Jin-Hee Cho

Dynamic Trust Management for Delay Tolerant Networks and Its Application to Secure Routing

Delay tolerant networks (DTNs) are characterized by high end-to-end latency, frequent disconnection, and opportunistic communication over unreliable wireless links. In this paper, we design and validate a dynamic trust management protocol for secure routing optimization in DTN environments in the presence of well-behaved, selfish and malicious nodes. We develop a novel model-based methodology for the analysis of our trust protocol and validate it via extensive simulation. Moreover, we address dynamic trust management, i.e., determining and applying the best operational settings at runtime in response to dynamically changing network conditions to minimize trust bias and to maximize the routing application performance. We perform a comparative analysis of our proposed routing protocol against Bayesian trust-based and non-trust based (PROPHET and epidemic) routing protocols. The results demonstrate that our protocol is able to deal with selfish behaviors and is resilient against trust-related attacks. Furthermore, our trust-based routing protocol can effectively trade off message overhead and message delay for a significant gain in delivery ratio. Our trust-based routing protocol operating under identified best settings outperforms Bayesian trust-based routing and PROPHET, and approaches the ideal performance of epidemic routing in delivery ratio and message delay without incurring high message or protocol maintenance overhead.

Modeling and analysis of trust management with trust chain optimization in mobile ad hoc networks

We develop and analyze a trust management protocol for mission-driven group communication systems in mobile ad hoc networks using hierarchical modeling techniques based on stochastic Petri nets. Trust among mobile nodes is crucial for team collaborations with new coalition partners without prior interactions for mission-driven group communication systems in battlefield situations. In addition, ensuring a certain level of trust is also critical for successful mission completion. Our work seeks to identify the optimal length of a trust chain among peers in a trust web that generates the most accurate trust levels without revealing risk based on a tradeoff between trust availability and path reliability over trust space. We define a trust metric for mission-driven group communication systems in mobile ad hoc networks to properly reflect unique characteristics of trust concepts and demonstrate that an optimal trust chain length exists for generating the most accurate trust levels for trust-based collaboration among peers in mobile ad hoc networks while meeting trust availability and path reliability requirements.

Trust Management for Encounter-Based Routing in Delay Tolerant Networks

We propose and analyze a class of trust management protocols for encounter-based routing in delay tolerant networks (DTNs). The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only quality-of-service (QoS) trust properties (connectivity) but also social trust properties (honesty and unselfishness) to evaluate other nodes encountered. Two versions of trust management protocols are considered: an equal-weight QoS and social trust management protocol (called trust-based routing) and a QoS only trust management protocol (called connectivity-based routing). By utilizing a stochastic Petri net model describing a DTN behavior, we analyze the performance characteristics of these two routing protocols in terms of message delivery ratio, latency, and message overhead. We also perform a comparative performance analysis with epidemic routing for a DTN consisting of heterogeneous mobile nodes with vastly different social and networking behaviors. The results indicate that trust-based routing approaches the ideal performance of epidemic routing in delivery ratio, while connectivity-based routing approaches the ideal performance in message delay of epidemic routing, especially as the percentage of selfish and malicious nodes present in the DTN system increases. By properly selecting weights associated with QoS and social trust metrics for trust evaluation, our trust management protocols can approximate the ideal performance obtainable by epidemic routing in delivery ratio and message delay without incurring high message overhead.

Effect of Intrusion Detection on Reliability of Mission-Oriented Mobile Group Systems in Mobile Ad Hoc Networks

For mission-oriented mobile group systems designed to continue mission execution in hostile environments in the presence of security attacks, it is critical to properly deploy intrusion detection techniques to cope with insider attacks to enhance the system reliability. In this paper, we analyze the effect of intrusion detection system (IDS) techniques on the reliability of a mission-oriented group communication system consisting of mobile groups set out for mission execution in mobile ad hoc networks. Unlike the common belief that IDS should be executed as often as possible to cope with insider attacks to prolong the system lifetime, we discover that IDS should be executed at an optimal rate to maximize the mean time to failure of the system. Further, the optimal rate at which IDS is executed depends on the operational conditions, system failure definitions, attacker behaviors, and IDS techniques used. We develop mathematical models based on Stochastic Petri nets to identify the optimal rate for IDS execution to maximize the mean time to failure of the system, when given a set of parameter values characterizing the operational conditions, and attacker behaviors.

A Survey on Trust Modeling

The concept of trust and/or trust management has received considerable attention in engineering research communities as trust is perceived as the basis for decision making in many contexts and the motivation for maintaining long-term relationships based on cooperation and collaboration. Even if substantial research effort has been dedicated to addressing trust-based mechanisms or trust metrics (or computation) in diverse contexts, prior work has not clearly solved the issue of how to model and quantify trust with sufficient detail and context-based adequateness. The issue of trust quantification has become more complicated as we have the need to derive trust from complex, composite networks that may involve four distinct layers of communication protocols, information exchange, social interactions, and cognitive motivations. In addition, the diverse application domains require different aspects of trust for decision making such as emotional, logical, and relational trust. This survey aims to outline the foundations of trust models for applications in these contexts in terms of the concept of trust, trust assessment, trust constructs, trust scales, trust properties, trust formulation, and applications of trust. We discuss how different components of trust can be mapped to different layers of a complex, composite network; applicability of trust metrics and models; research challenges; and future work directions.

Trust management in mobile ad hoc networks for bias minimization and application performance maximization

Abstract Trust management for mobile ad hoc networks (MANETs) has emerged as an active research area as evidenced by the proliferation of trust/reputation protocols to support mobile group based applications in recent years. In this paper we address the performance issue of trust management protocol design for MANETs in two important areas: trust bias minimization and application performance maximization. By means of a novel model-based approach to model the ground truth status of mobile nodes in MANETs as the basis for design validation, we identify and validate the best trust protocol settings under which trust bias is minimized and application performance is maximized. We demonstrate the effectiveness of our approach with an integrated social and quality-of-service (QoS) trust protocol (called SQTrust) with which we identify the best trust aggregation setting under which trust bias is minimized despite the presence of malicious nodes performing slandering attacks. Furthermore, using a mission-oriented mobile group utilizing SQTrust, we identity the best trust formation protocol setting under which the application performance in terms of the system reliability of the mission-oriented mobile group is maximized.

Composite trust-based public key management in mobile ad hoc networks

Public key management in mobile ad hoc networks (MANETs) has been studied for several decades. Yet no single solution has completely resolved well known design challenges resulting from the unique characteristics of MANETs. These challenges include no centralized trusted entities, resource constraints, and high security vulnerabilities. This work proposes a fully distributed trust-based public key management approach for MANETs using a soft security mechanism based on the concept of trust. Instead of using hard security approaches, as in traditional security techniques, to eliminate security vulnerabilities, our work aims to maximize performance by trading off risk (i.e., security vulnerability) for trust. In this work, we propose a composite trust-based public key management (CTPKM) with no centralized trust entity with the goal of maximizing performance (e.g., service availability or efficiency) while mitigating security vulnerability. Each node employs a trust threshold to determine whether or not to trust another node. Each nodes decision making using the given trust threshold affects performance and security of CTPKM. Our simulation experimental results show that there exists an optimal trust threshold that can best balance and meet the conflicting goals between performance and security, exploiting the inherent tradeoff between trust and risk.

Performance analysis of hierarchical group key management integrated with adaptive intrusion detection in mobile ad hoc networks

We develop a mathematical model to quantitatively analyze a scalable region-based hierarchical group key management protocol integrated with intrusion detection to deal with both outsider and insider security attacks for group communication systems (GCSs) in mobile ad hoc networks (MANETs). Our proposed adaptive intrusion detection technique is based on majority voting by nodes in a geographical region to cope with collusion of compromised nodes, with each node preloaded with anomaly-based or misuse-based intrusion detection techniques to diagnose compromised nodes in the same region. When given a set of parameter values characterizing operational and environmental conditions, we identify the optimal intrusion detection rate and the optimal regional area size under which the mean time to security failure of the system is maximized and/or the total communication cost is minimized for GCSs in MANET environments. The tradeoff analysis in performance versus security is useful in identifying and dynamically applying optimal settings to maximize the system lifetime for scalable mobile group applications while satisfying application-specific performance requirements.

On the tradeoff between altruism and selfishness in MANET trust management

Mobile ad hoc and sensor networks may consist of a mixture of nodes, some of which may be considered selfish due to a lack of cooperativeness in providing network services such as forwarding packets. In the literature, existing trust management protocols for mobile ad hoc networks advocate isolating selfish nodes as soon as they are detected. Further, altruistic behaviors are encouraged with incentive mechanisms. In this paper, we propose and analyze a trust management protocol for group communication systems where selfish nodes exist and system survivability is highly critical to mission execution. Rather than always encouraging altruistic behaviors, we consider the tradeoff between a nodes individual welfare (e.g., saving energy to prolong the node lifetime) vs. global welfare (e.g., achieving a given mission with sufficient service availability) and identify the best design condition of this behavior model to balance selfish vs. altruistic behaviors. With the system lifetime and the mission success probability as our trust-based reliability metric, we show that our behavior model that exploits the tradeoff between selfishness vs. altruism outperforms one that only encourages altruistic behaviors.

Integrated Social and QoS Trust-Based Routing in Delay Tolerant Networks

We propose and analyze a class of integrated social and quality of service (QoS) trust-based routing protocols in mobile ad-hoc delay tolerant networks. The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only QoS trust properties but also social trust properties to evaluate other nodes encountered. We prove that our protocol is resilient against bad-mouthing, good-mouthing and whitewashing attacks performed by malicious nodes. By utilizing a stochastic Petri net model describing a delay tolerant network consisting of heterogeneous mobile nodes with vastly different social and networking behaviors, we analyze the performance characteristics of trust-based routing protocols in terms of message delivery ratio, message delay, and message overhead against connectivity-based, epidemic and PROPHET routing protocols. The results indicate that our trust-based routing protocols outperform PROPHET and can approach the ideal performance obtainable by epidemic routing in delivery ratio and message delay, without incurring high message overhead. Further, integrated social and QoS trust-based protocols can effectively trade off message delay for a significant gain in message delivery ratio and message overhead over traditional connectivity-based routing protocols.