A Survey on Trust Management for Mobile Ad Hoc Networks
---
paper_title: Why Trust is not Proportional to Risk

paper_content:

Trust is inherently related to risk, but for trust assessment to be integrated with the management of the risks involved in trust based cooperation, the exact relation must be well understood. Existing literature on trust management is neither clear nor unambiguous on this issue. This paper discusses notions of trust as presented within the disciplines of sociology and economics for the purpose of motivating trust management. A critical survey of state of the art literature on trust management is provided, where weaknesses and ambiguities with respect to clarifying the notion of trust are discussed. An analysis and explanation of the exact relationship between risk and trust is presented, and implications of the subjectivity of trust relations are accounted for
---
paper_title: Why Trust is not Proportional to Risk

paper_content:

Trust is inherently related to risk, but for trust assessment to be integrated with the management of the risks involved in trust based cooperation, the exact relation must be well understood. Existing literature on trust management is neither clear nor unambiguous on this issue. This paper discusses notions of trust as presented within the disciplines of sociology and economics for the purpose of motivating trust management. A critical survey of state of the art literature on trust management is provided, where weaknesses and ambiguities with respect to clarifying the notion of trust are discussed. An analysis and explanation of the exact relationship between risk and trust is presented, and implications of the subjectivity of trust relations are accounted for
---
paper_title: An Objective Trust Management Framework for Mobile Ad Hoc Networks

paper_content:

In mobile ad hoc networks (MANETs), each node should not only work for itself, but should be cooperative with other nodes. Under such environment, some nodes may misbehave for individual interests. Currently two categories of trust management frameworks, reputation-based framework and trust establishment framework, are used to guarantee nodes to perform normal behavior. However, in reputation-based framework, it is unreasonable that only one parameter, trust value, is considered. Meanwhile, the trust establishment framework is vulnerable under the selective misbehavior attack, by which the attacker performs different behaviors to different nodes. To solve these problems, we propose an objective trust management framework (OTMF) for MANETs, by which one node evaluates the trustworthiness of another node objectively based not only on direct observations, but on second-hand information. To compare the OTMF with the existing frameworks, we provide performance evaluation. The evaluation results show that the OTMF can obtain more reliable trust than the reputation-based framework and can prevent the selective misbehavior attack more effectively than the trust establishment framework.
---
paper_title: Toward a decentralized trust-based access control system for dynamic collaboration

paper_content:

As ad-hoc collaborative environments become more common, the need for access control becomes more imperative. Centralized access control determination fails to work in mobile ad-hoc networking environments, as the information necessary for pre-configuration is not available. This situation is exacerbated by the dynamic nature of the environment's membership, so that the time and resources expended in offline management are largely wasted. This paper presents a decentralized access control system that implements sociological trust constructs in a quantitative system to evaluate interaction partners. A distributed, node-centric approach to reputation management processes nodal behavior feedback and provides a reputation index that nodes use to determine trustworthiness their peers before establishing associations. The availability of a reputation index gives a measure of expectation of a peer's behavior, based on past performance, and makes a MANET a more distributed operational environment.
---
paper_title: Trust Management in Distributed Systems

paper_content:

Distributed systems such as the Internet, peer-to-peer networks, and mobile ad hoc networks involve numerous entities, many of which haven't previously interacted. Trust management can help minimize risk and ensure the network activity of benign entities in distributed systems. This article presents different trust models. It also discusses trust management in P2P system
---
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 Survey

paper_content:

Trust is an important tool in human life, as it enables people to cope with the uncertainty caused by the free will of others. Uncertainty and uncontrollability are also issues in computer-assisted collaboration and electronic commerce in particular. A computational model of trust and its implementation can alleviate this problem. ::: ::: This survey is directed to an audience wishing to familiarize themselves with the field, for example to locate a research target or implement a trust management system. It concentrates on providing a general overview of the state of the art, combined with examples of things to take into consideration both when modelling trust in general and building a solution for a certain phase in trust management, be it trust relationship initialization, updating trust based on experience or determining what trust should have an effect on.
---
paper_title: Trust Management in Distributed Systems

paper_content:

Distributed systems such as the Internet, peer-to-peer networks, and mobile ad hoc networks involve numerous entities, many of which haven't previously interacted. Trust management can help minimize risk and ensure the network activity of benign entities in distributed systems. This article presents different trust models. It also discusses trust management in P2P system
---
paper_title: Why Trust is not Proportional to Risk

paper_content:

Trust is inherently related to risk, but for trust assessment to be integrated with the management of the risks involved in trust based cooperation, the exact relation must be well understood. Existing literature on trust management is neither clear nor unambiguous on this issue. This paper discusses notions of trust as presented within the disciplines of sociology and economics for the purpose of motivating trust management. A critical survey of state of the art literature on trust management is provided, where weaknesses and ambiguities with respect to clarifying the notion of trust are discussed. An analysis and explanation of the exact relationship between risk and trust is presented, and implications of the subjectivity of trust relations are accounted for
---
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.
---
paper_title: Toward a decentralized trust-based access control system for dynamic collaboration

paper_content:

As ad-hoc collaborative environments become more common, the need for access control becomes more imperative. Centralized access control determination fails to work in mobile ad-hoc networking environments, as the information necessary for pre-configuration is not available. This situation is exacerbated by the dynamic nature of the environment's membership, so that the time and resources expended in offline management are largely wasted. This paper presents a decentralized access control system that implements sociological trust constructs in a quantitative system to evaluate interaction partners. A distributed, node-centric approach to reputation management processes nodal behavior feedback and provides a reputation index that nodes use to determine trustworthiness their peers before establishing associations. The availability of a reputation index gives a measure of expectation of a peer's behavior, based on past performance, and makes a MANET a more distributed operational environment.
---
paper_title: SybilGuard: defending against sybil attacks via social networks

paper_content:

Peer-to-peer and other decentralized, distributed systems are known to be particularly vulnerable to sybil attacks. In a sybil attack, a malicious user obtains multiple fake identities and pretends to be multiple, distinct nodes in the system. By controlling a large fraction of the nodes in the system, the malicious user is able to ldquoout voterdquo the honest users in collaborative tasks such as Byzantine failure defenses. This paper presents SybilGuard, a novel protocol for limiting the corruptive influences of sybil attacks. Our protocol is based on the ldquosocial networkrdquo among user identities, where an edge between two identities indicates a human-established trust relationship. Malicious users can create many identities but few trust relationships. Thus, there is a disproportionately small ldquocutrdquo in the graph between the sybil nodes and the honest nodes. SybilGuard exploits this property to bound the number of identities a malicious user can create. We show the effectiveness of SybilGuard both analytically and experimentally.
---
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: A Distributed Light-Weight Authentication Model for Ad-hoc Networks

paper_content:

In this work we present a security model for low-value transactions in ad-hoc networks in which we focus on authentication since this is the core requirement for commercial transactions. After a brief introduction to the ad-hoc networking paradigm we give a survey of various existing models and analyze them in terms of scope and applications. It is concluded that no appropriate and satisfactory model for low-value transactions in ad-hoc networks has been developed to date. Our new model is derived from previous models dealing with trust and security in ad-hoc networks, and does not require devices with strong processors as public-key systems. We base the model on a recommendation and reference protocol that is inspired by human behavior and that is in accordance with the very nature of ad-hoc networks.
---
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.
---
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.
---
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: Performance Analysis of the CONFIDANT Protocol: Cooperation of Nodes – Fairness In Dynamic Ad Hoc Networks

paper_content:

Mobile ad-hoc networking works properly only if the participating nodes cooperate in routing and forwarding. However, it may be advantageous for individual nodes not to cooperate. We propose a protocol, called CONFIDANT, for making misbehavior unattractive; it is based on selective altruism and utilitarianism. It aims at detecting and isolating misbehaving nodes, thus making it unattractive to deny cooperation. Trust relationships and routing decisions are based on experienced, observed, or reported routing and forwarding behavior of other nodes. The detailed implementation of CONFIDANT in this paper assumes that the network layer is based on the Dynamic Source Routing (DSR) protocol. We present a performance analysis of DSR fortified by CONFIDANT and compare it to regular defenseless DSR. It shows that a network with CONFIDANT and up to 60% of misbehaving nodes behaves almost as well as a benign network, in sharp contrast to a defenseless network. All simulations have been implemented and performed in GloMoSim.
---
paper_title: Robust cooperative trust establishment for MANETs

paper_content:

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.
---
paper_title: Nodes bearing grudges: towards routing security, fairness, and robustness in mobile ad hoc networks

paper_content:

Devices in mobile ad hoc networks work as network nodes and relay packets originated by other nodes. Mobile ad hoc networks can work properly only if the participating nodes cooperate in routing and forwarding. For individual nodes it might be advantageous not to cooperate. The new routing protocol extensions presented in this paper make it possible to detect and isolate misbehaving nodes, thus making denying cooperation undesirable. In the presented scheme, trust relationships and routing decisions are made based on experienced, observed, or reported routing and forwarding behavior of other nodes. A hybrid scheme of selective altruism and utilitarianism is presented to strengthen mobile ad hoc network protocols in their resistance to security attacks, while aiming at keeping network throughput high. This paper focuses particularly on the network layer using the dynamic source routing (DSR) protocol as an example.
---
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: Ant-based adaptive trust evidence distribution in MANET

paper_content:

Due to the lack of infrastructure and vulnerability of wireless links, security in ad hoc networks is considered to be much more difficult than in traditional hierarchical networks. Building the trust relationship between entities is a fundamental problem in ad hoc networks, since the availability of servers, which distribute trust certificates, is not guaranteed. Furthermore, the existence of any trusted server might not be assumed either. Therefore, the commonly used key distribution center (KDC) and certification authority (CA) are not applicable in such highly autonomous environments. We propose a scheme for the distribution of trust certificates, which is completely distributed and adaptive to mobility. Our scheme is based on the swarm intelligence paradigm, which has been used for routing both in wired and wireless networks. Our simulations in ns-2 show that it performs very well in ad hoc environments.
---
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.
---
paper_title: Cognitive networks

paper_content:

This paper presents a definition and framework for a novel type of adaptive data network: the cognitive network. In a cognitive network, the collection of elements that make up the network observes network conditions and then, using prior knowledge gained from previous interactions with the network, plans, decides and acts on this information. Cognitive networks are different from other "intelligent" communication technologies because these actions are taken with respect to the end-to-end goals of a data flow. In addition to the cognitive aspects of the network, a specification language is needed to translate the user's end-to-end goals into a form understandable by the cognitive process. The cognitive network also depends on a software adaptable network that has both an external interface accessible to the cognitive network and network status sensors. These devices are used to provide control and feedback. The paper concludes by presenting a simple case study to illustrate a cognitive network and its framework
---
paper_title: SybilGuard: defending against sybil attacks via social networks

paper_content:

Peer-to-peer and other decentralized, distributed systems are known to be particularly vulnerable to sybil attacks. In a sybil attack, a malicious user obtains multiple fake identities and pretends to be multiple, distinct nodes in the system. By controlling a large fraction of the nodes in the system, the malicious user is able to ldquoout voterdquo the honest users in collaborative tasks such as Byzantine failure defenses. This paper presents SybilGuard, a novel protocol for limiting the corruptive influences of sybil attacks. Our protocol is based on the ldquosocial networkrdquo among user identities, where an edge between two identities indicates a human-established trust relationship. Malicious users can create many identities but few trust relationships. Thus, there is a disproportionately small ldquocutrdquo in the graph between the sybil nodes and the honest nodes. SybilGuard exploits this property to bound the number of identities a malicious user can create. We show the effectiveness of SybilGuard both analytically and experimentally.
---
paper_title: Trust Management Survey

paper_content:

Trust is an important tool in human life, as it enables people to cope with the uncertainty caused by the free will of others. Uncertainty and uncontrollability are also issues in computer-assisted collaboration and electronic commerce in particular. A computational model of trust and its implementation can alleviate this problem. ::: ::: This survey is directed to an audience wishing to familiarize themselves with the field, for example to locate a research target or implement a trust management system. It concentrates on providing a general overview of the state of the art, combined with examples of things to take into consideration both when modelling trust in general and building a solution for a certain phase in trust management, be it trust relationship initialization, updating trust based on experience or determining what trust should have an effect on.
---

Title: A Survey on Trust Management for Mobile Ad Hoc Networks

Section 1: What is Trust?
Description 1: This section introduces the basic concept of trust and its importance in protocol design for network systems.

Section 2: Relation among Trust, Trustworthiness and Risk
Description 2: This section explores the relationship between trust and risk, illustrating how it affects collaborative network environments.

Section 3: Properties of Trust
Description 3: This section discusses the essential properties of trust, such as transitivity, asymmetry, and personalization from social network perspectives.

Section 4: Characteristics of Trust in MANETs
Description 4: This section details the unique characteristics of trust specific to Mobile Ad Hoc Networks (MANETs).

Section 5: Trust Management for MANETs
Description 5: This section differentiates trust management from reputation management and discusses the main components and processes involved in managing trust for MANETs.

Section 6: Classifications
Description 6: This section introduces various frameworks and classifications for trust management, focusing on methodologies used to evaluate trust in MANETs.

Section 7: Trust Metrics for MANETs
Description 7: This section outlines different metrics used to measure trust in MANETs, distinguishing between social trust and QoS trust.

Section 8: Existing Trust Management in MANETs
Description 8: This section reviews various trust management schemes developed for purposes such as secure routing, authentication, intrusion detection, and access control.

Section 9: Trust Evidence Distribution and Evaluation
Description 9: This section discusses proposed frameworks for trust evidence distribution and evaluation in MANETs, highlighting significant models and schemes.

Section 10: Towards Trust-Based Cognitive MANETs
Description 10: This section proposes a trust management scheme based on social and cognitive network concepts and lists considerations for developers of MANET trust management schemes.

Section 11: Conclusion
Description 11: This section summarizes the paper’s insights on trust management in MANETs and suggests future research directions for developing adaptable, scalable, and reliable trust management schemes.