Provable Of Data Possession Scheme Based On Implicit Trusted Third Party

With the development of cloud storage,more and more companies and people get to know about and use it.But as the storage service providers are semi-trusted,the secrutiy of cloud storage has always been the focus of public concern,and the key driver for this industry.There are mainly three aspects in cloud storage security:confidentiality ensures that users' data is kept in cipertext in cloud and could only be accessed by authenticated users;integrity means users' cloud data identifies with the original one,not been deleted or distorted;availability means that authenticated users can access or retrieve their data.This paper mainly studies the remote data checking technique,Provable of Data Posession(PDP)scheme and improves the existing schemes in three aspects,data dynamic updates,introducing trusted third party in possession auditing on behalf of users and reducing the storage overheads of users,aiming to relieve users in all process of remote data integrity checking.We analyse the typical data update model in cloud storage,introduce auditing framework and improve the flow path of storing files,and come up with two more practical PDP schemes,MF-PDP and UP-PDP,remaining the security as well as reducing users'overheads.Finally,we implement our scheme in distributed cloud storage system.On data dynamic updates,we try to tackle the data dynamics problem of remote data checking for cloud storage from a different perspective.We define a new PDP model called Multiple-File PDP(MF-PDP)in accordance with the specific data update pattern for cloud storage.In contrast with existing PDP schemes that check the intactness of a single file(static or dynamic),a MF-PDP scheme checks the intactness of a dynamic file group consisting of a growing number of static files.By checking a group of files in one challenge,MF-PDP can sharply reduce the overhead of auditing.MF-PDP is more efficient than existing dynamic-supported schemes by not maintaining complex data structures.To address concerns about third-party auditing,we adopte a data possession auditing framework based on implicit TTPs,which are tamper-resistant hardware devices bundled with cloud servers that act as data possession auditors.The semi-trusted SSP interacts with the implicit TTP to produce tamper-evident logs,providing trustworthy audit results to users.In this manner,thirdparty auditing costs are reduced,and the risk of information leakage to auditors is minimized.To tackle the problem of large client's overhead,we propose a new flow path of storing files based on the assumption of economic rational Storage Services Providers(SSP),let SSP compute the authenticators of users' files.By integrating with RSA and PRF based homormophic authenticators,we implements two specific User-Free PDP(UF-PDP)schemes.The security of UF-PDP is garenteed by interaction protocols.To test the feasibility and performance of our scheme,we implemets MF-PDP and UF-PDP in distributed cloud storage system.Analytical results show that both MF-PDP and UF-PDP have reduce the complexity in auditing process from O(n)to O(1),what's more UF-PDP has reduced the overheads in storing process from O(n)to O(1).Experimental results demonstrate that MF-PDP reduces the overhead of auditing to less than 2 seconds regardless of the number of checked files,UF-PDP reduces the computational overheads of clients from 25479 seconds to 1 second when the file size is 1G.