Electronic markets, distributed peer-to-peer applications and other forms of online collaboration are all based on mutual trust, which enables transacting peers to overcome the uncertainty and risk inherent in the environment. Reputation systems provide essential input for computational trust as predictions on future behaviour based on the past actions of a peer. In order to analyze the maturity of current reputation systems, we compare eleven reputation systems within a taxonomy of the credibility aspects of a reputation system. The taxonomy covers three topics: 1) the creation and content of a recommendation, 2) the selection and use of recommenders, and 3) the interpretation and reasoning applied to the gathered information. Although we find it possible to form a trusted reputation management network over an open network environment, there are still many regulatory and technical obstacles to address. This survey reveals various good mechanisms and methods used, but the area still requires both a) formation of standard mechanisms and metrics for reputation system collaboration and b) standard metainformation of right granularity for evaluating the credibility of reputation information provided.

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Despite the steady growth of e-commerce communities in the past two decades, little has changed in the way these communities manage reputation for building trust and for protecting their member's financial interests against fraud. As these communities mature and the defects of their reputation systems are revealed, further potential for deception against their members is created, that pushes the need for novel reputation mechanisms. Although a high volume of research works has explored the concepts of reputation and trust in e-communities, most of the proposed reputation systems target decentralized e-communities, focusing on issues related with the decentralized reputation management; they have not thus been integrated in e-commerce platforms. This work's objective is to provide an attackresilient feedback-based reputation system for modern e-commerce platforms, while minimizing the incurred financial burden of potent security schemes. Initially, we discuss a series of attacks and issues in reputation systems and study the different approaches of these problems from related works, while also considering the structural properties, defense mechanisms and policies of existing platforms. Then we present our proposition for a robust reputation system which consists of a novel reputation metric and attack prevention mechanisms. Finally, we describe the simulation framework and tool that we have implemented for thoroughly testing and evaluating the metric's resilience against attacks and present the evaluation experiments and their results. We consider the presented simulation framework as the second contribution of our article, aiming at facilitating the simulation and elaborate evaluation of reputation systems which specifically target e-commerce platforms by thoroughly presenting it, exhibiting its usage and making it available to the research community.

Various reputation systems have been proposed for a broad range of distributed applications, such as peer-to-peer, ad-hoc, and multiagent systems. Their evaluation has been mostly based on proprietary methods due to the lack of widely acceptable evaluation measures and methodologies. Differentiating factors in various evaluation approaches include the evaluation metrics, the consideration of the dynamic behavior of peers, the use of social networks, or the study of resilience to specific threat scenarios. The lack of a generally accepted common evaluation framework hinders the objective evaluation and comparison of different reputation systems. Aiming at narrowing the gap in the research area of objective evaluation of reputation systems, in this article, we study the various approaches to evaluating and comparing reputation systems, present them in a taxonomy, and analyze their strengths and limitations, with special focus on works suggesting a Common Evaluation Framework (CEF). We identify the challenges for a widely accepted CEF that enables testing and benchmarking of reputation systems, and we present the required properties for such a CEF; we also present an analysis of current CEF-related works in the context of the identified properties and our related proposals.