An efficient data integrity & data recovery with two TPAs in cloud data storage

Cloud Computing has gained popularity in recent years. Cloud provides huge storage space for various types of data and can provide unlimited computing resources on demand. These cloud services are accessed by users at any time and from anywhere, also user can store or retrieve their files or data as well. However data outsourcing model in cloud is one of the biggest security issue. Frequent integrity checking is needed to keep an eye on data. Merkle Hash Tree (MHT), SHA-512, AES algorithm is used in our proposed system to maintain data integrity at the untrusted server. In most of the existing systems, RSA algorithm was used for storage security. AES algorithm is faster in encryption and decryption and the storage space requirement being less as compared to RSA, thus we improve the performance by making use of AES algorithm. It is not possible for users to keep eye on data of cloud server. Thus to keep client/user free from the burden of data integrity checking, we introduce an entity called the Third Party Auditor (TPA), which acts on behalf of client for data integrity checking and send an alert to notify the status of the stored data. In this paper we use two TPAs. Thus if main TPA goes offline secondary TPA will take care of it. Proposed storage security scheme also assures recovery of data, in case of data loss or corruption, by providing a recovery system. Thus the proposed Project aims to maintain the correctness of user data and support recovery of user data or files. The system also reduces the server computation time when compared with previous systems. In addition to this system provides auditing for dynamic data and supports dynamic data operation.