Cooperative Intelligent Transportation Systems, mainly represented by vehicular ad hoc networks (VANETs), are among the key components contributing to the Smart City and Smart World paradigms. Based on the continuous exchange of both periodic and event triggered messages, smart vehicles can enhance road safety, while also providing support for comfort applications. In addition to the different communication protocols, securing such communications and establishing a certain trustiness among vehicles are among the main challenges to address, since the presence of dishonest peers can lead to unwanted situations. To this end, existing security solutions are typically divided into two main categories, cryptography and trust, where trust appeared as a complement to cryptography on some specific adversary models and environments where the latter was not enough to mitigate all possible attacks. In this paper, we provide an adversary-oriented survey of the existing trust models for VANETs. We also show when trust is preferable to cryptography, and the opposite. In addition, we show how trust models are usually evaluated in VANET contexts, and finally, we point out some critical scenarios that existing trust models cannot handle, together with some possible solutions.

Trust Management for Vehicular Networks: An Adversary-Oriented Overview

The basis of vehicular ad hoc networks (VANETs) is the exchange of data between entities, and making a decision on received data/event is usually based on information provided by other entities. Many researchers utilize the concept of trust to assess the trustworthiness of the received data. Nevertheless, the lack of a review to sum up the best available research on specific questions on trust management in vehicular ad hoc networks is sensible. This paper presents a systematic literature review to provide comprehensive and unbiased information about various current trust conceptions, proposals, problems, and solutions in VANETs to increase quality of data in transportation. For the purpose of the writing of this paper, a total of 111 articles related to the trust model in VANETs published between 2005 and 2014 were extracted from the most relevant scientific sources (IEEE Computer Society, ACM Digital Library, Springer Link, Science Direct, and Wiley Online Library). Finally, ten articles were eventually analyzed due to several reasons such as relevancy and comprehensiveness of discussion presented in the articles. Using the systematic method of review, this paper succeeds to reveal the main challenges and requirements for trust in VANETs and future research within this scope.

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Trust management in vehicular ad hoc network: a systematic review

BTRES: Beta-based Trust and Reputation Evaluation System for Wireless Sensor Networks

Security of vehicular ad-hoc networks: A comprehensive survey

The extremely vibrant, scattered, and non–transparent nature of cloud computing formulate trust management a significant challenge. According to scholars the trust and security are the two issues that are in the topmost obstacles for adopting cloud computing. Also, SLA (Service Level Agreement) alone is not necessary to build trust between cloud because of vague and unpredictable clauses. Getting feedback from the consumers is the best way to know the trustworthiness of the cloud services, which will help them improve in the future. Several researchers have stated the necessity of building a robust management system and suggested many ideas to manage trust based on consumers' feedback. This paper has reviewed various reputation-based trust management systems, including trust management in cloud computing, peer-to-peer system, and Adhoc system.

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A Review on Various Applications of Reputation Based Trust Management

Vehicular ad hoc network (VANET) is a promising technology for providing safer roads and a more efficient driving experience. However, the deployment of VANETs is dependent on several issues in security and privacy. In this paper, a trust-based privacy-preserving model for VANETs is presented. The model is unique in its ability to protect privacy while maintaining accurate reputation-based trust. We use the notion of groups in order to make the VANET users anonymous within their groups and yet identifiable and accountable to their group managers. The use of groups simplifies the task of building reputation and calculating trust in the received messages in order to provide better and more confident decisions. We present simulations of the proposed model that verify its correctness and reliability.

A Privacy-Preserving Trust Model for VANETs

We present PATROL-F (comPrehensive reputAtion-based TRust mOdeL with Fuzzy subsystems) as a comprehensive model for reputation-based trust incorporating fuzzy subsystems to protect interacting hosts in distributed systems. PATROL-F is the fuzzy version of our previous model PATROL, and aims at achieving a truly unique model incorporating various concepts that are important for the calculation of reputation values and the corresponding decisions of whether or not to trust. Among the incorporated concepts are direct experiences and reputation values, the credibility of a host to give recommendations, the decay of information with time based on a dynamic decay factor, first impressions, and a hierarchy of host systems. The model also implements the concepts of similarity, popularity, activity, and cooperation among hosts. In addition, PATROL-F's fuzzy subsystems account for humanistic and subjective concepts such as the importance of a transaction, the decision in the uncertainty region, and setting the result of interaction. We present simulations of PATROL-F and show its correctness and reliability.

Original research paper: Fuzzy reputation-based trust model

In this paper, we present CENTERA, a CENtralized Trust-based Efficient Routing protocol with an appropriate authentication scheme for wireless sensor networks (WSN). CENTERA utilizes the more powerful base station (BS) to gather minimal neighbor trust information from nodes and calculate the best routes after isolating different types of “bad” nodes. By periodically accumulating these simple local observations and approximating the nodes' battery lives, the BS draws a global view of the network, calculates three quality metrics—maliciousness, cooperation, and compatibility—and evaluates the Data Trust and Forwarding Trust values of each node. Based on these metrics, the BS isolates “bad”, “misbehaving” or malicious nodes for a certain period, and put some nodes on probation. CENTERA increases the node's bad/probation level with repeated “bad” behavior, and decreases it otherwise. Then it uses a very efficient method to distribute the routing information to “good” nodes. Based on its target environment, and if required, CENTERA uses an authentication scheme suitable for severely constrained nodes, ranging from the symmetric RC5 for safe environments under close administration, to pairing-based cryptography (PBC) for hostile environments with a strong attacker model. We simulate CENTERA using TOSSIM and verify its correctness and show some energy calculations.

CENTERA: A Centralized Trust-Based Efficient Routing Protocol with Authentication for Wireless Sensor Networks

In this paper, we present PATROL, a general and comprehensive reputation-based trust model for distributed computing. The proposed model is an enhancement over our previous model, TRUMMAR, and aims at achieving a truly unique model that incorporates most concepts that are essential to determining trust-based decisions. Among the concepts upon which the trust model is based are reputation values, direct experiences, trust in the credibility of a host to give recommendations, decay of information with time based on a dynamic decay factor, first impressions, similarity, popularity, activity, cooperation between hosts, in addition to a hierarchy of host systems. The simulations performed on this model confirm its correctness and its adaptability to different environments and situations.

PATROL: a comprehensive reputation-based trust model

In this paper, we present CENTER, a CENtralized Trust-based Efficient Routing protocol for wireless sensor networks (WSN). CENTER is a secure and efficient routing protocol that utilizes the powerful sink base station (BS) to identify and ban different types of misbehaving nodes that may interrupt or abuse the functionality of the WSN. In CENTER, the BS periodically accumulates simple local observations of every node and deduces a detailed global view of the network. The BS calculates different quality metrics - namely the maliciousness, cooperation, and compatibility, approximates the battery life, and evaluates the Data Trust and Forwarding Trust values of each node. The BS then uses an effective technique to isolate all “bad” nodes, whether misbehaving or malicious, based on their history. Finally, the BS uses an efficient method to disseminate updated routing information, indicating the uplinks and the next hop downlink for every node. Through its centralized approach, CENTER provides more efficient and secure routing while accounting for the energy-constrained sensor nodes. We present simulation results of CENTER performed using TOSSIM to verify its correctness, security, and reliability.

Ayman Tajeddine

Papers

A Privacy-Preserving Trust Model for VANETs

Original research paper: Fuzzy reputation-based trust model

CENTERA: A Centralized Trust-Based Efficient Routing Protocol with Authentication for Wireless Sensor Networks

PATROL: a comprehensive reputation-based trust model

CENTER: A Centralized Trust-Based Efficient Routing protocol for wireless sensor networks