Aiming at overcoming problems such as malicious entities and trust crises in cloud environments, a trust management model based on mutual trust and a rewardwith-punishment mechanism is proposed in this paper. First, according to reputation values of entities and trust relationships among entities, we calculate the comprehensive trust values of a service request user to several candidate service providers and probe these providers with high comprehensive trust values. Second, we select a trade provider according to mutual trust. Finally, after the trade, we update the reputation values and other data of the request user, trade provider, and recommenders based on the final trade result to reward or punish them to various degrees, thus ultimately reducing malicious or dishonest behavior. The experimental results show that our model can effectively identify malicious entities to increase the trade success rate.
K E Y W O R D Scloud environment, mutual trust, reputation, reward-with-punishment
INTRODUCTIONCloud computing is a new network application model that was proposed by Google in 2006. Cloud computing was developed based on a series of traditional technologies, such as grid computing, distributed systems, peer to peer (P2P), and virtualization. It is a new information technology service resource. It distributes computing tasks over a resource pool that is composed of many computers, thereby enabling various application systems to obtain computing power, storage space, and information services as needed and providing dynamically scalable and cheap computing services on demand through the network. 1,2 Cloud computing can be divided into the following three categories according to the service model: IaaS (infrastructure as a service), PaaS (platform as a service), and SaaS (software as a service). 3 However, the widespread application of cloud computing technology also faces many security threats, such as privacy theft, resource misappropriation, virus attacks, and user malicious behavior attacks. The cloud environment is open, and users can add, delete, modify, and check data through the network. If users who passed the identity authentication behave maliciously, a major challenge will be posed to cloud computing security. Therefore, each user's behavior must be evaluated to identify the malicious users.In addition, there is a crisis of trust between cloud service providers and users: Users have doubts regarding whether cloud service providers can provide qualified cloud services in trade (in this paper, when a user buys and uses a provider's service, we say there is a εtradeε between the user and the provider, and the provider is called the trade provider.), while providers also have doubts about users. Therefore, to ensure the smooth operation of trades, the trust relationship between users and providers must be evaluated. Although researchers have proposed various trust models, most models consider only the attitude of user in the trade and ignore that of provider, or do not consider the impact of trade prices ...