Efficient Multiple Copy Integrity Auditing Scheme For Cloud Storage

Cloud computing is a new computing mode that based on shared resources and has developed rapidly in recent years.Cloud storage,as its core function,provides users with outsourced data storage service.However,while the local storage pressure on users is eliminated,users also lose the direct control over their data.Therefore,it is necessary to audit the integrity of remote data to ensure that the cloud server has stored the data correctly.The traditional integrity auditing schemes only consider storing single original file.In this case,once the cloud server fails or suffers malicious attacks,the file may be damaged and the loss of user is irreparable.In this thesis,two multi-copy integrity auditing schemes for cloud storage are proposed.While ensuring the availability of user's data,most operations are transferred from the auditor to the cloud server with the indistingushability obfuscation technique,which greatly eliminates the computation overhead of the auditor.The specific research results are as follows:1.For the cloud storage scenario of electronic health records,a multi-copy integrity auditing scheme PMCIA supporting privacy protection and batch auditing is proposed.In PMCIA,the patient only need to process the sensitive information in electronic health record,and a semi-trusted third party is responsible for the copy generation and outsourcing storage of electronic health record.In auditing phase,the semi-trusted third party generates an obfuscated auditing program based on in- distinguishable obfuscation technique,the cloud server generates integrity proof with this program.So that the auditor can verify the integrity of all copies at one time without performing pairing operation,which greatly improves the auditing efficiency.Besides,the thesis extends PMCIA to PMCIA-B,which supports batch auditing of multiple copies of multiple files,and the verification cost is independent of the number of files.2.For the multi-cloud server storage,a multi-copy integrity auditing scheme CDMCS supporting damaged copy location and data dynamics is proposed.In CDMCS,the user generates different ciphertext copies,and these copies are distributed to other cloud servers by the primary cloud server,thus reducing the communication overhead of the user in outsourcing storage.In auditing phase,the auditor only needs to interact with the primary cloud server to verify the integrity of all copies,binary search method and indistinguishability obfuscation can be used to locate damaged copy effectively.In addition,the scheme realizes data dynamics of all copies based on Merkle hash tree authentication structure.With aggregation signature algorithm,the update proofs of all cloud servers can be verified at one time,which greatly imprives the efficiency of verifying the update operations for the user.