Published Paper Details:

Confidentiality, integrity and auditability have been studied for long in cryptography, and to provide security is the foundation for all modern cryptographic research. In next generation of cloud computing client store data on centralized cloud server may some challenges. This work is focusing on honesty of data stored in cloud data servers. Cloud storage is one of the service provided by Cloud computing in which data is maintained, managed, backed up remotely andmade 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. The cloud server is used only to save the encrypted blocks of data.The data integrity verification is done by using a TPA which is allow to check integrity of data periodically on rather than client. When data integrity is lost then client gets information from TPA. Not only checking of data purity also supports data dynamics. In this auditing task observes data insertions, deletions and modifications. This system is skillful of supporting both public auditability and data dynamics. Markel Hash Tree is used to improve block level authentication. In order to handle auditing tasks simultaneously, bilinear aggregate signature is used. This permits TPA to execute auditing simultaneously for many clients. In this dissertation the evaluation of multi user based TPA system is presented.