The Public Audit For Dynamic Data In Cloud Storage

It is a light for big data that cloud storage. Its infinite storage space is critical for big data overflow. Cloud storage is beginning to apply to people’s life. But cloud storage isn’t also safe. Could it ensure the data privacy and data integrity when people save all data to cloud storage? This is a problem that needs to solve. The research purpose of the paper is to verify the data integrity in cloud storage by the third party, and to ensure not to reveal the data.The paper has two main tasks. One is to optimize the audit protocol based on Wang’s, and the protocol uses RSA digital signature and homomorphism authentication instead of the billinear pairings, which greatly improves operation efficiency, reduces communication cost and elapsed time. The paper is to verify the data integrity and security for single or multiple users, and to describe the Merkle Hash Tree generation and validation principles for the dynamic data. The other is to expand a single copy audit to multiple copies audit, which can verify the user data integrity and ensure the data recoverability. The scheme can ensure to find or recover the data when an untrusted cloud storage loses, deletes or updates the data.The protocol optimizes the operation in response and verification phase by reducing exponential calculation and billinear pairings calculation. Protecting user data is based on hash function’s unilateral directivity to realize. The paper is to send the hash value to the third party, and the third party couldn’t get the data from the hash value. The paper has compared with Wang’s protocol by experiments and gotten the experimental results to prove.The protocol is more secure than Wang’s. When user updates data, signature in Wang’s is easy to forge, but the protocol suggested by the paper could solve the problem. The signature includes the data, and the protocol can avoid to use other data instead of lost data to verify.