Abstract: Cloud Computing is that the new buzz word in todayís computing world. though there's large buzz, many of us are confused on specifically what cloud computing is, particularly the term is used to mean nearly anything. Cloud Computing has been visualised because the next generation design of IT Enterprise. It moves the application software and databases to the centralized massive data centres, wherever the management of the data and services might not be absolutely trustworthy. This distinctive paradigm brings concerning several new security challenges, that haven't been well understood. This work studies the problem of ensuring the integrity of data storage in Cloud Computing. Especially, we think about the task of permitting a third party auditor (TPA), on behalf of the cloud client, to verify the integrity of the dynamic data kept within the cloud. To securely introduce an efficient third party auditor (TPA), the subsequent two basic necessities should be met. First, TPA should be able to efficiently audit the cloud data storage without demanding the native copy of data, and introduce no extra on-line burden to the cloud user. Second, the third party auditing method should bring in no new vulnerabilities towards user data privacy. During this paper, we utilize and uniquely combine the general public key primarily based homomorphic authenticator with random masking to realize the privacy-preserving public cloud data auditing system, which meets all above needs. to deal with these issues, our work utilizes the technique of secret key primarily based bilaterally symmetrical key cryptography that enables TPA to perform the auditing without demanding the native copy of userís keep data and therefore severely deduces the transmission and computation overhead as compared to the simple data auditing approaches. The projected system offer safer design by using light weighted APCC (Authentication protocol for cloud computing).In previous system SSL is employed for this purpose. Than challenge handshake authentication protocol is employed for authentication. Challenge handshake authentication protocol is employed for authentication once client request for any data or service on the cloud .We will use VerifyProof run by TPA to audit the proof from the cloud. Initially request sends for identity of client by Service supplier authenticator. For sending or receiving data over cloud we are going to use blowfish for security purpose.

Keywords: Cloud computing, Cloud, TPA, Cryptography, Blowfish, symmetric key.