A Trust Evaluation Model for Cloud Computing

1. Introduction

Cloud computing is an emerging information technology that changes the way IT architectural solutions. It is a new pattern of business computing, and it can dynamically provide computing services supported by state-of-the-art data centers that usually employ Virtual Machine (VM) technologies. One of the most critical issues in cloud computing is security.

The trust mechanism provides a good way for improving the system security. It is a new and emerging security mode to provide security states, access control, reliability and policies for decision making by identifying and distributing the malicious entities based on converting and extracting the detected results from security mechanisms in different systems and collecting feedback assessments continually. In recent years, many scholars have made a lot of research on trust model. Hwang et al. assessed the security demands of three cloud service models: IaaS, PaaS and SaaS. Integrated cloud architecture was presented to reinforce the security and privacy in cloud applications. Some security protection mechanisms were suggested, such as finegain access control, trust delegation and negotiation, reputation system of resource sites. Zissis et al. pointed out that security in a cloud environment requires a systemic point of view, from which security will be constructed on trust, mitigating protection to a trusted third party. Takabi et al. illustrated the unique issues of cloud computing that exacerbate security and privacy challenges in clouds. Various approaches to address these challenges were discussed. It explores the future work needed to provide a trustworthy cloud computing environment. Tian et al. put forward basic criteria about evaluating node behavior trust and evaluation strategy in the cloud computing. Based on the basic criteria of the evaluation, the sliding window was used to carry out the evaluation of node behavior trust. Then a kind of evaluation mechanism on node behavior trust based on sliding windows model was brought forward. Jiang et al. proposed a new evidential trust model for open distributed systems. This model was based on an improved D-S evidence theory by the introduction of time efficiency factor calculation function and the modification of D-S combination rules. It is highly effective in defending attacks on the system for malicious behaviors.

In this paper, we propose a trust evaluation model based on D-S evidence theory and sliding windows to evaluate the credibility of entities and detect the malicious entities for cloud computing. In our model, direct interactions among entities are regard as first-hand evidences. We evaluate the timeliness of the interaction evidence by means of sliding windows. Trust computing of entities is based on D-S theory with the help of the interaction evidences. Recommendation trust values from different entities are regard as second-hand evidences. The combination of the recommendation trust values forms the reputation of entities. Finally, experiments were carried out to estimate the effectiveness and the anti-attack of the proposed model.

The remainder of this paper is organized as follows. Section 2 describes the proposed trust evaluation model. In section 3, the experimental results are shown and discussed. Finally, section 4 provides the conclusion and mentions our future research directions.