1. Panda: Public Auditing forShared Data withEfficient User Revocation inthe CloudBoyang Wang, Baochun Li, Member, IEEE, and Hui Li, Member, IEEE

2. AbstractWith data storage and sharing services in the cloud, users can easily modify and share data as a group.To ensure shared data integrity can be verified publicly, users in the group need to compute signatureson all the blocks in shared data. Different blocks in shared data are generally signed by different usersdue to data modifications performed by different users. For security reasons, once a user is revokedfrom the group, the blocks which were previously signed by this revoked user must be re-signed by anexisting user. The straightforward method, which allows an existing user to download thecorresponding part of shared data and re-sign it during user revocation, is inefficient due to the largesize of shared data in the cloud. In this paper, we propose a novel public auditing mechanism for theintegrity of shared data with efficient user revocation in mind. By utilizing the idea of proxy re-signatures,we allow the cloud to re-sign blocks on behalf of existing users during user revocation, sothat existing users do not need to download and re-sign blocks by themselves. In addition, a publicverifier is always able to audit the integrity of shared data without retrieving the entire data from thecloud, even if some part of shared data has been re-signed by the cloud. Moreover, our mechanism isable to support batch auditing by verifying multiple auditing tasks simultaneously. Experimental resultsshow that our mechanism can significantly improve the efficiency of user revocation. 3. Existing SystemAn existing system the file uploaded in cloud which not signed by user in each time ofupload. So that integrity of shared data is not possible in existing system. However,since the cloud is not in the same trusted domain with each user in the group,outsourcing every users private key to the cloud would introduce significant securityissue. 4. Disadvantages of Existing System For security reasons, when a user leaves the group or misbehaves, this user mustbe revoked from the group. As a result, this revoked user should no longer be ableto access and modify shared data, and the signatures generated by this revokeduser are no longer valid to the group. Since shared data is outsourced to the cloud and users no longer store it on localdevices, a straightforward method to re-compute these signatures during userrevocation. 5. Proposed SystemIn our Proposed system may lie to verifiers about the incorrectness of shared data inorder to save the reputation of its data services and avoid losing money on its dataservices. In addition, we also assume there is no collusion between the cloud and anyuser during the design of our mechanism. Generally, the incorrectness of share dataunder the above semi trusted model can be introduced by hardware/software failuresor human errors happened in the cloud. Considering these factors, users do not fullytrust the cloud with the integrity of shared data. 6. Advantages of Proposed System Blocking User account . Security question. Login with secret key in each time. 7. Architecture 8. ModulesUser Module:User module can divided into the following sub modules: Registration File Upload Download Re-upload UnblockAuditor Module:Auditor module can divided into the following sub modules: File Verification View FileAdmin Module:Admin module can divided into the following sub modules: View Files Block user 9. Module DescriptionUser Module Registration: In this module each user register his user details for using files. Onlyregistered user can able to login in cloud server . File Upload: In this module user upload a block of files in the cloud with encryptionby using his secret key. This ensure the files to be protected from unauthorizeduser. 10. Download: This module allows the user to download the file using his secret key to decrypt thedownloaded data of blocked user and verify the data and re-upload the block of file into cloud serverwith encryption .This ensure the files to be protected from unauthorized user. Re-upload: This module allow the user to re-upload the downloaded files of blocked userinto cloud server with resign the files (i.e) the files is uploaded with new signature like new secret withencryption to protected the data from unauthorized user. Unblock: This module allow the user to unblock his user account by answering his security questionregarding to answer that provided by his at the time of registration. Once the answer is matched to theanswer of registration time answer then only account will be unlocked. 11. Auditor Module File Verification: The public verifier is able to correctly check the integrity of shareddata. The public verifier can audit the integrity of shared data without retrieving theentire data from the cloud, even if some blocks in shared data have been re-signedby the cloud. Files View: In this module public auditor view the all details of upload, download,blocked user, re-upload. 12. Admin Module View Files: In this module public auditor view the all details of upload, download,blocked user, re-upload. Block User: In this module admin block the misbehave user account to protect theintegrity of shared data. 13. Minimum Hardware Configuration of theProposed System Processor : Intel/AMD Hard Disk : 40 GB Monitor : 14 Colour Monitor Mouse : Optical Mouse RAM : 512 MB 14. Software Configuration of the ProposedSystem Operating system : Windows 7 and above Coding Language : ASP.Net with C# Data Base : SQL Server 2008 15. References B. Wang, B. Li, and H. Li, Public Auditing for Shared Data with Efficient User Revoationin the Cloud, in the Proceedings of IEEE INFOCOM 2013, 2013, pp. 29042912. M. Armbrust, A. Fox, R. Griffith, A. D. Joseph, R. H. Katz, A. Konwinski, G. Lee, D. A.Patterson, A. Rabkin, I. Stoica, and M. Zaharia, A View of Cloud Computing,Communications of the ACM, vol. 53, no. 4, pp. 5058, Apirl 2010. G. Ateniese, R. Burns, R. Curtmola, J. Herring, L. Kissner, Z. Peterson, and D. Song,Provable Data Possession at Untrusted Stores, in the Proceedings of ACM CCS 2007,2007, pp. 598610. H. Shacham and B. Waters, Compact Proofs of Retrievability, in the Proceedings ofASIACRYPT 2008. Springer-Verlag,2008,pp. 90107. C. Wang, Q. Wang, K. Ren, and W. Lou, Ensuring Data Storage Security in CloudComputing, in the Proceedings of ACM/IEEE IWQoS 2009, 2009, pp. 19.