes whereas the attacks on ad hoc routing protocols precisely lead to the violation of at least one of these trust relations.In this paper, we demonstrate that a node can use these implicit trust relations to reason on neighbor behaviors to detect malicious nodes. We first formalize implicit trust relations of the AODV protocol. Then, we show that, given these relations, a node is able to reason on the actions performed by its neighbors and so deduce information about their knowledge. Finally, we discuss how these relations and the deduced information can be used to supervise the neighbor behavior and detect malicious nodes.
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paper_title: A survey of secure mobile Ad Hoc routing protocols

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Several routing protocols have been proposed in recent years for possible deployment of mobile ad hoc networks (MANETs) in military, government and commercial applications. In this paper, we review these protocols with a particular focus on security aspects. The protocols differ in terms of routing methodologies and the information used to make routing decisions. Four representative routing protocols are chosen for analysis and evaluation including: Ad Hoc on demand Distance Vector routing (AODV), Dynamic Source Routing (DSR), Optimized Link State Routing (OLSR) and Temporally Ordered Routing Algorithm (TORA). Secure ad hoc networks have to meet five security requirements: confidentiality, integrity, authentication, non-repudiation and availability. The analyses of the secure versions of the proposed protocols are discussed with respect to the above security requirements.
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paper_title: Trust-based security for wireless ad hoc and sensor networks

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Wireless sensors networks are susceptible to a large number of security threats, and because of the communication, computation and delay constraints of most applications that run on top of these networks, traditional security mechanisms cannot be used. Trust and reputation have been recently suggested as an effective security mechanism for open environments such as the Internet, and considerable research has been done on modeling and managing trust and reputation. Using the trust and reputation management scheme to secure wireless sensor networks (WSNs) requires paying close attention to the incurred bandwidth and delay overhead, which have thus far been overlooked by most research work. In this paper, we propose a novel agent-based trust and reputation management scheme (ATRM) for wireless sensor networks. The objective of the scheme is to manage trust and reputation locally with minimal overhead in terms of extra messages and time delay. Throughout the entirety of this paper, we describe our scheme and prove its correctness. We will also present our extensive performance evaluation results, which clearly show that trust and reputation can be computed in wireless sensor networks with minimal overhead.
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paper_title: A survey on distributed approaches to graph based reputation measures

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Reputation systems are indispensable for the operation of Internet mediated services, electronic markets, document ranking systems, P2P networks and Ad Hoc networks. Here we survey available distributed approaches to the graph based reputation measures. Graph based reputation measures can be viewed as random walks on directed weighted graphs whose edges represent interactions among peers. We classify the distributed approaches to graph based reputation measures into three categories. The first category is based on asynchronous methods. The second category is based on the aggregation/decomposition methods. And the third category is based on the personalization methods which use the information available locally.
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paper_title: Markov Chain Trust Model for Trust-Value Analysis and Key Management in Distributed Multicast MANETs

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To increase efficiency in mobile ad hoc networks (MANETs), the multicast MANET is proposed for a sender that sends packets to several receivers through a multicast session. In MANETs, multicast group members frequently change due to node mobility; thus, supporting secure authentication and authorization in a multicast MANET is more critical than that in a wired network with a centralized certificate authentication (CA) server. This paper thus proposes a two-step secure authentication approach for multicast MANETs. First, a Markov chain trust model is proposed to determine the trust value (TV) for each one-hop neighbor. A node's TV is analyzed from its previous trust manner that was performed in this group. The proposed trust model is proven as an ergodic continuous-time Markov chain model. Second, the node with the highest TV in a group will be selected as the CA server. To increase reliability, the node with the second highest TV will be selected as the backup CA server that will take over CA when CA fails. The procedures of the secure authentication for group management are detailed. The security analysis of each procedure is analyzed to guarantee that the proposed approach achieves a secure reliable authentication in multicast MANETs. In addition, several famous attacks have been analyzed and discussed. Numerical results indicate that the analytical TV of each mobile node is very close to that of simulation under various situations. The speed of the convergence of the analytical TV shows that the analyzed result is independent of initial values and trust classes. This is a good feature of analytical models.
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paper_title: Modeling and Analysis of Trust Management for Cognitive Mission-Driven Group Communication Systems in Mobile Ad Hoc Networks

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We develop and analyze a trust management protocol for cognitive mission-driven group communication systems (GCSs) in mobile ad hoc networks (MANETs) using hierarchical modeling techniques based on stochastic Petri nets. The goal is to efficiently establish acceptable trust levels among mobile nodes without prior interactions. We seek to identify the optimal length of a trust chain among peers in a trust web so as to maximize the trust levels for peers on the trust chain, by trading off trust space for trust level. The cognitive nodes in the network can dynamically adapt to changing network environments by adjusting their design parameter settings over time to establish an acceptable trust level with other nodes. We define a trust metric that captures unique characteristics of trust concepts in such MANETs. We demonstrate that an optimal trust chain exists for maximizing the trust metric.
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paper_title: Trust-Based Fast Authentication for Multiowner Wireless Networks

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In multiowner wireless networks, access points (APs) are owned and operated by different administrations, leading to significant authentication delays during handoff between APs. We propose to exploit the trust between the owners of neighboring APs for reducing the authentication delay. In the proposed authentication scheme, neighboring APs that trust each other share the security key for the visiting node to avoid lengthy authentication routines each time the visiting node switches APs. The performance of the proposed trust-based authentication scheme is evaluated using a Markov model. Using numerical experiments, we first study a basic scenario where mobile nodes are not aware of the trust networks that exist in a given neighborhood. Subsequently, we consider an advanced scenario where a mobile node functionality is augmented to discover the trust network so as to minimize roaming beyond the trusted APs. We find that, even with the basic implementation, the average number of full authentications needed for a roaming mobile reduces linearly as the likelihood of two neighboring APs trusting each other increases. With the advanced implementation, our experiments show that quadratic reduction is achieved. The Markov model is validated using discrete event simulation.
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paper_title: Trust and the appraisal process in close relationships.

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A lifting apparatus wherein a cone rack mechanism having cone pieces interlocked to driving gears is driven by such driving gears, which are connected and controlled by a special friction clutch mechanism, a latch mechanism, and a centrifugal brake, for continuing the lifting and lowering of a body, such as a water gate.
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paper_title: Affect- and Cognition-Based Trust as Foundations for Interpersonal Cooperation in Organizations

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This study addressed the nature and functioning of relationships of interpersonal trust among managers and professionals in organizations, the factors influencing trust's development, and the implications of trust for behavior and performance. Theoretical foundations were drawn from the sociological literature on trust and the social-psychological literature on trust in close relationships. An initial test of the proposed theoretical framework was conducted in a field setting with 194 managers and professionals.
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paper_title: A computational model of trust and reputation

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Despite their many advantages, e-businesses lag behind brick and mortar businesses in several fundamental respects. This paper concerns one of these: relationships based on trust and reputation. Recent studies on simple reputation systems for e-Businesses such as eBay have pointed to the importance of such rating systems for deterring moral hazard and encouraging trusting interactions. However, despite numerous studies on trust and reputation systems, few have taken studies across disciplines to provide an integrated account of these concepts and their relationships. This paper first surveys existing literatures on trust, reputation and a related concept: reciprocity. Based on sociological and biological understandings of these concepts, a computational model is proposed. This model can be implemented in a real system to consistently calculate agents' trust and reputation scores.
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paper_title: AN INTEGRATIVE MODEL OF ORGANIZATIONAL TRUST.

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Scholars in various disciplines have considered the causes, nature, and effects of trust. Prior approaches to studying trust are considered, including characteristics of the trustor, the trustee, and the role of risk. A definition of trust and a model of its antecedents and outcomes are presented, which integrate research from multiple disciplines and differentiate trust from similar constructs. Several research propositions based on the model are presented.
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paper_title: Trust: A Sociological Theory

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Introduction 1. The turn towards soft variables in sociological theory 2. The idea of trust 3. Varieties of trust 4. Foundations of trust 5. The functions of trust 6. The culture of trust 7. Trust in democracy and autocracy 8. Trust and rapid social change: a case study Bibliography References Index.
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paper_title: A Survey of Trust and Reputation Systems for Online Service Provision

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Trust and reputation systems represent a significant trend in decision support for Internet mediated service provision. The basic idea is to let parties rate each other, for example after the completion of a transaction, and use the aggregated ratings about a given party to derive a trust or reputation score, which can assist other parties in deciding whether or not to transact with that party in the future. A natural side effect is that it also provides an incentive for good behaviour, and therefore tends to have a positive effect on market quality. Reputation systems can be called collaborative sanctioning systems to reflect their collaborative nature, and are related to collaborative filtering systems. Reputation systems are already being used in successful commercial online applications. There is also a rapidly growing literature around trust and reputation systems, but unfortunately this activity is not very coherent. The purpose of this article is to give an overview of existing and proposed systems that can be used to derive measures of trust and reputation for Internet transactions, to analyse the current trends and developments in this area, and to propose a research agenda for trust and reputation systems.
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paper_title: Trust : making and breaking cooperative relations

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Part 1 Trust considered: formal structures and social reality, Bernard Williams the biological evolution of co-operation and trust, Patrick Bateson individuals, interpersonal relations and trust, David Good trust as a commodity, Partha Dasgupta trust and political agency, John Dunn familiarity, confidence, trust - problems and alternatives, Niklas Luhmann. Part 2 Trust observed: three ironies in trust, Geoffrey Hawthorn the distraction of trust and its economic consequences in the case of 18th-century Naples, Anthony Pagden trust, cohesion and the social order, Ernest Gellner mafia - the price of distrust, Diego Gambetta kinship, contract and trust - the economic organization of migrants in an African city slum, Keith Hart neither friends nor strangers - informal networks of subcontracting in French industry, Edward Lorenz.
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paper_title: Security and Trust Issues in Semantic Grids

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Grid computing allows sharing of services and resources accross ::: institutions. However, current Grid security mechanisms for authentication ::: and authorization are too rigid and they lack the ability to ::: determine how ``trustworthy'' the result obtained from a specific provider ::: is likely to be. This paper describes the different facets associated to ::: Trust and identifies the need for Trust Management approaches in the ::: context of Virtual Organizations lifecycle and resource access control in ::: the Grid.
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paper_title: A Testbed for Comparing Trust Computation Algorithms

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Trust is the expectation of a person about another person’s behavior. Trust is important for many security related decisions about, e.g., granting or revoking privileges, controlling access to sensitive resources and information, or evaluating intelligence gathered from multiple sources. More often than not, the issue is complicated even further because the person making the decision has no direct trust relationship with every single subject whose trustworthiness needs to be evaluated. So, the decision maker needs to rely on recommendations by others, and then somehow aggregate the trust related information that is collected. In this work we provide an algebraic framework in which we can describe multiple ways that trust related information can be aggregated to form a single value. We show the similarities and differences that the various so called trust computation algorithms have, and associate these with the algebraic properties of the framework that we consider.
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paper_title: Statistical trust establishment in wireless sensor networks

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We present a new distributed approach that establishes reputation-based trust among sensor nodes in order to identify malfunctioning and malicious sensor nodes and minimize their impact on applications. Our method adapts well to the special characteristics of wireless sensor networks, the most important being their resource limitations. Our methodology computes statistical trust and a confidence interval around the trust based on direct and indirect experiences of sensor node behavior. By considering the trust confidence interval, we are able to study the tradeoff between the tightness of the trust confidence interval with the resources used in collecting experiences. Furthermore, our approach allows dynamic scaling of redundancy levels based on the trust relationship between the nodes of a wireless sensor network. Using extensive simulations we demonstrate the benefits of our approach over an approach that uses static redundancy levels in terms of reduced energy consumption and longer life of the network. We also find that high confidence trust can be computed on each node with a relatively small memory overhead and used to determine the level of redundancy operations among nodes in the system.
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paper_title: Valuation of Trust in Open Networks

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Authentication in open networks usually requires participation of trusted entities. Many protocols allow trust to be obtained by recommendation of other entities whose recommendations are known to be reliable. To consider an entity as being trustworthy, especially if there have been several mediators or contradicting recommendations, it is necessary to have a means of estimating its trustworthiness. In this paper we present a method for the valuation of trustworthiness which can be used to accept or reject an entity as being suitable for sensitive tasks. It constitutes an extension of the work of Yahalom, Klein and Beth ([YKB93]).
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paper_title: A fuzzy model for context-dependent reputation

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This paper extends the previous work on constructing reputation axiomatics [28] to define context-dependent reputation (e.g. occupation-specific). In short, to employ theoretic-set approach, both notions of reputation and recommendations are downcasted to the basic notion of responsibility. Notion of "a context" is understood as a synonym of "a universe of discourse."
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paper_title: Trust-enhanced Security in Location-based Adaptive Authentication

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We propose trust to enhance security in adaptive and non-intrusive user authentication in controlled and pervasive environments. In addition to who a user is (e.g., via biometrics) and what a user knows (e.g., a password, a PIN), recent authentication solutions evaluate what a user has. The user's identity is then derived from what detectable accredited items (e.g., badges, RFIDs) and personal devices (e.g., smart-phones, PDAs) the user shows when authenticating. The level of security of the access is set consequently. Position information is also considered in authentication; only those users carrying authorised items in proximity of certain places can benefit from available resources at those places. Unfortunately, items such as badges, mobile phones, smart phones, RFID-ed cards can be stolen, forgotten, or lost with a consequent risk of identity theft and intrusion. In controlled environment like buildings, where sensors can detect a wide range of different types of items, the security of authentication can be improved by evaluating the amount of trust that can be reposed on the user standing in the area from where he tries to access a resource. This piece of information can be calculated from the positions of all the items linkable to the requester as sensed along time by the different sensors available. Sensors are seen as recommenders that give opinions on a user being in a requested position depending on what they have perceived in the environment. We apply Subjective Logics to model recommendations that originate from different types of location detectors and to combine them into a trust value. Our solution has been tested to improve authentication in an intelligent coffee corner of our research institute. A user at the coffee corner can see, displayed on a wall screen, the position of his colleagues depending on the level of authentication he obtains. The user authentication level depends on the number and on the quality of tokens he provides when authenticating. We comment how the use of a location-based trust (on the requester standing at the coffee corner) improves the adaptability, the non-intrusiveness, and the security of the authentication process. We validate our proposal with a simulation that shows how location-based trust changes when a user device moves away from the coffee corner.
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paper_title: The Beta Reputation System

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Reputation systems can be used to foster good behaviour and to encourage adherence to contracts in e-commerce. Several reputation systems have been deployed in practical applications or proposed in the literature. This paper describes a new system called the beta reputation system which is based on using beta probability density functions to combine feedback and derive reputation ratings. The advantage of the beta reputation system is flexibility and simplicity as well as its foundation on the theory of statistics.
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paper_title: A Fuzzy Approach to a Belief-Based Trust Computation

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The approaches to the trust study are various and very different each of other. In our view, just a socio-cognitive approach to trust would be able to analyze the sub-components (the basic beliefs) on which the final decision to trust or not is taken. In this paper we show a first implementation and advance of the socio-cognitive model of trust developed in [1, 2] using the so-called Fuzzy Cognitive Maps. With this implementation we show how the different components may change and how their impact can change depending from the specific situation and from the agent personality.
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paper_title: Modeling and Managing the Trust for Wireless and Mobile Ad Hoc Networks

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With the growing popularity of wireless mobile ad hoc networks (MANETs), many security concerns have arisen from MANETs especially in that misbehaving nodes pose a major threat during the construction of a trusted network. A reputation-based trust system can track the behavior of nodes and thereby proceed by rewarding well-behaving nodes and punishing misbehaving ones. However, existing techniques are usually either energy-consuming or complicated since the relevant reputation information is propagated throughout the network. In this paper, we propose a novel trust computation and management system, called TOMS, which not only establishes the new concepts of trust and community but also includes both the trust computation model and trust management mechanism. Using the results of extensive simulations, we highlight the effectiveness and efficiency of our trust system in comparison to other trust schemes in traditional protocols. Thus, TOMS is shown to be dynamic, distributed, and efficient, as well as sensitive to suspicious behaviors and peers.
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paper_title: Trust evaluation in ad-hoc networks

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An important concept in network security is trust, interpreted as a relation among entities that participate in various protocols. Trust relations are based on evidence related to the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation process of trust evidence in Ad Hoc Networks. Because of the dynamic nature of Ad Hoc Networks, trust evidence may be uncertain and incomplete. Also, no pre-established infrastructure can be assumed. The process is formulated as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. The results are robust in the presence of attackers. We give intuitive requirements for any trust evaluation algorithm. The performance of the scheme is evaluated on three topologies.
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paper_title: Robust cooperative trust establishment for MANETs

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In a mobile ad hoc network (MANET), a source node must rely on intermediate nodes to forward its packets along multi-hop routes to the destination node. Due to the lack of infrastructure in such networks,secure and reliable packet delivery is diffocult to achieve. We propose a robust cooperative trust establishment scheme to improve the reliability of packet delivery in MANETs, particularly in the presence of malicious nodes. In the proposed scheme, each node determines the trustworthiness of the other nodes with respect to reliable packet forwarding by combining first-hand trust information obtained independently of other nodes and second-hand trust information obtained via recommendations from other nodes. First-hand trust information for neighbor nodes is obtained via direct observations at the MAC layer whereas first-hand information for non-neighbor nodes is obtained via feedback from acknowledgements sent in response to data packets. The proposed scheme exploits information sharing among nodes to accelerate the convergence of trust establishment procedures, yet is robust against the propagation of false trust information by malicious nodes. We present simulation results which demonstrate the effectiveness of the proposed scheme in a variety of scenarios involving nodes that are malicious both with respect to packet forwarding and trust propagation.
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paper_title: Using probabilistic argumentation for key validation in public-key cryptography

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The purpose of this paper is to show how probabilistic argumentation is applicable to modern public-key cryptography as an appropriate tool to evaluate webs of trust. This is an interesting application of uncertain reasoning that has not yet received much attention in the corresponding literature.
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paper_title: Computing and Applying Trust in Web-based Social Networks

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The proliferation of web-based social networks has lead to new innovations in social networking, particularly by allowing users to describe their relationships beyond a basic connection. In this dissertation, I look specifically at trust in web-based social networks, how it can be computed, and how it can be used in applications. I begin with a definition of trust and a description of several properties that affect how it is used in algorithms. This is complemented by a survey of web-based social networks to gain an understanding of their scope, the types of relationship information available, and the current state of trust. ::: The computational problem of trust is to determine how much one person in the network should trust another person to whom they are not connected. I present two sets of algorithms for calculating these trust inferences: one for networks with binary trust ratings, and one for continuous ratings. For each rating scheme, the algorithms are built upon the defined notions of trust. Each is then analyzed theoretically and with respect to simulated and actual trust networks to determine how accurately they calculate the opinions of people in the system. I show that in both rating schemes the algorithms presented can be expected to be quite accurate. ::: These calculations are then put to use in two applications. FilmTrust is a website that combines trust, social networks, and movie ratings and reviews. Trust is used to personalize the website for each user, displaying recommended movie ratings, and ordering reviews by relevance. I show that, in the case where the user's opinion is divergent from the average, the trust-based recommended ratings are more accurate than several other common collaborative filtering techniques. The second application is TrustMail, an email client that uses the trust rating of each sender as a score for the message. Users can then sort messages according to their trust value. ::: I conclude with a description of other applications where trust inferences can be used, and how the lessons from this dissertation can be applied to infer information about relationships in other complex systems.
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paper_title: Trust Management in Ad Hoc Network for Secure DSR Routing

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An ad hoc network is wireless, self-configuring network of mobile routers forming a dynamic topology. In such an environment, any malicious behavior by these routers (nodes) could greatly compromise secured routing. However, just detecting the malicious nodes is not enough to guarantee security. It should be ensured that, only trusted nodes take part in routing. In this paper, we propose a distributed dynamic trust evaluation scheme for securing DSR routing in mobile ad hoc and sensor networks. Each node periodically calculates trust for others based on its direct experience, recommendation and previous knowledge. Extensive simulation studies show that our scheme, unlike most of the previously proposed ones, efficiently adapt to fast changing trust scenario and the trust converges to values, revealed by long term behavior of the nodes. This scheme is resistant to ‘ collusion’ attack and is cautious not to punish nodes when packet is dropped due to ‘ node mobility’
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paper_title: Trustworthiness in Networks: A Simulation Approach for Approximating Local Trust and Distrust Values

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Trust is essential for most social and business networks in the web, and determining local trust values between two unfamiliar users is an important issue. However, many existing approaches to calculating these values have limitations in various constellations or network characteristics. We therefore propose an approach that interprets trust as probability and is able to estimate local trust values on large networks using a Monte Carlo simulation method. The estimation is based on existing indirect trust statements between two unfamiliar users. This approach is then extended to the SimTrust algorithm that incorporates both trust and distrust values. It is implemented and discussed in detail with examples. Our main contribution is a new approach which incorporates all available trust and distrust information in such a way that basic trust properties are satisfied.
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paper_title: Statistical trust establishment in wireless sensor networks

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We present a new distributed approach that establishes reputation-based trust among sensor nodes in order to identify malfunctioning and malicious sensor nodes and minimize their impact on applications. Our method adapts well to the special characteristics of wireless sensor networks, the most important being their resource limitations. Our methodology computes statistical trust and a confidence interval around the trust based on direct and indirect experiences of sensor node behavior. By considering the trust confidence interval, we are able to study the tradeoff between the tightness of the trust confidence interval with the resources used in collecting experiences. Furthermore, our approach allows dynamic scaling of redundancy levels based on the trust relationship between the nodes of a wireless sensor network. Using extensive simulations we demonstrate the benefits of our approach over an approach that uses static redundancy levels in terms of reduced energy consumption and longer life of the network. We also find that high confidence trust can be computed on each node with a relatively small memory overhead and used to determine the level of redundancy operations among nodes in the system.
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paper_title: Zone-based trust management in sensor networks

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In this work, we propose a zone-based trust management scheme in wireless sensor networks in order to detect and revoke groups of compromised nodes by region. Our scheme works with less overhead than the existing trust management schemes since multiple compromised nodes in a zone can be detected and revoked at a time. We also present the possible attacks against our scheme and describe the countermeasures of these attacks.
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paper_title: A quantitative trust establishment framework for reliable data packet delivery in MANETs

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In mobile ad hoc networks (MANETs), a source node must rely on other nodes to forward its packets on multi-hop routes to the destination. Secure and reliable handling of packets by the intermediate nodes is difficult to ensure in an ad hoc environment. We propose a trust establishment scheme for MANETs which aims to improve the reliability of packet forwarding over multi-hop routes in the presence of potentially malicious nodes. Each node forms an "opinion" about each of the other nodes based on both first and second-hand observation data collected from the network. The opinion metric can be incorporated into ad hoc routing protocols to achieve reliable packet delivery even when a portion of the network exhibits malicious behavior. We present numerical results which demonstrate the effectiveness of the proposed trust establishment scheme.
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paper_title: Trust Establishment In Pure Ad-hoc Networks

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An ad-hoc network is a set of limited range wireless nodes that function in a cooperative manner so as to increase the overall range of the network. Each node in the network pledges to help its neighbours by passing packets to and fro, in return of a similar assurance from them. All is well if all participating nodes uphold such an altruistic behaviour. However, this is not always the case and often nodes are subjected to a variety of attacks by other nodes. These attacks range from naive passive eavesdropping to vicious battery draining attacks. Routing protocols, data, battery power and bandwidth are the common targets of these attacks. In order to overcome such attacks a number of routing protocols have been devised that use cryptographic algorithms to secure the routing mechanism, which in turn protects the other likely targets. A limiting requirement regarding these protocols is the reliance on an omnipresent, and often omniscient, trust authority. In our opinion, this reliance on a central entity is against the very nature of ad-hoc networks, which are supposed to be improvised and spontaneous. We present in this paper, a trust-based model for communication in ad-hoc networks that is based on individual experience rather than on a third party advocating trust levels. The model introduces the notion of belief and provides a dynamic measure of reliability and trustworthiness in pure ad-hoc networks.
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paper_title: A Robust Reputation System for P2P and Mobile Ad-hoc Networks

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Reputation systems can 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. We propose a fully distributed reputation system that can cope with false disseminated information. In our approach, everyone maintains a reputation rating and a trust rating about everyone else that they care about. From time to time first-hand reputation information is exchanged with others; using a modified Bayesian approach we designed and present in this paper, only second-hand reputation information that is not incompatible with the current reputation rating is accepted. Thus, reputation ratings are slightly modified by accepted information. Trust ratings are updated based on the compatibility of second-hand reputation information with prior reputation ratings. Data is entirely distributed: someone’s reputation and trust is the collection of ratings maintained by others. We enable redemption and prevent the sudden exploitation of good reputation built over time by introducing re-evaluation and reputation fading.
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paper_title: Trust Evaluation in Anarchy: A Case Study on Autonomous Networks

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With the explosive growth of network techniques, in particular wireless communications, the traditional centralized, fixed networks can no longer satisfy the enormous demands on network connectivity, data storage and information exchanges. New types of networks, such as pervasive computing networks, mobile ad hoc networks and P2P networks, emerged in recent years in order to provide solutions for the increasing requirements on networked services. All those networks are autonomous networks, because they are distributed and self-organized. As a case study, we employ a specific application – distributed trust management – to understand and analyze the behavior and properties of these “anarchical” autonomous networks. We propose a statistical trust evaluation rule, prove its convergence and investigate its characteristics when the system is at the steady state. Our investigation results in several conclusions for the design of trust evaluation rules, some of which are unexpected if we do not have the stationary distribution at hand. Our study shows the importance and necessity of applying theoretical analyses to understand the complex characteristics of distributed, self-organized, autonomous networks.
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paper_title: A dynamic trust model for mobile ad hoc networks

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This paper introduces a trust model for mobile ad hoc networks. Initially each node is assigned a trust level. Then we use several approaches to dynamically update trust levels by using reports from threat detection tools, such as intrusion detection systems (IDS), located on all nodes in the network. The nodes neighboring to a node exhibiting suspicious behavior initiate trust reports. These trust reports are propagated through the network using one of our proposed methods. A source node can use the trust levels it establishes for other nodes to evaluate the security of routes to destination nodes. Using these trust levels as a guide, the source node can then select a route that meets the security requirements of the message to be transmitted. This paper demonstrates important concepts for establishing a collaborative, dynamic trust model and for using this model as an example to enhance the security of message routing in mobile ad hoc networks.
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paper_title: On trust models and trust evaluation metrics for ad hoc networks

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Within the realm of network security, we interpret the concept of trust as a relation among entities that participate in various protocols. Trust relations are based on evidence created by the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation of trust evidence in ad hoc networks. Because of the dynamic nature of ad hoc networks, trust evidence may be uncertain and incomplete. Also, no preestablished infrastructure can be assumed. The evaluation process is modeled as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We give intuitive requirements and discuss design issues for any trust evaluation algorithm. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. We show that our semiring framework is flexible enough to express other trust models, most notably PGP's Web of Trust. Our scheme is shown to be robust in the presence of attackers.
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paper_title: An adaptive probabilistic trust model and its evaluation

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In open settings, the participants are autonomous and there is no central authority to ensure the felicity of their interactions. When agents interact in such settings, each relies upon being able to model the trustworthiness of the agents with whom it interacts. Fundamentally, such models must consider the past behavior of the other parties in order to predict their future behavior. Further, it is sensible for the agents to share information via referrals to trustworthy agents. Much progress has recently been made on probabilistic trust models including those that support the aggregation of information from multiple sources. However, current models do not support trust updates, leaving updates to be handled in an ad hoc manner. ::: ::: This paper proposes a trust representation that combines probabilities and certainty (defined as a function of a probability-certainty density function). Further, it offers a trust update mechanism to estimate the trustworthiness of referrers. This paper describes a testbed that goes beyond existing testbeds to enable the evaluation of a composite probability-certainty model. It then evaluates the proposed trust model showing that the trust model can (a) estimate trustworthiness of damping and capricious agents correctly, (b) update trust values of referrers accurately, and (c) resolve the conflicts in referral networks by certainty discounting.
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paper_title: Trust and Recommendations in Mobile Ad hoc Networks

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Recently several trust and reputation models have been proposed to enhance the security of mobile ad hoc networks. In these models, recommendations are circulated by forwarding explicit messages or introducing extra message headers. Apart from incurring additional overhead, the recommendations are prone to issues such as recommender's bias, honest-elicitation, and free-riding. In this paper, we propose a trust model to enhance the security of mobile ad hoc networks and to address the issues related to recommendations. The model uses only trusted routes for communication, and isolates malicious nodes depending on the evidence collected from direct interactions and recommendations. It deploys a novel approach for communicating recommendations such that they are free from recommender's bias, honest-elicitation, and free-riding. Simulation results confirm the effectiveness of our model.
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paper_title: Formal Trust Model for Multiagent Systems

paper_content:

Trust should be substantially based on evidence. Further, a key challenge for multiagent systems is how to determine trust based on reports from multiple sources, who might themselves be trusted to varying degrees. Hence an ability to combine evidence-based trust reports in a manner that discounts for imperfect trust in the reporting agents is crucial for multiagent systems. ::: ::: This paper understands trust in terms of belief and certainty: A's trust in B is reflected in the strength of A's belief that B is trustworthy. This paper formulates certainty in terms of evidence based on a statistical measure defined over a probability distribution of the probability of positive outcomes. This novel definition supports important mathematical properties, including (1) certainty increases as conflict increases provided the amount of evidence is unchanged, and (2) certainty increases as the amount of evidence increases provided conflict is unchanged. Moreover, despite a more subtle definition than previous approaches, this paper (3) establishes a bijection between evidence and trust spaces, enabling robust combination of trust reports and (4) provides an efficient algorithm for computing this bijection.
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paper_title: Trust overlay networks for global reputation aggregation in P2P grid computing

paper_content:

This paper presents a new approach to trusted grid computing in a peer-to-peer (P2P) setting. Trust and security are essential to establish lasting working relationships among the peers. A P2P reputation system collects peer trust scores and aggregates them to yield a global reputation. We use a new trust overlay network (TON) to model the trust relationships among the peers. After analyzing the eBay transaction trace data, we discover a power-law distribution in user feedbacks. We develop a new reputation system, PowerTrust, to leverage power-law feedback characteristics. The PowerTrust system is built with locality-preserving hash functions and a lookahead random walk strategy. Dynamic system reconfiguration is enabled by the use of power nodes with well-established reputations. Through P2P simulation experiments on distributed file sharing and grid parameter-sweeping applications (PSA), we demonstrate the PowerTrust advantages in fast reputation convergence and accurate ranking of peer reputations. We report performance results with enhanced P2P query success rate, shortened job makespan, and increased job success rate in scalable P2P grid applications.
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paper_title: Information theoretic framework of trust modeling and evaluation for ad hoc networks

paper_content:

The performance of ad hoc networks depends on cooperation and trust among distributed nodes. To enhance security in ad hoc networks, it is important to evaluate trustworthiness of other nodes without centralized authorities. In this paper, we present an information theoretic framework to quantitatively measure trust and model trust propagation in ad hoc networks. In the proposed framework, trust is a measure of uncertainty with its value represented by entropy. We develop four Axioms that address the basic understanding of trust and the rules for trust propagation. Based on these axioms, we present two trust models: entropy-based model and probability-based model, which satisfy all the axioms. Techniques of trust establishment and trust update are presented to obtain trust values from observation. The proposed trust evaluation method and trust models are employed in ad hoc networks for secure ad hoc routing and malicious node detection. A distributed scheme is designed to acquire, maintain, and update trust records associated with the behaviors of nodes' forwarding packets and the behaviors of making recommendations about other nodes. Simulations show that the proposed trust evaluation system can significantly improve the network throughput as well as effectively detect malicious behaviors in ad hoc networks.
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paper_title: Enhanced Reputation Mechanism for Mobile Ad Hoc Networks

paper_content:

Interactions between entities unknown to each other are inevitable in the ambient intelligence vision of service access anytime, anywhere. Trust management through a reputation mechanism to facilitate such interactions is recognized as a vital part of mobile ad hoc networks, which features lack of infrastructure, autonomy, mobility and resource scarcity of composing light-weight terminals. However, the design of a reputation mechanism is faced by challenges of how to enforce reputation information sharing and honest recommendation elicitation. In this paper, we present a reputation model, which incorporates two essential dimensions, time and context, along with mechanisms supporting reputation formation, evolution and propagation. By introducing the notion of recommendation reputation, our reputation mechanism shows effectiveness in distinguishing truth-telling and lying agents, obtaining true reputation of an agent, and ensuring reliability against attacks of defame and collusion.
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paper_title: Trust management in mobile ad hoc networks using a scalable maturity-based model

paper_content:

In this paper, we propose a human-based model which builds a trust relationship between nodes in an ad hoc network. The trust is based on previous individual experiences and on the recommendations of others. We present the Recommendation Exchange Protocol (REP) which allows nodes to exchange recommendations about their neighbors. Our proposal does not require disseminating the trust information over the entire network. Instead, nodes only need to keep and exchange trust information about nodes within the radio range. Without the need for a global trust knowledge, our proposal scales well for large networks while still reducing the number of exchanged messages and therefore the energy consumption. In addition, we mitigate the effect of colluding attacks composed of liars in the network. A key concept we introduce is the relationship maturity, which allows nodes to improve the efficiency of the proposed model for mobile scenarios. We show the correctness of our model in a single-hop network through simulations. We also extend the analysis to mobile multihop networks, showing the benefits of the maturity relationship concept. We evaluate the impact of malicious nodes that send false recommendations to degrade the efficiency of the trust model. At last, we analyze the performance of the REP protocol and show its scalability. We show that our implementation of REP can significantly reduce the number messages.
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paper_title: Quantifying trust in mobile ad-hoc networks

paper_content:

This paper introduces a trust-domain based security architecture for mobile ad-hoc networks (MANETs). The aim of this architecture is twofold: to use trust as a basis to establish keys between nodes in a MANET, and to utilize trust as a metric for establishing secure distributed control in infrastructure-less MANETs. We define metrics for nodes to establish and manage trust, and use this mutual trust to make decisions on establishing group and pair-wise keys in the network. The impact of mobility of the nodes on trust establishment is considered and further its use as a means of propagating trust through the network is investigated. We introduce the concept of self-organizing trust-based physical-logical domains (PLDs) as a means of grouping nodes for distributed control in the network.
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paper_title: Markov Chain Trust Model for Trust-Value Analysis and Key Management in Distributed Multicast MANETs

paper_content:

To increase efficiency in mobile ad hoc networks (MANETs), the multicast MANET is proposed for a sender that sends packets to several receivers through a multicast session. In MANETs, multicast group members frequently change due to node mobility; thus, supporting secure authentication and authorization in a multicast MANET is more critical than that in a wired network with a centralized certificate authentication (CA) server. This paper thus proposes a two-step secure authentication approach for multicast MANETs. First, a Markov chain trust model is proposed to determine the trust value (TV) for each one-hop neighbor. A node's TV is analyzed from its previous trust manner that was performed in this group. The proposed trust model is proven as an ergodic continuous-time Markov chain model. Second, the node with the highest TV in a group will be selected as the CA server. To increase reliability, the node with the second highest TV will be selected as the backup CA server that will take over CA when CA fails. The procedures of the secure authentication for group management are detailed. The security analysis of each procedure is analyzed to guarantee that the proposed approach achieves a secure reliable authentication in multicast MANETs. In addition, several famous attacks have been analyzed and discussed. Numerical results indicate that the analytical TV of each mobile node is very close to that of simulation under various situations. The speed of the convergence of the analytical TV shows that the analyzed result is independent of initial values and trust classes. This is a good feature of analytical models.
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paper_title: A Distributed Trust Model for Securing Mobile Ad Hoc Networks

paper_content:

In mobile ad hoc networks, the security enforcement and its implementation becoming increasingly difficult due to quasi-static nature of the mobile nodes (wireless communication devices), no fixed network topology and more importantly absence of centralized authority. In such networks, communication links between nodes may be bandwidth constrained, messages typically roamed in multi-hoped fashion, nodes may be powered by limited energy source and also have limited physical security. The major challenge in such networks is to give a robust security solution. The complexity of the problem is compounded by the fact that both active and passive attackers may present in the system, and nodes may not function properly in order to save its own energy by selective forwarding of the packets. This paper presents a distributed trust based security framework for ad hoc networks. We have proposed a clustering mechanism and security is enforced by local monitoring system by a new kind of nodes referred as guard nodes. This framework stems from cryptographic computation, which is not suitable in this scenario. The trust is computed depending upon some parameters which have a primary role in enforcing security and cooperation between the nodes. Also this solution conforms graceful leave and dynamic secure allocation of IP of the nodes.
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paper_title: Algorithms for dempster-shafer theory

paper_content:

The method of reasoning with uncertain information known as Dempster-Shafer theory arose from the reinterpretation and development of work of Arthur Dempster [Dempster, 1967; 1968] by Glenn Shafer in his book a mathematical theory of evidence [Shafer, 1976], and further publications e.g., [Shafer, 1981; 1990]. More recent variants of Dempster-Shafer theory include the Transferable Belief Model see e.g., [Smets, 1988; Smets and Keimes, 1994] and the Theory of Hints e.g., [Kohlas and Monney, 1995].
---
paper_title: A trust evaluation framework in distributed networks: Vulnerability analysis and defense against attacks

paper_content:

The performance of distributed networks depends on collaboration among distributed entities. To enhance security in distributed networks, such as ad hoc networks, it is important to evaluate the trustworthiness of participating entities since trust is the major driving force for collaboration. In this paper, we present a framework to quantitatively measure trust, model trust propagation, and defend trust evaluation systems against malicious attacks. In particular, we address the fundamental understanding of trust, quantitative trust metrics, mathematical properties of trust, dynamic properties of trust, and trust models. The attacks against trust evaluation are identified and defense techniques are developed. The proposed trust evaluation system is employed in ad hoc networks for securing ad hoc routing and assisting malicious node detection. The implementation is fully distributed. Simulations show that the proposed system can significantly improve network throughput as well as effectively detect malicious behaviors in ad hoc networks. Further, extensive simulations are performed to illustrate various attacks and the effectiveness of the proposed defense techniques.
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paper_title: An evidential model of distributed reputation management

paper_content:

For agents to function effectively in large and open networks, they must ensure that their correspondents, i.e., the agents they interact with, are trustworthy. Since no central authorities may exist, the only way agents can find trustworthy correspondents is by collaborating with others to identify those whose past behavior has been untrustworthy. In other words, finding trustworthy correspondents reduces to the problem of distributed reputation management.Our approach adapts the mathematical theory of evidence to represent and propagate the ratings that agents give to their correspondents. When evaluating the trustworthiness of a correspondent, an agent combines its local evidence (based on direct prior interactions with the correspondent) with the testimonies of other agents regarding the same correspondent. We experimentally studied this approach to establish that some important properties of trust are captured by it.
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paper_title: Trust Management Problem in Distributed Wireless Sensor Networks

paper_content:

Sensor network security solutions that have been proposed so far are mostly built on the assumption of a trusted environment, which is not very realistic so we need trust management before deploying any other security solution. Traditional trust management schemes that have been developed for wired and wireless ad-hoc networks are not suitable for wireless sensor networks because of higher consumption of resources such as memory and power. In this paper, we propose a novel lightweight group based trust management scheme (GTMS) for distributed wireless sensor networks in which the whole group will get a single trust value. Instead of using completely centralized or distributed trust management schemes, GTMS uses hybrid trust management approach that helps in keeping minimum resource utilization at the sensor nodes.
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paper_title: A security management scheme using a novel computational reputation model for wireless and mobile ad hoc networks

paper_content:

Robust trust and reputation evaluation services are significant to ensure the security of mobile ad hoc networks, as centralized administration is not easy to be applied and these networks do not have fixed infrastructures. However, malicious behaviors obviously can make wireless and mobile networks at risk so malicious nodes should be detected and excluded. In this paper, we study the issue of how to evaluate efficiently a node's reputation in a distributed approach. First, a set of management mechanisms is presented to prevent effectively malicious nodes from entering the trusted community. Then we formulate a comprehensive computational reputation model. Through a set of extensive simulation experiments based on the ns-2 simulator, our simulation results demonstrate that our system indeed are more sensitive to suspicious behaviors and peers, and thereby improper behaviors within a community are prevented effectively. Therefore, in dynamic but agile environments, our computational reputation system exhibits high adaptation and low complexity, so that it leads to secure communication among mobile nodes.
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paper_title: Provenance-Based Information Trustworthiness Evaluation in Multi-Hop Networks

paper_content:

In this paper, we present a trust model to evaluate the trustworthiness of information as well as the information publishing nodes based on the information provenance. We consider two factors in evaluating the provenance-based information trust: Path Similarity and Information Similarity. In multihop networks, information can flow through multiple hops from multiple paths. We model the similarity between different paths which deliver information about the same event and the similarity between two information items about the same event which are delivered through different paths. Both path and information similarity factors are considered in determining the trust of the information. This information trust is indeed used as a feedback factor to adaptively adjust trust of the nodes in the network. Detailed analysis of the proposed approach is presented along with simulation results for validation.
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paper_title: Modeling and Managing the Trust for Wireless and Mobile Ad Hoc Networks

paper_content:

With the growing popularity of wireless mobile ad hoc networks (MANETs), many security concerns have arisen from MANETs especially in that misbehaving nodes pose a major threat during the construction of a trusted network. A reputation-based trust system can track the behavior of nodes and thereby proceed by rewarding well-behaving nodes and punishing misbehaving ones. However, existing techniques are usually either energy-consuming or complicated since the relevant reputation information is propagated throughout the network. In this paper, we propose a novel trust computation and management system, called TOMS, which not only establishes the new concepts of trust and community but also includes both the trust computation model and trust management mechanism. Using the results of extensive simulations, we highlight the effectiveness and efficiency of our trust system in comparison to other trust schemes in traditional protocols. Thus, TOMS is shown to be dynamic, distributed, and efficient, as well as sensitive to suspicious behaviors and peers.
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paper_title: Cluster-Based Trust Model against Attacks in Ad-Hoc Networks

paper_content:

In ad-hoc environments, all nodes have function to set themselves a route and build a network. It is important how trustable each node is in the environment. This study proposes the cluster-based trust model, and uses the model to discuss how you can solve some possible problems occurred in the network. The reputation from a neighboring node is applied to the calculation of the trust value. If the trust value of a truster is used as a weight, more sophisticated calculation of the trust value is available. When you create a cluster, all nodes in the cluster can fully trust the selected head, if entire nodes in the cluster participate in the head competition. And then, the head node issues the certificate that shows the trust level of each member node. If a node moves from one cluster to another, the trust level of the node is determined by the certificate issued by the previous cluster-head. The model proposed by this study can monitor the selfish behavior of nodes in the network and isolate the selfish nodes from the network to enhance the effectiveness throughout the network.
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paper_title: DTT: A Distributed Trust Toolkit for pervasive systems

paper_content:

Effective security mechanisms are essential to the widespread deployment of pervasive systems. Much of the research focus on security in pervasive computing has revolved around distributed trust management. While such mechanisms are effective in specific environments, there is no generic framework for deploying and extending these mechanisms over a variety of pervasive systems. We present the design and implementation of a novel framework called Distributed Trust Toolkit (DTT), for implementing and evaluating trust mechanisms in pervasive systems. The DTT facilitates the extension and adaptation of trust mechanisms by abstracting trust mechanisms into interchangeable components. Furthermore, the DTT provides a set of tools and interfaces to ease implementation of trust mechanisms and facilitate their execution on a variety of platforms and networks. In addition to the adaptability and extensibility provided by this design, we demonstrate through simulation that use of DTT improves utilization of resources and enhances performance of existing trust mechanisms in pervasive systems. We are currently developing an implementation of the DTT that can be easily deployed in pervasive environments.
---
paper_title: Algorithms for dempster-shafer theory

paper_content:

The method of reasoning with uncertain information known as Dempster-Shafer theory arose from the reinterpretation and development of work of Arthur Dempster [Dempster, 1967; 1968] by Glenn Shafer in his book a mathematical theory of evidence [Shafer, 1976], and further publications e.g., [Shafer, 1981; 1990]. More recent variants of Dempster-Shafer theory include the Transferable Belief Model see e.g., [Smets, 1988; Smets and Keimes, 1994] and the Theory of Hints e.g., [Kohlas and Monney, 1995].
---
paper_title: Statistical trust establishment in wireless sensor networks

paper_content:

We present a new distributed approach that establishes reputation-based trust among sensor nodes in order to identify malfunctioning and malicious sensor nodes and minimize their impact on applications. Our method adapts well to the special characteristics of wireless sensor networks, the most important being their resource limitations. Our methodology computes statistical trust and a confidence interval around the trust based on direct and indirect experiences of sensor node behavior. By considering the trust confidence interval, we are able to study the tradeoff between the tightness of the trust confidence interval with the resources used in collecting experiences. Furthermore, our approach allows dynamic scaling of redundancy levels based on the trust relationship between the nodes of a wireless sensor network. Using extensive simulations we demonstrate the benefits of our approach over an approach that uses static redundancy levels in terms of reduced energy consumption and longer life of the network. We also find that high confidence trust can be computed on each node with a relatively small memory overhead and used to determine the level of redundancy operations among nodes in the system.
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paper_title: Denial of Service Attacks and Defenses in Decentralized Trust Management

paper_content:

Trust management is an approach to scalable and flexible access control in decentralized systems. In trust management, a server often needs to evaluate a chain of credentials submitted by a client; this requires the server to perform multiple expensive digital signature verifications. In this paper, we study low-bandwidth Denial-of-Service (DoS) attacks that exploit the existence of trust management systems to deplete server resources. Although the threat of DoS attacks has been studied for some application-level protocols such as authentication protocols, we show that it is especially destructive for trust management systems. Exploiting the delegation feature in trust management languages, an attacker can forge a long credential chain to force a server to consume a large amount of computing resource. Using game theory as an analytic tool, we demonstrate that unprotected trust management servers will easily fall prey to a witty attacker who moves smartly. We report our empirical study of existing trust management systems, which manifests the gravity of this threat. We also propose a defense technique using credential caching, and show that it is effective in the presence of intelligent attackers.
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paper_title: A Study of On-Off Attack Models for Wireless Ad Hoc Networks

paper_content:

The security of mobile wireless ad hoc networks is a multifaceted topic which in recent years has been the focus of much interest in the research community. While many security issues in these networks can be addressed by protocol design, wireless nodes have inherent physical vulnerabilities that can be exploited by attackers to cause disruptions in network traffic. The nature of these exposures is such that there is little that can be done to eliminate them leaving the network open to denial of service and reduction of quality attacks. It is essential that the impact of such attacks is well-understood before wireless ad hoc networks are used in mission-critical applications. This paper is a step in this risk analysis as our experiments quantify the effects of attacks that exploit physical vulnerabilities. Our contributions in this paper are two fold. First, we introduce a general model that can be used to characterize a physical attack as an on-off process and then we apply this model to two specific attack scenarios. Second, we present the results of a simulation study with these two attack scenarios in the context of a mesh of network nodes using the IEEE 802.11 standard and the AODV routing protocol
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paper_title: Attacks on Trust Evaluation in Distributed Networks

paper_content:

Evaluation of trustworthiness of participating entities is an effective method to stimulate collaboration and improve network security in distributed networks. Similar to other security related protocols, trust evaluation is an attractive target for adversaries. Currently, the vulnerabilities of trust evaluation system have not been well understood. In this paper, we present several attacks that can undermine the accuracy of trust evaluation, and then develop defense techniques. Based on our investigation on attacks and defense, we implement a trust evaluation system in ad hoc networks for securing ad hoc routing and assisting malicious node detection. Extensive simulations are performed to illustrate various attacks, the effectiveness of the proposed defense techniques, and the overall performance of the trust evaluation system.
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paper_title: Mechanisms for coping with unfair ratings and discriminatory behavior in online reputation reporting systems

paper_content:

Reputation reporting systems have emerged as an important risk management mechanism in online trading communities. However, the predictive value of these systems can be compromised in situations where conspiring buyers intentionally give unfair ratings to sellers or where sellers discriminate on the quality of service they provide to different buyers. This paper proposes a set of mechanisms that eliminate or significantly reduce the negative effects of such fraudulent behavior. The proposed mechanisms can be easily integrated into existing online reputation systems in order to safeguard their reliability in the presence of deceitful buyers and sellers.
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paper_title: Trust Models in Wireless Sensor Networks: A Survey

paper_content:

This paper introduces the security and trust concepts in wireless sensor networks and explains the difference between them, stating that even though both terms are used interchangeably when defining a secure system, they are not the same. The difference between reputation and trust is also explained, highlighting that reputation partially affects trust. The methodologies used to model trust and their references are presented. The factors affecting trust updating are summarised and some examples of the systems in which these factors have been implemented are given. The survey states that, even though researchers have started to explore the issue of trust in wireless sensor networks, they are still examining the trust associated with routing messages between nodes (binary events). However, wireless sensor networks are mainly deployed to monitor events and report data, both continuous and discrete. This leads to the development of new trust models addressing the continuous data issue and also to combine the data trust and the communication trust to infer the total trust.
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paper_title: The Sybil Attack

paper_content:

Large-scale peer-to-peer systems face security threats from faulty or hostile remote computing elements. To resist these threats, many such systems employ redundancy. However, if a single faulty entity can present multiple identities, it can control a substantial fraction of the system, thereby undermining this redundancy. One approach to preventing these "Sybil attacks" is to have a trusted agency certify identities. This paper shows that, without a logically centralized authority, Sybil attacks are always possible except under extreme and unrealistic assumptions of resource parity and coordination among entities.
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paper_title: DSybil: Optimal Sybil-Resistance for Recommendation Systems

paper_content:

Recommendation systems can be attacked in various ways, and the ultimate attack form is reached with a {\em sybil attack}, where the attacker creates a potentially unlimited number of {\em sybil identities} to vote. Defending against sybil attacks is often quite challenging, and the nature of recommendation systems makes it even harder. This paper presents {\em DSybil}, a novel defense for diminishing the influence of sybil identities in recommendation systems. DSybil provides strong provable guarantees that hold even under the worst-case attack and are optimal. DSybil can defend against an unlimited number of sybil identities over time. DSybil achieves its strong guarantees by i) exploiting the heavy-tail distribution of the typical voting behavior of the honest identities, and ii) carefully identifying whether the system is already getting ``enough help'' from the (weighted) voters already taken into account or whether more ``help'' is needed. Our evaluation shows that DSybil would continue to provide high-quality recommendations even when a million-node botnet uses an optimal strategy to launch a sybil attack.
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paper_title: The sybil attack in sensor networks: analysis & defenses

paper_content:

Security is important for many sensor network applications. A particularly harmful attack against sensor and ad hoc networks is known as the Sybil attack based on J.R. Douceur (2002), where a node illegitimately claims multiple identities. This paper systematically analyzes the threat posed by the Sybil attack to wireless sensor networks. We demonstrate that the attack can be exceedingly detrimental to many important functions of the sensor network such as routing, resource allocation, misbehavior detection, etc. We establish a classification of different types of the Sybil attack, which enables us to better understand the threats posed by each type, and better design countermeasures against each type. We then propose several novel techniques to defend against the Sybil attack, and analyze their effectiveness quantitatively.
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paper_title: Trust management systems for wireless sensor networks: Best practices

paper_content:

Wireless sensor networks (WSNs) have been proven a useful technology for perceiving information about the physical world and as a consequence has been used in many applications such as measurement of temperature, radiation, flow of liquids, etc. The nature of this kind of technology, and also their vulnerabilities to attacks make the security tools required for them to be considered in a special way. The decision making in a WSN is essential for carrying out certain tasks as it aids sensors establish collaborations. In order to assist this process, trust management systems could play a relevant role. In this paper, we list the best practices that we consider are essential for developing a good trust management system for WSN and make an analysis of the state of the art related to these practices.
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paper_title: Statistical trust establishment in wireless sensor networks

paper_content:

We present a new distributed approach that establishes reputation-based trust among sensor nodes in order to identify malfunctioning and malicious sensor nodes and minimize their impact on applications. Our method adapts well to the special characteristics of wireless sensor networks, the most important being their resource limitations. Our methodology computes statistical trust and a confidence interval around the trust based on direct and indirect experiences of sensor node behavior. By considering the trust confidence interval, we are able to study the tradeoff between the tightness of the trust confidence interval with the resources used in collecting experiences. Furthermore, our approach allows dynamic scaling of redundancy levels based on the trust relationship between the nodes of a wireless sensor network. Using extensive simulations we demonstrate the benefits of our approach over an approach that uses static redundancy levels in terms of reduced energy consumption and longer life of the network. We also find that high confidence trust can be computed on each node with a relatively small memory overhead and used to determine the level of redundancy operations among nodes in the system.
---
paper_title: Trust Management Problem in Distributed Wireless Sensor Networks

paper_content:

Sensor network security solutions that have been proposed so far are mostly built on the assumption of a trusted environment, which is not very realistic so we need trust management before deploying any other security solution. Traditional trust management schemes that have been developed for wired and wireless ad-hoc networks are not suitable for wireless sensor networks because of higher consumption of resources such as memory and power. In this paper, we propose a novel lightweight group based trust management scheme (GTMS) for distributed wireless sensor networks in which the whole group will get a single trust value. Instead of using completely centralized or distributed trust management schemes, GTMS uses hybrid trust management approach that helps in keeping minimum resource utilization at the sensor nodes.
---
paper_title: Trust Evaluation in Anarchy: A Case Study on Autonomous Networks

paper_content:

With the explosive growth of network techniques, in particular wireless communications, the traditional centralized, fixed networks can no longer satisfy the enormous demands on network connectivity, data storage and information exchanges. New types of networks, such as pervasive computing networks, mobile ad hoc networks and P2P networks, emerged in recent years in order to provide solutions for the increasing requirements on networked services. All those networks are autonomous networks, because they are distributed and self-organized. As a case study, we employ a specific application – distributed trust management – to understand and analyze the behavior and properties of these “anarchical” autonomous networks. We propose a statistical trust evaluation rule, prove its convergence and investigate its characteristics when the system is at the steady state. Our investigation results in several conclusions for the design of trust evaluation rules, some of which are unexpected if we do not have the stationary distribution at hand. Our study shows the importance and necessity of applying theoretical analyses to understand the complex characteristics of distributed, self-organized, autonomous networks.
---
paper_title: A security management scheme using a novel computational reputation model for wireless and mobile ad hoc networks

paper_content:

Robust trust and reputation evaluation services are significant to ensure the security of mobile ad hoc networks, as centralized administration is not easy to be applied and these networks do not have fixed infrastructures. However, malicious behaviors obviously can make wireless and mobile networks at risk so malicious nodes should be detected and excluded. In this paper, we study the issue of how to evaluate efficiently a node's reputation in a distributed approach. First, a set of management mechanisms is presented to prevent effectively malicious nodes from entering the trusted community. Then we formulate a comprehensive computational reputation model. Through a set of extensive simulation experiments based on the ns-2 simulator, our simulation results demonstrate that our system indeed are more sensitive to suspicious behaviors and peers, and thereby improper behaviors within a community are prevented effectively. Therefore, in dynamic but agile environments, our computational reputation system exhibits high adaptation and low complexity, so that it leads to secure communication among mobile nodes.
---
paper_title: Formal Trust Model for Multiagent Systems

paper_content:

Trust should be substantially based on evidence. Further, a key challenge for multiagent systems is how to determine trust based on reports from multiple sources, who might themselves be trusted to varying degrees. Hence an ability to combine evidence-based trust reports in a manner that discounts for imperfect trust in the reporting agents is crucial for multiagent systems. ::: ::: This paper understands trust in terms of belief and certainty: A's trust in B is reflected in the strength of A's belief that B is trustworthy. This paper formulates certainty in terms of evidence based on a statistical measure defined over a probability distribution of the probability of positive outcomes. This novel definition supports important mathematical properties, including (1) certainty increases as conflict increases provided the amount of evidence is unchanged, and (2) certainty increases as the amount of evidence increases provided conflict is unchanged. Moreover, despite a more subtle definition than previous approaches, this paper (3) establishes a bijection between evidence and trust spaces, enabling robust combination of trust reports and (4) provides an efficient algorithm for computing this bijection.
---
paper_title: Attacks on Trust Evaluation in Distributed Networks

paper_content:

Evaluation of trustworthiness of participating entities is an effective method to stimulate collaboration and improve network security in distributed networks. Similar to other security related protocols, trust evaluation is an attractive target for adversaries. Currently, the vulnerabilities of trust evaluation system have not been well understood. In this paper, we present several attacks that can undermine the accuracy of trust evaluation, and then develop defense techniques. Based on our investigation on attacks and defense, we implement a trust evaluation system in ad hoc networks for securing ad hoc routing and assisting malicious node detection. Extensive simulations are performed to illustrate various attacks, the effectiveness of the proposed defense techniques, and the overall performance of the trust evaluation system.
---
paper_title: Trust overlay networks for global reputation aggregation in P2P grid computing

paper_content:

This paper presents a new approach to trusted grid computing in a peer-to-peer (P2P) setting. Trust and security are essential to establish lasting working relationships among the peers. A P2P reputation system collects peer trust scores and aggregates them to yield a global reputation. We use a new trust overlay network (TON) to model the trust relationships among the peers. After analyzing the eBay transaction trace data, we discover a power-law distribution in user feedbacks. We develop a new reputation system, PowerTrust, to leverage power-law feedback characteristics. The PowerTrust system is built with locality-preserving hash functions and a lookahead random walk strategy. Dynamic system reconfiguration is enabled by the use of power nodes with well-established reputations. Through P2P simulation experiments on distributed file sharing and grid parameter-sweeping applications (PSA), we demonstrate the PowerTrust advantages in fast reputation convergence and accurate ranking of peer reputations. We report performance results with enhanced P2P query success rate, shortened job makespan, and increased job success rate in scalable P2P grid applications.
---
paper_title: Information theoretic framework of trust modeling and evaluation for ad hoc networks

paper_content:

The performance of ad hoc networks depends on cooperation and trust among distributed nodes. To enhance security in ad hoc networks, it is important to evaluate trustworthiness of other nodes without centralized authorities. In this paper, we present an information theoretic framework to quantitatively measure trust and model trust propagation in ad hoc networks. In the proposed framework, trust is a measure of uncertainty with its value represented by entropy. We develop four Axioms that address the basic understanding of trust and the rules for trust propagation. Based on these axioms, we present two trust models: entropy-based model and probability-based model, which satisfy all the axioms. Techniques of trust establishment and trust update are presented to obtain trust values from observation. The proposed trust evaluation method and trust models are employed in ad hoc networks for secure ad hoc routing and malicious node detection. A distributed scheme is designed to acquire, maintain, and update trust records associated with the behaviors of nodes' forwarding packets and the behaviors of making recommendations about other nodes. Simulations show that the proposed trust evaluation system can significantly improve the network throughput as well as effectively detect malicious behaviors in ad hoc networks.
---
paper_title: Enhanced Reputation Mechanism for Mobile Ad Hoc Networks

paper_content:

Interactions between entities unknown to each other are inevitable in the ambient intelligence vision of service access anytime, anywhere. Trust management through a reputation mechanism to facilitate such interactions is recognized as a vital part of mobile ad hoc networks, which features lack of infrastructure, autonomy, mobility and resource scarcity of composing light-weight terminals. However, the design of a reputation mechanism is faced by challenges of how to enforce reputation information sharing and honest recommendation elicitation. In this paper, we present a reputation model, which incorporates two essential dimensions, time and context, along with mechanisms supporting reputation formation, evolution and propagation. By introducing the notion of recommendation reputation, our reputation mechanism shows effectiveness in distinguishing truth-telling and lying agents, obtaining true reputation of an agent, and ensuring reliability against attacks of defame and collusion.
---
paper_title: Trust management in mobile ad hoc networks using a scalable maturity-based model

paper_content:

In this paper, we propose a human-based model which builds a trust relationship between nodes in an ad hoc network. The trust is based on previous individual experiences and on the recommendations of others. We present the Recommendation Exchange Protocol (REP) which allows nodes to exchange recommendations about their neighbors. Our proposal does not require disseminating the trust information over the entire network. Instead, nodes only need to keep and exchange trust information about nodes within the radio range. Without the need for a global trust knowledge, our proposal scales well for large networks while still reducing the number of exchanged messages and therefore the energy consumption. In addition, we mitigate the effect of colluding attacks composed of liars in the network. A key concept we introduce is the relationship maturity, which allows nodes to improve the efficiency of the proposed model for mobile scenarios. We show the correctness of our model in a single-hop network through simulations. We also extend the analysis to mobile multihop networks, showing the benefits of the maturity relationship concept. We evaluate the impact of malicious nodes that send false recommendations to degrade the efficiency of the trust model. At last, we analyze the performance of the REP protocol and show its scalability. We show that our implementation of REP can significantly reduce the number messages.
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paper_title: Trust Management in Ad Hoc Network for Secure DSR Routing

paper_content:

An ad hoc network is wireless, self-configuring network of mobile routers forming a dynamic topology. In such an environment, any malicious behavior by these routers (nodes) could greatly compromise secured routing. However, just detecting the malicious nodes is not enough to guarantee security. It should be ensured that, only trusted nodes take part in routing. In this paper, we propose a distributed dynamic trust evaluation scheme for securing DSR routing in mobile ad hoc and sensor networks. Each node periodically calculates trust for others based on its direct experience, recommendation and previous knowledge. Extensive simulation studies show that our scheme, unlike most of the previously proposed ones, efficiently adapt to fast changing trust scenario and the trust converges to values, revealed by long term behavior of the nodes. This scheme is resistant to ‘ collusion’ attack and is cautious not to punish nodes when packet is dropped due to ‘ node mobility’
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paper_title: Zone-based trust management in sensor networks

paper_content:

In this work, we propose a zone-based trust management scheme in wireless sensor networks in order to detect and revoke groups of compromised nodes by region. Our scheme works with less overhead than the existing trust management schemes since multiple compromised nodes in a zone can be detected and revoked at a time. We also present the possible attacks against our scheme and describe the countermeasures of these attacks.
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paper_title: A quantitative trust establishment framework for reliable data packet delivery in MANETs

paper_content:

In mobile ad hoc networks (MANETs), a source node must rely on other nodes to forward its packets on multi-hop routes to the destination. Secure and reliable handling of packets by the intermediate nodes is difficult to ensure in an ad hoc environment. We propose a trust establishment scheme for MANETs which aims to improve the reliability of packet forwarding over multi-hop routes in the presence of potentially malicious nodes. Each node forms an "opinion" about each of the other nodes based on both first and second-hand observation data collected from the network. The opinion metric can be incorporated into ad hoc routing protocols to achieve reliable packet delivery even when a portion of the network exhibits malicious behavior. We present numerical results which demonstrate the effectiveness of the proposed trust establishment scheme.
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paper_title: Quantifying trust in mobile ad-hoc networks

paper_content:

This paper introduces a trust-domain based security architecture for mobile ad-hoc networks (MANETs). The aim of this architecture is twofold: to use trust as a basis to establish keys between nodes in a MANET, and to utilize trust as a metric for establishing secure distributed control in infrastructure-less MANETs. We define metrics for nodes to establish and manage trust, and use this mutual trust to make decisions on establishing group and pair-wise keys in the network. The impact of mobility of the nodes on trust establishment is considered and further its use as a means of propagating trust through the network is investigated. We introduce the concept of self-organizing trust-based physical-logical domains (PLDs) as a means of grouping nodes for distributed control in the network.
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paper_title: Provenance-Based Information Trustworthiness Evaluation in Multi-Hop Networks

paper_content:

In this paper, we present a trust model to evaluate the trustworthiness of information as well as the information publishing nodes based on the information provenance. We consider two factors in evaluating the provenance-based information trust: Path Similarity and Information Similarity. In multihop networks, information can flow through multiple hops from multiple paths. We model the similarity between different paths which deliver information about the same event and the similarity between two information items about the same event which are delivered through different paths. Both path and information similarity factors are considered in determining the trust of the information. This information trust is indeed used as a feedback factor to adaptively adjust trust of the nodes in the network. Detailed analysis of the proposed approach is presented along with simulation results for validation.
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paper_title: A dynamic trust model for mobile ad hoc networks

paper_content:

This paper introduces a trust model for mobile ad hoc networks. Initially each node is assigned a trust level. Then we use several approaches to dynamically update trust levels by using reports from threat detection tools, such as intrusion detection systems (IDS), located on all nodes in the network. The nodes neighboring to a node exhibiting suspicious behavior initiate trust reports. These trust reports are propagated through the network using one of our proposed methods. A source node can use the trust levels it establishes for other nodes to evaluate the security of routes to destination nodes. Using these trust levels as a guide, the source node can then select a route that meets the security requirements of the message to be transmitted. This paper demonstrates important concepts for establishing a collaborative, dynamic trust model and for using this model as an example to enhance the security of message routing in mobile ad hoc networks.
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paper_title: Modeling and Managing the Trust for Wireless and Mobile Ad Hoc Networks

paper_content:

With the growing popularity of wireless mobile ad hoc networks (MANETs), many security concerns have arisen from MANETs especially in that misbehaving nodes pose a major threat during the construction of a trusted network. A reputation-based trust system can track the behavior of nodes and thereby proceed by rewarding well-behaving nodes and punishing misbehaving ones. However, existing techniques are usually either energy-consuming or complicated since the relevant reputation information is propagated throughout the network. In this paper, we propose a novel trust computation and management system, called TOMS, which not only establishes the new concepts of trust and community but also includes both the trust computation model and trust management mechanism. Using the results of extensive simulations, we highlight the effectiveness and efficiency of our trust system in comparison to other trust schemes in traditional protocols. Thus, TOMS is shown to be dynamic, distributed, and efficient, as well as sensitive to suspicious behaviors and peers.
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paper_title: Trust Establishment In Pure Ad-hoc Networks

paper_content:

An ad-hoc network is a set of limited range wireless nodes that function in a cooperative manner so as to increase the overall range of the network. Each node in the network pledges to help its neighbours by passing packets to and fro, in return of a similar assurance from them. All is well if all participating nodes uphold such an altruistic behaviour. However, this is not always the case and often nodes are subjected to a variety of attacks by other nodes. These attacks range from naive passive eavesdropping to vicious battery draining attacks. Routing protocols, data, battery power and bandwidth are the common targets of these attacks. In order to overcome such attacks a number of routing protocols have been devised that use cryptographic algorithms to secure the routing mechanism, which in turn protects the other likely targets. A limiting requirement regarding these protocols is the reliance on an omnipresent, and often omniscient, trust authority. In our opinion, this reliance on a central entity is against the very nature of ad-hoc networks, which are supposed to be improvised and spontaneous. We present in this paper, a trust-based model for communication in ad-hoc networks that is based on individual experience rather than on a third party advocating trust levels. The model introduces the notion of belief and provides a dynamic measure of reliability and trustworthiness in pure ad-hoc networks.
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paper_title: Cluster-Based Trust Model against Attacks in Ad-Hoc Networks

paper_content:

In ad-hoc environments, all nodes have function to set themselves a route and build a network. It is important how trustable each node is in the environment. This study proposes the cluster-based trust model, and uses the model to discuss how you can solve some possible problems occurred in the network. The reputation from a neighboring node is applied to the calculation of the trust value. If the trust value of a truster is used as a weight, more sophisticated calculation of the trust value is available. When you create a cluster, all nodes in the cluster can fully trust the selected head, if entire nodes in the cluster participate in the head competition. And then, the head node issues the certificate that shows the trust level of each member node. If a node moves from one cluster to another, the trust level of the node is determined by the certificate issued by the previous cluster-head. The model proposed by this study can monitor the selfish behavior of nodes in the network and isolate the selfish nodes from the network to enhance the effectiveness throughout the network.
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paper_title: A Distributed Trust Model for Securing Mobile Ad Hoc Networks

paper_content:

In mobile ad hoc networks, the security enforcement and its implementation becoming increasingly difficult due to quasi-static nature of the mobile nodes (wireless communication devices), no fixed network topology and more importantly absence of centralized authority. In such networks, communication links between nodes may be bandwidth constrained, messages typically roamed in multi-hoped fashion, nodes may be powered by limited energy source and also have limited physical security. The major challenge in such networks is to give a robust security solution. The complexity of the problem is compounded by the fact that both active and passive attackers may present in the system, and nodes may not function properly in order to save its own energy by selective forwarding of the packets. This paper presents a distributed trust based security framework for ad hoc networks. We have proposed a clustering mechanism and security is enforced by local monitoring system by a new kind of nodes referred as guard nodes. This framework stems from cryptographic computation, which is not suitable in this scenario. The trust is computed depending upon some parameters which have a primary role in enforcing security and cooperation between the nodes. Also this solution conforms graceful leave and dynamic secure allocation of IP of the nodes.
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paper_title: Algorithms for dempster-shafer theory

paper_content:

The method of reasoning with uncertain information known as Dempster-Shafer theory arose from the reinterpretation and development of work of Arthur Dempster [Dempster, 1967; 1968] by Glenn Shafer in his book a mathematical theory of evidence [Shafer, 1976], and further publications e.g., [Shafer, 1981; 1990]. More recent variants of Dempster-Shafer theory include the Transferable Belief Model see e.g., [Smets, 1988; Smets and Keimes, 1994] and the Theory of Hints e.g., [Kohlas and Monney, 1995].
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paper_title: On trust models and trust evaluation metrics for ad hoc networks

paper_content:

Within the realm of network security, we interpret the concept of trust as a relation among entities that participate in various protocols. Trust relations are based on evidence created by the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation of trust evidence in ad hoc networks. Because of the dynamic nature of ad hoc networks, trust evidence may be uncertain and incomplete. Also, no preestablished infrastructure can be assumed. The evaluation process is modeled as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We give intuitive requirements and discuss design issues for any trust evaluation algorithm. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. We show that our semiring framework is flexible enough to express other trust models, most notably PGP's Web of Trust. Our scheme is shown to be robust in the presence of attackers.
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paper_title: The Eigentrust algorithm for reputation management in P2P networks

paper_content:

Peer-to-peer file-sharing networks are currently receiving much attention as a means of sharing and distributing information. However, as recent experience shows, the anonymous, open nature of these networks offers an almost ideal environment for the spread of self-replicating inauthentic files.We describe an algorithm to decrease the number of downloads of inauthentic files in a peer-to-peer file-sharing network that assigns each peer a unique global trust value, based on the peer's history of uploads. We present a distributed and secure method to compute global trust values, based on Power iteration. By having peers use these global trust values to choose the peers from whom they download, the network effectively identifies malicious peers and isolates them from the network.In simulations, this reputation system, called EigenTrust, has been shown to significantly decrease the number of inauthentic files on the network, even under a variety of conditions where malicious peers cooperate in an attempt to deliberately subvert the system.
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paper_title: A trust evaluation framework in distributed networks: Vulnerability analysis and defense against attacks

paper_content:

The performance of distributed networks depends on collaboration among distributed entities. To enhance security in distributed networks, such as ad hoc networks, it is important to evaluate the trustworthiness of participating entities since trust is the major driving force for collaboration. In this paper, we present a framework to quantitatively measure trust, model trust propagation, and defend trust evaluation systems against malicious attacks. In particular, we address the fundamental understanding of trust, quantitative trust metrics, mathematical properties of trust, dynamic properties of trust, and trust models. The attacks against trust evaluation are identified and defense techniques are developed. The proposed trust evaluation system is employed in ad hoc networks for securing ad hoc routing and assisting malicious node detection. The implementation is fully distributed. Simulations show that the proposed system can significantly improve network throughput as well as effectively detect malicious behaviors in ad hoc networks. Further, extensive simulations are performed to illustrate various attacks and the effectiveness of the proposed defense techniques.
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paper_title: An evidential model of distributed reputation management

paper_content:

For agents to function effectively in large and open networks, they must ensure that their correspondents, i.e., the agents they interact with, are trustworthy. Since no central authorities may exist, the only way agents can find trustworthy correspondents is by collaborating with others to identify those whose past behavior has been untrustworthy. In other words, finding trustworthy correspondents reduces to the problem of distributed reputation management.Our approach adapts the mathematical theory of evidence to represent and propagate the ratings that agents give to their correspondents. When evaluating the trustworthiness of a correspondent, an agent combines its local evidence (based on direct prior interactions with the correspondent) with the testimonies of other agents regarding the same correspondent. We experimentally studied this approach to establish that some important properties of trust are captured by it.
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paper_title: A Robust Reputation System for P2P and Mobile Ad-hoc Networks

paper_content:

Reputation systems can 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. We propose a fully distributed reputation system that can cope with false disseminated information. In our approach, everyone maintains a reputation rating and a trust rating about everyone else that they care about. From time to time first-hand reputation information is exchanged with others; using a modified Bayesian approach we designed and present in this paper, only second-hand reputation information that is not incompatible with the current reputation rating is accepted. Thus, reputation ratings are slightly modified by accepted information. Trust ratings are updated based on the compatibility of second-hand reputation information with prior reputation ratings. Data is entirely distributed: someone’s reputation and trust is the collection of ratings maintained by others. We enable redemption and prevent the sudden exploitation of good reputation built over time by introducing re-evaluation and reputation fading.
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paper_title: A Trust Model Robust to Slander Attacks in Ad Hoc Networks

paper_content:

Slander attacks represent a significant danger to distributed reputation systems. Malicious nodes may collude to lie about the reputation of a particular neighbor and cause serious damage to the overall trust evaluation system. This paper presents and analyzes a trust model robust to slander attacks in ad hoc networks. We provide nodes with a mechanism to build a trust relationship with its neighbors. The proposed model considers the recommendation of trustworthy neighbors and the previous experiences of the node itself. The interactions are limited to direct neighbors in order to scale on mobile networks. The results show the impact of slander attacks to our trust model. We analyze how the main parameters affect the trust evaluation process under a lying collusion attack. We show that our trust model tolerate almost 40% of liars.
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paper_title: Trust overlay networks for global reputation aggregation in P2P grid computing

paper_content:

This paper presents a new approach to trusted grid computing in a peer-to-peer (P2P) setting. Trust and security are essential to establish lasting working relationships among the peers. A P2P reputation system collects peer trust scores and aggregates them to yield a global reputation. We use a new trust overlay network (TON) to model the trust relationships among the peers. After analyzing the eBay transaction trace data, we discover a power-law distribution in user feedbacks. We develop a new reputation system, PowerTrust, to leverage power-law feedback characteristics. The PowerTrust system is built with locality-preserving hash functions and a lookahead random walk strategy. Dynamic system reconfiguration is enabled by the use of power nodes with well-established reputations. Through P2P simulation experiments on distributed file sharing and grid parameter-sweeping applications (PSA), we demonstrate the PowerTrust advantages in fast reputation convergence and accurate ranking of peer reputations. We report performance results with enhanced P2P query success rate, shortened job makespan, and increased job success rate in scalable P2P grid applications.
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paper_title: Surveying security analysis techniques in manet routing protocols

paper_content:

Suspension and steering device for a motorcycle front wheel carried by at least one support arm connected at its upper end to a suspension and shock absorber block wherein a handlebar or wheel is rotatively mounted on a vertical axis of a peak and is rotationally mounted around an axis at the upper end of an upper link inclined towards the front and the lower end of which is rotationally mounted about an axis at the upper end of a lower link inclined towards the front of the motorcycle from its lower end and which is rotationally connected to an axis whereby the handlebar is rotationally connected to the support arm, wherein the device being applicable to a motorcycle wheel steering assembly including a single lateral support arm for the wheel axle.
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paper_title: Trust Propagation in Small Worlds

paper_content:

The possibility of a massive, networked infrastructure of diverse entities partaking in collaborative applications with each other increases more and more with the proliferation of mobile devices and the development of ad hoc networking technologies. In this context, traditional security measures do not scale well. We aim to develop trust-based security mechanisms using small world concepts to optimise formation and propagation of trust amongst entities in these vast networks. In this regard, we surmise that in a very large mobile ad hoc network, trust, risk, and recommendations can be propagated through relatively short paths connecting entities. Our work describes the design of trust-formation and risk-assessment systems, as well as that of an entity recognition scheme, within the context of the small world network topology.
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paper_title: Social Trust in Opportunistic Networks

paper_content:

Opportunistic networks enable mobile users to participate in various social interactions with applications such as content distribution and micro-blogs. Because of their distributed nature, securing user interactions relies rather on trust than hard cryptography. Trust is often based on past user interactions such as in reputation systems relying on ratings. Yet, a more fundamental trust, social trust - assessing a user is genuine with honest intentions - must be established beforehand as many identities can be created easily (i.e., sybils). By leveraging the social network structure and its dynamics (conscious secure pairing and wireless contacts), we propose two complementary approaches for social trust establishment: explicit social trust and implicit social trust. Complexity, trust propagation and security issues are evaluated using real world complex graphs, synthetic mobility models and mobility traces. We show how our approach limits the maximum number of sybils independently of the network size and is more robust against manipulation attacks compared to state-of-the-art approaches such as PGP- like certification chains and distributed community detection algorithms.
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paper_title: Information theoretic framework of trust modeling and evaluation for ad hoc networks

paper_content:

The performance of ad hoc networks depends on cooperation and trust among distributed nodes. To enhance security in ad hoc networks, it is important to evaluate trustworthiness of other nodes without centralized authorities. In this paper, we present an information theoretic framework to quantitatively measure trust and model trust propagation in ad hoc networks. In the proposed framework, trust is a measure of uncertainty with its value represented by entropy. We develop four Axioms that address the basic understanding of trust and the rules for trust propagation. Based on these axioms, we present two trust models: entropy-based model and probability-based model, which satisfy all the axioms. Techniques of trust establishment and trust update are presented to obtain trust values from observation. The proposed trust evaluation method and trust models are employed in ad hoc networks for secure ad hoc routing and malicious node detection. A distributed scheme is designed to acquire, maintain, and update trust records associated with the behaviors of nodes' forwarding packets and the behaviors of making recommendations about other nodes. Simulations show that the proposed trust evaluation system can significantly improve the network throughput as well as effectively detect malicious behaviors in ad hoc networks.
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paper_title: Rendezvous based trust propagation to enhance distributed network security

paper_content:

Development of network of nodes connected with their trust values and the propagation of these trust values to far away nodes are basic operations of the modern day trustworthy networks. Trust can be exploited to mitigate the security threats in wireless network. Most of the existing trust propagation methods are based on flooding trust information, which puts a heavy burden on wireless communication, especially in ad hoc network and sensor network. In this paper, we propose a rendezvous based trust propagation scheme. Trust requester and trust provider send out trust-request and computed-trust tickets respectively, which will meet in some common rendezvous node with certain probability. Computed-trust will then be propagated to the requester. We carry out detailed performance evaluations of our scheme. The results show that our method achieves up to 66% overhead reduction in trust propagation compared to flood based methods.
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paper_title: Mobility helps security in ad hoc networks

paper_content:

Contrary to the common belief that mobility makes security more difficult to achieve, we show that node mobility can, in fact, be useful to provide security in ad hoc networks. We propose a technique in which security associations between nodes are established, when they are in the vicinity of each other, by exchanging appropriate cryptographic material. We show that this technique is generic, by explaining its application to fully self-organized ad hoc networks and to ad hoc networks placed under an (off-line) authority. We also propose an extension of this basic mechanism, in which a security association can be established with the help of a "friend". We show that our mechanism can work in any network configuration and that the time necessary to set up the security associations is strongly influenced by several factors, including the size of the deployment area, the mobility patterns, and the number of friends; we provide a detailed investigation of this influence.
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paper_title: Lightweight Distributed Trust Propagation

paper_content:

Using mobile devices, such as smart phones, people may create and distribute different types of digital content (e.g., photos, videos). One of the problems is that digital content, being easy to create and replicate, may likely swamp users rather than informing them. To avoid that, users may organize content producers that they know and trust in a web of trust. Users may then reason about this web of trust to form opinions about content producers with whom they have never interacted before. These opinions will then determine whether content is accepted. The process of forming opinions is called trust propagation. We design a mechanism for mobile devices that effectively propagates trust and that is lightweight and distributed (as opposed to previous work that focuses on centralized propagation). This mechanism uses a graph-based learning technique. We evaluate the effectiveness (predictive accuracy) of this mechanism against a large real-world data set. We also evaluate the computational cost of a J2ME implementation on a mobile phone.
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paper_title: Rendezvous based trust propagation to enhance distributed network security

paper_content:

Development of network of nodes connected with their trust values and the propagation of these trust values to far away nodes are basic operations of the modern day trustworthy networks. Trust can be exploited to mitigate the security threats in wireless network. Most of the existing trust propagation methods are based on flooding trust information, which puts a heavy burden on wireless communication, especially in ad hoc network and sensor network. In this paper, we propose a rendezvous based trust propagation scheme. Trust requester and trust provider send out trust-request and computed-trust tickets respectively, which will meet in some common rendezvous node with certain probability. Computed-trust will then be propagated to the requester. We carry out detailed performance evaluations of our scheme. The results show that our method achieves up to 66% overhead reduction in trust propagation compared to flood based methods.
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paper_title: Trust Type Based Semantic Web Services Assessment and Selection

paper_content:

As multiple service providers make themselves available on-line, the trustworthiness of services becomes significant. In Web services environments, services from different providers might have to be combined to establish a complete service. Although the individual service can be trusted, the composed service is not guaranteed against trust. Thus there must be a way to determine the composed service is trusted. This paper presents a trust type model to deduce the trust level of composed services. Then, we present a conceptual framework which enables trust based service discovery and selection. Using the inferred trust type of the composed service as the weight, we can evaluate service candidates and select the best match of them. Finally we describe the experiment results to validate our QoS based service selection.
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paper_title: Trust Propagation and Aggregation in Wireless Sensor Networks

paper_content:

In a multi-hop wireless sensor networks (WSNs), these sensor nodes cooperate each other to form a network without using any infrastructure, which has a wide application due to their easy of deployment. But the security of WSNs is still an issue. Traditionally cryptographic mechanisms such as authentication and encryption only address part of the problem of security in WSNs. Recently, the use of reputation systems has become an important mechanism in WSNs. The trust management is still a very important problem for reputation systems in WSNs. In this paper we develop a formal treatment of trust management for WSNs. The main contribution of our paper is that we define two kinds of operators, propagation and aggregation. It can combine and diffuse trust rating of nodes in WSNs. Simulation results and analysis show that our proposed operators can detect the misbehavior sensor fast and limited the effect of malicious report the trust rating.
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paper_title: Gossip-based computation of aggregate information

paper_content:

Over the last decade, we have seen a revolution in connectivity between computers, and a resulting paradigm shift from centralized to highly distributed systems. With massive scale also comes massive instability, as node and link failures become the norm rather than the exception. For such highly volatile systems, decentralized gossip-based protocols are emerging as an approach to maintaining simplicity and scalability while achieving fault-tolerant information dissemination. In this paper, we study the problem of computing aggregates with gossip-style protocols. Our first contribution is an analysis of simple gossip-based protocols for the computation of sums, averages, random samples, quantiles, and other aggregate functions, and we show that our protocols converge exponentially fast to the true answer when using uniform gossip. Our second contribution is the definition of a precise notion of the speed with which a node's data diffuses through the network. We show that this diffusion speed is at the heart of the approximation guarantees for all of the above problems. We analyze the diffusion speed of uniform gossip in the presence of node and link failures, as well as for flooding-based mechanisms. The latter expose interesting connections to random walks on graphs.
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paper_title: Gossip-based aggregation of trust in decentralized reputation systems

paper_content:

Decentralized Reputation Systems have recently emerged as a prominent method of establishing trust among self-interested agents in online environments. A key issue is the efficient aggregation of data in the system; several approaches have been proposed, but they are plagued by major shortcomings. ::: ::: We put forward a novel, decentralized data management scheme grounded in gossip-based algorithms. Rumor mongering is known to possess algorithmic advantages, and indeed, our framework inherits many of their salient features: scalability, robustness, globality, and simplicity. We also demonstrate that our scheme motivates agents to maintain a sparkling clean reputation, and is inherently impervious to certain kinds of attacks.
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paper_title: A WOWA-based Aggregation Technique on Trust Values Connected to Metadata 1

paper_content:

Metadata produced by members of a diverse community of peers tend to contain low-quality or even mutually inconsistent assertions. Trust values computed on the basis of users' feedback can improve metadata quality and reduce inconsistency, eliminating untrustworthy assertions. In this paper, we describe an approach to metadata creation and improvement, where community members express their opinions on the trustworthiness of each assertion. Our technique aggregates individual trustworthiness values to obtain a community-wide assessment of each assertion. We then apply a global trustworthiness threshold to eliminate some assertions to reduce the metadatabase's overall inconsistency.
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paper_title: Iterated Belief Revision, Revised

paper_content:

The AGM postulates for belief revision, augmented by the DP postulates for iterated belief revision, provide generally accepted criteria for the design of operators by which intelligent agents adapt their beliefs incrementally to new information. These postulates alone, however, are too permissive: They support operators by which all newly acquired information is canceled as soon as an agent learns a fact that contradicts some of its current beliefs. In this paper, we present a formal analysis of the deficiency of the DP postulates, and we show how to solve the problem by an additional postulate of independence. We give a representation theorem for this postulate and prove that it is compatible with AGM and DP.
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paper_title: Aggregation of Trust for Iterated Belief Revision in Probabilistic Logics

paper_content:

In this paper it is shown how communication about trust in a multi-agent system may be used to endow agents with belief change capabilities, in a probabilistic logical framework. Belief change operators are obtained in an intuitive, principled way using aggregation operators for trust-values. Under additional conditions, such change operators may be proved to be maxichoice. The present approach constitutes a sound method for autonomous uncertainty management in multi-agent systems.
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paper_title: Trust Representation and Aggregation in a Distributed Agent System

paper_content:

This paper considers a distributed system of software agents who cooperate in helping their users to find services, provided by different agents. The agents need to ensure that the service providers they select are trustworthy. Because the agents are autonomous and there is no central trusted authority, the agents help each other determine the trustworthiness of the service providers they are interested in. This help is rendered via a series of referrals to other agents, culminating in zero or more trustworthy service providers being identified. ::: ::: A trust network is a multiagent system where each agent potentially rates the trustworthiness of another agent. This paper develops a formal treatment of trust networks. At the base is a recently proposed representation of trust via a probability certainty distribution. The main contribution of this paper is the definition of two operators, concatenation and aggregation, using which trust ratings can be combined in a trust network. This paper motivates and establishes some important properties regarding these operators, thereby ensuring that trust can be combined correctly. Further, it shows that effects of malicious agents, who give incorrect information, are limited.
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paper_title: A calculus of trust and its application to PKI and identity management

paper_content:

We introduce a formal semantics based calculus of trust that explicitly represents trust and quantifies the risk associated with trust in public key infrastructure (PKI) and identity management (IdM). We then show by example how to formally represent trust relationships and quantitatively evaluate the risk associated with trust in public key certificate chains. In the context of choosing a certificate chain, our research shows that the shortest chain need not be the most trustworthy, and that it may make sense to compare the trustworthiness of a potential chain against a threshold to govern acceptance, changing the problem to finding a chain with sufficiently high trustworthiness. Our calculus also shows how quantified trust relationships among CAs can be combined to achieve an overall trust assessment of an offered certificate.
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paper_title: Composition and evaluation of trustworthy Web Services

paper_content:

Web service technology seamlessly enables integration of different software to fulfil dynamic business demands in a platform-neutral fashion. By means of standard interfaces, service requesters can obtain their desired functionalities through certain service discovery mechanism, and service providers can offer the functionality to service requesters without exposing details of provided services. However, the adoption of loosely coupled and distributed services will cause trustworthiness problems. In this paper, we use ontology to describe experience and we utilise statistical techniques along with Petri nets to conduct a trustworthy evaluation method for composite web services. The degree of trustworthiness of all involved services in an aggregated composite service will be evaluated by analysing past experiences so that the trustworthiness of the composite service could be estimated.
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paper_title: RLM: A General Model for Trust Representation and Aggregation

paper_content:

Reputation-based trust systems provide important capability in open and service-oriented computing environments. Most existing trust models fail to assess the variance of a reputation prediction. Moreover, the summation method, widely used for reputation feedback aggregation, is vulnerable to malicious feedbacks. This paper presents a general trust model, called RLM, for a more comprehensive and robust reputation evaluation. Concretely, we define a comprehensive reputation evaluation method based on two attributes: reputation value and reputation prediction variance. The reputation predication variance serves as a quality measure of the reputation value computed based on aggregation of feedbacks. For feedback aggregation, we propose the novel Kalman aggregation method, which can inherently support robust trust evaluation. To defend against malicious and coordinated feedbacks, we design the Expectation Maximization algorithm to autonomously mitigate the influence of a malicious feedback, and further apply the hypothesis test method to resist malicious feedbacks precisely. Through theoretical analysis, we demonstrate the robustness of the RLM design against adulating and defaming attacks, two popular types of feedback attacks. Our experiments show that the RLM model can effectively capture the reputation's evolution and outperform the popular summation-based trust models in terms of both accuracy and attack resilience. Concretely, under the attack of collusive malicious feedbacks, RLM offers higher robustness for the reputation prediction and a lower false positive rate for the malicious feedback detection.
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paper_title: Start Trusting Strangers? Bootstrapping and Prediction of Trust

paper_content:

Web-based environments typically span interactions between humans and software services. The management and automatic calculation of trust are among the key challenges of the future service-oriented Web. Trust management systems in large-scale systems, for example, social networks or service-oriented environments determine trust between actors by either collecting manual feedback ratings or by mining their interactions. However, most systems do not support bootstrapping of trust. In this paper we propose techniques and algorithms enabling the prediction of trust even when only few or no ratings have been collected or interactions captured. We introduce the concepts of mirroring and teleportation of trust facilitating the evolution of cooperation between various actors. We assume a user-centric environment, where actors express their opinions, interests and expertises by selecting and tagging resources. We take this information to construct tagging profiles, whose similarities are utilized to predict potential trust relations. Most existing similarity approaches split the three-dimensional relations between users, resources, and tags, to create and compare general tagging profiles directly. Instead, our algorithms consider (i) the understandings and interests of actors in tailored subsets of resources and (ii) the similarity of resources from a certain actor-group's point of view.
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paper_title: Reputation Prediction in Mobile Ad Hoc Networks Using RBF Neural Networks

paper_content:

Security is one of the major challenges in the design and implementation of protocols for mobile ad hoc networks (MANETs). ‘Cooperation for corporate well-being’ is one of the major principles being followed in current research to formulate various security protocols. In such systems, nodes establish trust-based interactions based on their reputation which is determined by node activities in the past. In this paper we propose the use of a Radial Basis Function-Neural Network (RBF-NN) to estimate the reputation of nodes based on their internal attributes as opposed to their observed activity, e.g., packet traffic. This technique is conducive to prediction of the reputation of a node before it portrays any activities, for example, malicious activities that could be potentially predicted before they actually begin. This renders the technique favorable for application in trust-based MANET defense systems to enhance their performance. In this work we were able to achieve an average prediction performance of approximately 91% using an RBF-NN to predict the reputation of the nodes in the MANET.
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paper_title: Autonomic trust prediction for pervasive systems

paper_content:

In recent years, various trust management models based on the human notion of trust have been proposed to support trust-aware decision making in pervasive systems. However, the degree of subjectivity embedded in human trust often clashes with the requirements imposed by the target scenario: on one hand, pervasive computing calls for autonomic and light-weight systems that impose minimum burden on the user of the device (and on the device itself); on the other hand, computational models of human trust seem to demand a large amount of user input and physical resources. The result is often a computational trust model that does not 'compute': either the degree of subjectivity it offers is limited, or its complexity compromises its usability. In this paper, we present an accurate and efficient trust prediction model that is based on a basic Kalman filter. We discuss simulation results to demonstrate that the predictor is capable of capturing the natural disposition to trust of the user of the device, while being autonomic and light-weight.
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paper_title: Formal Analysis of Models for the Dynamics of Trust Based on Experiences

paper_content:

The aim of this paper is to analyse and formalise the dynamics of trust in the light of experiences. A formal framework is introduced for the analysis and specification of models for trust evolution and trust update. Different properties of these models are formally defined.
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paper_title: Trust No One: Evaluating Trust-based Filtering for Recommenders

paper_content:

To be successful recommender systems must gain the trust of users. To do this they must demonstrate their ability to make reliable predictions. We argue that collaborative filtering recommendation algorithms can benefit from explicit models of trust to inform their predictions. We present one such model of trust along with a cost-benefit analysis that focuses on the classical trade-off that exists between recommendation coverage and prediction accuracy.
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paper_title: Reputation Prediction in Mobile Ad Hoc Networks Using RBF Neural Networks

paper_content:

Security is one of the major challenges in the design and implementation of protocols for mobile ad hoc networks (MANETs). ‘Cooperation for corporate well-being’ is one of the major principles being followed in current research to formulate various security protocols. In such systems, nodes establish trust-based interactions based on their reputation which is determined by node activities in the past. In this paper we propose the use of a Radial Basis Function-Neural Network (RBF-NN) to estimate the reputation of nodes based on their internal attributes as opposed to their observed activity, e.g., packet traffic. This technique is conducive to prediction of the reputation of a node before it portrays any activities, for example, malicious activities that could be potentially predicted before they actually begin. This renders the technique favorable for application in trust-based MANET defense systems to enhance their performance. In this work we were able to achieve an average prediction performance of approximately 91% using an RBF-NN to predict the reputation of the nodes in the MANET.
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paper_title: A Survey of Trust and Reputation Systems for Online Service Provision

paper_content:

Trust and reputation systems represent a significant trend in decision support for Internet mediated service provision. The basic idea is to let parties rate each other, for example after the completion of a transaction, and use the aggregated ratings about a given party to derive a trust or reputation score, which can assist other parties in deciding whether or not to transact with that party in the future. A natural side effect is that it also provides an incentive for good behaviour, and therefore tends to have a positive effect on market quality. Reputation systems can be called collaborative sanctioning systems to reflect their collaborative nature, and are related to collaborative filtering systems. Reputation systems are already being used in successful commercial online applications. There is also a rapidly growing literature around trust and reputation systems, but unfortunately this activity is not very coherent. The purpose of this article is to give an overview of existing and proposed systems that can be used to derive measures of trust and reputation for Internet transactions, to analyse the current trends and developments in this area, and to propose a research agenda for trust and reputation systems.
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paper_title: An evidential model of distributed reputation management

paper_content:

For agents to function effectively in large and open networks, they must ensure that their correspondents, i.e., the agents they interact with, are trustworthy. Since no central authorities may exist, the only way agents can find trustworthy correspondents is by collaborating with others to identify those whose past behavior has been untrustworthy. In other words, finding trustworthy correspondents reduces to the problem of distributed reputation management.Our approach adapts the mathematical theory of evidence to represent and propagate the ratings that agents give to their correspondents. When evaluating the trustworthiness of a correspondent, an agent combines its local evidence (based on direct prior interactions with the correspondent) with the testimonies of other agents regarding the same correspondent. We experimentally studied this approach to establish that some important properties of trust are captured by it.
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paper_title: Formal Analysis of Models for the Dynamics of Trust Based on Experiences

paper_content:

The aim of this paper is to analyse and formalise the dynamics of trust in the light of experiences. A formal framework is introduced for the analysis and specification of models for trust evolution and trust update. Different properties of these models are formally defined.
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paper_title: A Survey of Trust and Reputation Management Systems in Wireless Communications

paper_content:

Trust is an important concept in human interactions which facilitates the formation and continued existence of functional human societies. In the first decade of the 21st century, computational trust models have been applied to solve many problems in wireless communication systems. This cross-disciplinary research has yielded many innovative solutions. In this paper, we examine the latest methods which have been proposed by researchers to manage trust and reputation in wireless communication systems. Specifically, we survey the state of the art in the application of trust models in the fields of mobile ad hoc networks (MANETs), wireless sensor networks (WSNs), and cognitive radio networks (CRNs). We classify the mainstream methods into natural categories and illustrate how they complement each other in achieving design goals. Major research directions are also outlined.
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paper_title: Trust- and clustering-based authentication services in mobile ad hoc networks

paper_content:

A mobile ad hoc network is a kind of wireless communication network that does not rely on a fixed infrastructure and is lack of any centralized control. These characteristics make it vulnerable to security attack, so protecting the security of the network is essential. Like many distributed systems, security in ad hoc networks widely relies on the use of key management mechanisms. However, traditional key management systems are not appropriate for them. We aim at providing a secure and distributed authentication service in ad hoc networks. We propose a secure public key authentication service based on our trust model and network model to prevent nodes from obtaining false public keys of the others when there are malicious nodes in the network. We perform an overall evaluation of our proposed approach by simulations. The experimental results indicate clear advantages of our approach in providing effective security in mobile ad hoc networks.
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paper_title: An Effective Trust Establishment Scheme for Authentication in Mobile Ad Hoc Networks

paper_content:

Distributed authentication has the property of high security compared with existing authentication schemes. However, its success ratio for authentication may be not high, especially in large-scale Mobile Ad- Hoc Networks (MANETs). In order to address this issue, we propose a hybrid authentication scheme which integrates the chained authentication with the distributed authentication. When a node can't find enough authentication nodes in its one-hop neighborhood to authenticate itself it requests its neighboring nodes to find a certificate chain to do so through the chained authentication. Hence, our scheme overcomes the drawbacks in terms of success ratio for authentication. Theoretical analysis and simulation studies show that, compared with the chained authentication schemes, our scheme is more scalable and it can increase the success ratio for authentication, without sacrificing the security requirement.
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paper_title: A formal model for trust in dynamic networks

paper_content:

We propose a formal model of trust informed by the Global Computing scenario and focusing on the aspects of trust formation, evolution, and propagation. The model is based on a novel notion of trust structures which, building on concepts from trust management and domain theory, feature at the same time a trust and an information partial order.
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paper_title: Trust Enhanced Secure Mobile Ad-Hoc Network Routing

paper_content:

In recent years, several trust and reputation models have been proposed to enhance the security of mobile ad hoc networks. However, they either fail to capture evidence of trustworthiness within the limitations of the network, or introduce additional problems while capturing the evidence. In this paper, we propose a reputation-based trust model known as secure MANET routing with trust intrigue (SMRTI). In our model, the evidence of trustworthiness is captured in an efficient manner and from broader perspectives including direct interactions with neighbours, observing interactions of neighbours and through recommendations. SMRTI captures evidence from direct interactions with neighbours in order to identify their benign and malicious behaviours. It also captures evidence for misbehaviours by observing the interactions of neighbours. Lastly, the evidence captured from recommendations is used to summarize the benign behaviour of multi-hop nodes. Unlike other models, we adopt a novel approach to capture evidence from recommendations, which eliminates recommender's bias, free-riding, and honest- elicitation. SMRTI utilizes the captured evidence to predict whether a node is either benign or misbehaving. It then applies the prediction to enhance the security of communications depending on the decision policies, such as whether to send a packet to or forward a packet on behalf of other nodes. Finally, we demonstrate the performance of our model through simulation results.
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paper_title: A Mechanism for Detecting and Responding to Misbehaving Nodes in Wireless Networks

paper_content:

While mechanisms exist to instantiate common security functionality such as confidentiality and integrity, little has been done to define a mechanism for identification and remediation of devices engaging in behavior deemed inappropriate. This ability is particularly relevant as devices become increasingly adaptive through the development of software-defined and frequency agile radios. Adaptive devices can alter their behavior in a way that is noncompliant to a given set of standards and thus cause problems for other compliant devices, We address this deficiency by developing and assessing a mechanism for detecting misbehaving nodes in wireless systems. While we developed our system on an 802.11 network, the same approach could readily be applied to other wireless networks. Our mechanism is based on a reputation-enabled intrusion detection system, in which a centralized trust authority monitors traffic and collects secondhand information on potentially misbehaving nodes. The system integrates a mixture of alarms and reports to calculate a reputation vector of all nodes in the system. An XML based policy engine is used to detect policy violations. These mechanisms are built to be flexible and extensible in order to deal with the issues arising out of software programmable devices. In extending beyond traditional intrusion detection, our approach will incorporate physical layer information, such as power and frequency use, in determining improper behavior. In evaluating the system, we consider how our mechanism, 1) impacts system performance, 2) correctly identifies misbehaving nodes, 3) addresses "bad mouthing" and 4) resists collusion.
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paper_title: Mobility Reduces Uncertainty in MANETs

paper_content:

Evaluating and quantifying trust stimulates collaboration in mobile ad hoc networks (MANETs). Many existing reputation systems sharply divide the trust value into right or wrong, thus ignoring another core dimension of trust: uncertainty. As uncertainty deeply impacts a node's anticipation of others' behavior and decisions during interaction, we include uncertainty in the reputation system. Specifically, we use an uncertainty metric to directly reflect a node's confidence in the sufficiency of its past experience, and study how the collection of trust information may affect uncertainty in nodes' opinions. Higher uncertainty leads to higher transaction cost and reduced acceptance of communication and cooperation. After defining a way to reveal and compute the uncertainty in trust opinions, we exploit mobility, one of the important characteristics of MANETs, to efficiently reduce uncertainty and to speed up trust convergence. A two-level mobility assisted uncertainty reduction scheme (MAURS) that offers controllable trade-off between time and cost to achieve a convergence objective of trust is also provided. Extensive analytical and simulation results are presented to support our proposal.
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paper_title: Trust Based Malicious Nodes Detection in MANET

paper_content:

Node misbehavior due to selfish or malicious intention could significantly degrade the performance of MANET because most existing routing protocols in MANET are aiming at finding most efficiency path. To deal with misbehavior in MANET, an incentive mechanism should be integrated into routing decision-making. In this paper firstly we review existing techniques for secure routing, and then propose to use trust vector model based routing protocols. Each node would evaluate its own trust vector parameters about neighbors through monitoring neighbors' pattern of traffic in network. At the same time, trust dynamics is included in term of robustness. Then we evaluate the performance of the proposed mechanism by modifying Dynamic Source Routing (DSR) so that each node has a dynamic changing "trust vector" for its neighbors' behaviors. We also compare the simulation results of with and without the proposed mechanism. The simulation results demonstrate that the proposed mechanisms can effectively detect malicious nodes and mitigate black hole attacks.
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paper_title: An Approach to Evaluate Data Trustworthiness Based on Data Provenance

paper_content:

Today, with the advances of information technology, individual people and organizations can obtain and process data from different sources. It is critical to ensure data integrity so that effective decisions can be made based on these data. An important component of any solution for assessing data integrity is represented by techniques and tools to evaluate the trustworthiness of data provenance. However, few efforts have been devoted to investigate approaches for assessing how trusted the data are, based in turn on an assessment of the data sources and intermediaries. To bridge this gap, we propose a data provenance trust model which takes into account various factors that may affect the trustworthiness and, based on these factors, assigns trust scores to both data and data providers. Such trust scores represent key information based on which data users may decide whether to use the data and for what purposes.
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paper_title: Assessing the trustworthiness of location data based on provenance

paper_content:

Trustworthiness of location information about particular individuals is of particular interest in the areas of forensic science and epidemic control. In many cases, location information is not precise and may include fraudulent information. With the growth of mobile computing and positioning systems, e.g., GPS and cell phones, it has become possible to trace the location of moving objects. Such Systems provide us an opportunity to find out the true locations of individuals. In this paper, we present a model to compute trustworthiness of the location information of an individual based on different evidences from different sources. We also introduce a collusion attack that may bias the computation. Based on the analysis of the attack, we present the algorithm to detect and reduce the effect of collusion attacks. Our experimental results show the efficiency and effectiveness of our approach.
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paper_title: A Mechanism for Detecting and Responding to Misbehaving Nodes in Wireless Networks

paper_content:

While mechanisms exist to instantiate common security functionality such as confidentiality and integrity, little has been done to define a mechanism for identification and remediation of devices engaging in behavior deemed inappropriate. This ability is particularly relevant as devices become increasingly adaptive through the development of software-defined and frequency agile radios. Adaptive devices can alter their behavior in a way that is noncompliant to a given set of standards and thus cause problems for other compliant devices, We address this deficiency by developing and assessing a mechanism for detecting misbehaving nodes in wireless systems. While we developed our system on an 802.11 network, the same approach could readily be applied to other wireless networks. Our mechanism is based on a reputation-enabled intrusion detection system, in which a centralized trust authority monitors traffic and collects secondhand information on potentially misbehaving nodes. The system integrates a mixture of alarms and reports to calculate a reputation vector of all nodes in the system. An XML based policy engine is used to detect policy violations. These mechanisms are built to be flexible and extensible in order to deal with the issues arising out of software programmable devices. In extending beyond traditional intrusion detection, our approach will incorporate physical layer information, such as power and frequency use, in determining improper behavior. In evaluating the system, we consider how our mechanism, 1) impacts system performance, 2) correctly identifies misbehaving nodes, 3) addresses "bad mouthing" and 4) resists collusion.
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paper_title: Provenance-Based Information Trustworthiness Evaluation in Multi-Hop Networks

paper_content:

In this paper, we present a trust model to evaluate the trustworthiness of information as well as the information publishing nodes based on the information provenance. We consider two factors in evaluating the provenance-based information trust: Path Similarity and Information Similarity. In multihop networks, information can flow through multiple hops from multiple paths. We model the similarity between different paths which deliver information about the same event and the similarity between two information items about the same event which are delivered through different paths. Both path and information similarity factors are considered in determining the trust of the information. This information trust is indeed used as a feedback factor to adaptively adjust trust of the nodes in the network. Detailed analysis of the proposed approach is presented along with simulation results for validation.
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paper_title: Managing the pedigree and quality of information in dynamic information sharing environments

paper_content:

The quality of information is crucial for decision making in many mission-critical applications such as battlefield operations and intelligence analysis. However, as the system becomes larger and more diverse, it is becoming increasingly difficult to assess the quality of information from various operators or data sources. In this paper we propose an agent-based approach to managing the quality of information, e.g., its trustworthiness, in network centric information sharing environments, where software agents collaborate with each other to automatically represent and assess the trustworthiness of information from its pedigree within the framework of Dempster-Shafer theory.
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paper_title: The Challenge of Assuring Data Trustworthiness

paper_content:

With the increased need of data sharing among multiple organizations, such as government organizations, financial corporations, medical hospitals and academic institutions, it is critical to ensure that data is trustworthy so that effective decisions can be made based on these data. In this paper, we first discuss motivations and requirement for data trustworthiness. We then present an architectural framework for a comprehensive system for trustworthiness assurance. We then discuss an important issue in our framework, that is, the evaluation of data provenance and survey a trust model for estimating the confidence level of the data and the trust level of data providers. By taking into account confidence about data provenance, we introduce an approach for policy observing query evaluation. We highlight open research issues and research directions throughout the paper.
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paper_title: Cooperative games, phase transitions on graphs and distributed trust in MANET

paper_content:

Mobile adhoc networks (MANET) provide a relative new paradigm of wireless networking, which poses several formidable challenges for control, monitoring and management, due to the basically "infrastructureless" nature of these networks. Security is viewed in this paper as part of the control-operations-management functionality of MANET. An important and critical part of security is trust establishment and maintenance. We provide a description of distributed trust within the MANET framework that consists of two major components: (a) trust document distribution; and (b) distributed trust computation. Within (a) we summarize our earlier work on swarm-intelligence based trust document distribution schemes, including their major advantages as compared to other schemes as well as their performance. This paper is primarily addressing our new results within (b). Here we show that under a variety of schemes for distributed trust computation and establishment we have established strong connections with various components of the theory of random graphs. In this context we demonstrate how phase transitions (in this case they mean node transitions from nontrusted to trusted) can appear within a MANET. We link the existence and analysis of such phase transitions to dynamic cooperative games. We demonstrate that dynamic cooperative games provide a natural framework for analyzing several problems for MANET. We also demonstrate the fundamental influence of the topology of the MANET on these phase transitions. Finally we conclude with a preliminary description of results that describe the effects of mobility and topology change on these trust establishment schemes.
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paper_title: Social network, social trust and shared goals in organizational knowledge sharing

paper_content:

The aim of our study was to further develop an understanding of social capital in organizational-knowledge-sharing. We first developed a measurement tool and then a theoretical framework in which three social capital factors (social network, social trust, and shared goals) were combined with the theory of reasoned action; their relationships were then examined using confirmatory factoring analysis. We then surveyed of 190 managers from Hong Kong firms, we confirm that a social network and shared goals significantly contributed to a person's volition to share knowledge, and directly contributed to the perceived social pressure of the organization. The social trust has however showed no direct effect on the attitude and subjective norm of sharing knowledge.
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Title: Trust Computations and Trust Dynamics in Mobile Adhoc Networks: A Survey

Section 1: Introduction
Description 1: Introduce the importance of trust in MANETs, the challenges of distributed trust computations, and the objective of the survey.

Section 2: Trust Definition, Metrics, and Properties
Description 2: Discuss various definitions of trust, the metrics used for evaluating trust, and the properties that influence trust computations in MANETs.

Section 3: Trust Computations
Description 3: Summarize different approaches to trust computations including distributed and centralized methods.

Section 4: Distributed Trust Computations
Description 4: Detail the methods and mechanisms of distributed trust computations such as direct neighbour sensing, recommendation-based trust, and hybrid methods.

Section 5: Centralized Trust Establishment
Description 5: Describe the trust computation with the involvement of centralized agents including cluster heads and reputation assistants.

Section 6: Attack Model
Description 6: Identify and explain possible attacks on trust systems in MANETs, and compare trust computing schemes based on their resistance to these attacks.

Section 7: Dynamics of Trust
Description 7: Explore the evolution and dynamics of trust including its propagation, aggregation, and prediction.

Section 8: Application of Trust in Security
Description 8: Analyze various security applications of trust management in MANETs, focusing particularly on malicious node detection and information trustworthiness.

Section 9: Conclusion and Future Work
Description 9: Summarize the survey findings, discuss the gaps in current research, and suggest directions for future work.