Abstract
Distributed cloud storage (DCS) has been undergoing fast development to provide customers with multiple storage resources in a mix of locations and environments that best meet the service and performance requirements. Trust is widely regarded as one of the top obstacles to the adoption and growth of DCS. Nonetheless, the existing works did not take the storage resource capacity of cloud service providers (CSPs) into the reputation evaluation, and most rely on a centralized reputation management framework. We bridge this gap by proposing a blockchain-assisted reputation mechanism for DCS. First, a blockchain-assisted DCS model is proposed to ensure the traceability and tamper proof of reputation-related data. Second, we propose a service credibility quantification method based on rating screening to mitigate the impact of outliers. Third, we design a stochastic process to characterize the storage resource change to quantify CSPs survival probability. Finally, we derive a reputation calculation algorithm based on the above two metrics that protects the authenticity of CSPs' reputations in the presence of attacks. The security analysis and simulation results show that the proposed mechanism is reliable and effective in promoting the service success rate and improving the efficiency and security of the service of DCS.