Cloud storage is one of the service provided by Cloud computing in which data is maintained, managed, backed up remotely and made available to users over a network (typically the Internet). The user is concerned about the integrity of data stored in the cloud as the user's data can be attacked or modified by outside attacker. Therefore, a new concept called data auditing is introduced which check the integrity of data with the help of an entity called Third Party Auditor (TPA). The purpose of this work is to develop an auditing scheme which is secure, efficient to use and possess the capabilities such as privacy preserving, public auditing, maintaining the data integrity along with confidentiality. Thus the new auditing scheme has been developed by considering all these requirements. It consist of three entities: data owner, TPA and cloud server. The data owner performs various operations such as splitting the file to blocks, encrypting them, generating a hash value for each, concatenating it and generating a signature on it. The TPA performs the main role of data integrity check. It performs activities like generating hash value for encrypted blocks received from cloud server, concatenating them and generates signature on it. It later compares both the signatures to verify whether the data stored on cloud is tampered or not. It verifies the integrity of data on demand of the users. Thus no additional burden is provided on the cloud server. It is used only to save the encrypted blocks of data. All the task for the scheme is performed by the TPA and data owner. This proposed auditing scheme make use of AES algorithm for encryption, SHA-2 for integrity check and RSA signature for digital signature calculation.

1. S Ezhil Arasu, B Gowri, and S Ananthi. Privacy-Preserving Public Auditing in cloud using HMAC Algorithm. International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277, 3878, 2013.
2. IK Meenakshi and Sudha George. Cloud Server Storage Security using TPA. International Journal of Advanced Research in Computer Science & Technology (IJARCST) ISSN: 2347-9817, 2014.
3. Jadhav Santosh and B. R nandwalkar. Privacy Preserving and Batch auditing in Secure Cloud Data Storage using AES. Proceedings of 13th IRF International Conference, ISBN: 978-93-84209-37-72014.
4. Zissis, Dimitrios, and Dimitrios Lekkas. Addressing cloud computing security issues. Future Generation computer systems 28. 3 (2012): 583-592.
5. Tejaswini, K. Sunitha, and S. K. Prashanth. Privacy Preserving and Public Auditing Service for Data Storage in Cloud Computing. Indian Journal of Research PARIPEX, 2(2), 2013.
6. Cong Wang, Sherman SM Chow, Qian Wang, Kui Ren, and Wenjing Lou. Privacy Preserving Public Auditing for Secure Cloud Storage. http://eprint. iacr. org/2009/579. pdf
7. Cong Wang, Sherman SM Chow, Qian Wang, Kui Ren, and Wenjing Lou. Privacy Preserving Public Auditing for Secure Cloud Storage. Computers, IEEE Transactions on, 62(2):362–375, 2013.
8. Cong Wang, Qian Wang, Kui Ren, Ning Cao, and Wenjing Lou. Toward secure and dependable storage services in cloud computing. Services Computing, IEEE Transactions on, 5(2):220–232, 2012.
9. Cong Wang, Qian Wang, Kui Ren, and Wenjing Lou. Privacy-Preserving Public Auditing for Data Storage Security in Cloud Computing. In INFOCOM, 2010 Proceedings IEEE, pages 1–9. IEEE, 2010.
10. Qian Wang, Cong Wang, Kui Ren, Wenjing Lou, and Jin Li. Enabling Public Auditability and Data Dynamics for Storage Security in Cloud Computing. Parallel and Distributed Systems, IEEE Transactions on, 22(5):847–859, 2011.
11. Solomon GuadieWorku, Chunxiang Xu, Jining Zhao, and Xiaohu He. Secure and efficient privacy-preserving public auditing scheme for cloud storage. Computers & Electrical Engineering, 40(5):1703–1713, 2014.
12. Mell, Peter, and Tim Grance. The NIST definition of cloud computing. (2011).
13. Ritu Tripathi and Sanjay Agrawal. Comparative study of symmetric and asymmetric cryptography techniques. International Journal of Advance Foundation and Research in Computer (IJAFRC), 2014.
14. Understanding Cryptography: A textbook for Students and Practitioners, Christof Paar, ?Jan Pelzl

Cloud Storage Tpa Privacy Preserving Public Auditing Integrity