Research On Privacy-preserving Cloud Chain Service And Audit Technology

Cloud chain service emerged as a new service model.Cloud service providers utilize their cloud computing to provide users with cloud chain services,including deploying blockchains and maintaining blockchain networks.By obtaining cloud chain services,enterprises and users can quickly establish a cloud chain and use cloud chain resources.Due to the limited storage and computing capabilities of the cloud chain,the cloud chain service of data storage is divided into on-chain storage mode and off-chain storage mode.Although the data stored on-chain cannot be tampered with,data security,searching,and sharing on the chain have become issues.In the off-chain storage mode,data is stored in the cloud server at the bottom of the cloud chain,and users can use cloud computing resources to complete their computing needs,but the security of off-chain data storage and computing process becomes a problem.In addition,cloud chain services may have bad quality,resulting in compensation disputes between users and service providers.The audit results of the existing audit schemes are not credible,and privacy is leaked during the audit process.Therefore,the research contents of this paper are as follows:(1)For the on-chain storage mode in the cloud chain service,an attribute searchable encryption-based cloud chain data privacy-preserving scheme is designed.The private cloud chain and the public cloud chain are used for collaborative storage,the ciphertext of files is stored in the private cloud chain,and the ciphertext of keywords is stored in the public cloud chain to ensure the security of data files and implement fine-grained access control.Then,we design a miner selection algorithm to select high-quality witness nodes to help users efficiently complete on-chain retrieval tasks and obtain ciphertext files.Moreover,trusted retrieval can be achieved by recording retrieval behavior on the chain.(2)For the off-chain storage mode in the cloud chain service,an off-chain data privacy-preserving scheme based on homomorphic encryption is designed.The data in the off-chain cloud server is encrypted to ensure data security,and the data hash value is stored on the chain to ensure that the data cannot be tampered with.A smart contracts-based access control strategy is designed to automatically verify the access rights and data processing rights of a user,and realize multi-party data security computing without revealing the privacy data of a user.Through security analysis and performance analysis,the effectiveness of the above schemes is verified.(3)For the problems of untrustworthy audit results and privacy leakage in the audit process of cloud chain service,we design a smart contracts-based cloud chain service quality audit model.By making cloud chain service level agreements,various service attribute standards are specified.The dual monitoring scheme of users and service providers is adopted to ensure the authenticity of data,and the TORE encryption algorithm is used to securely store monitoring service parameters on the chain.We design CSLA audit smart contracts to automatically conduct privacy audits of ciphertext parameters to determine whether the cloud chain service meets the standards or not.Finally,we design a penalty mechanism for violations and conduct reputation management to motivate service providers to provide quality services.The overhead of the audit system is evaluated by experiments,moreover,the security and the effectiveness of the scheme are verified.