Privacy-Preserving Public Auditing for Secure Cloud Storage

Privacy-Preserving Public Auditing for

Secure Cloud Storage

ABSTRACT :

Cloud Computing is the long dreamed vision of computing as a utility, where users can remotely store their data into the cloud so as to enjoy the on-demand high quality applications and services from a shared pool of configurable computing resources. By data outsourcing, users can be relieved from the burden of local data storage and maintenance. However, the fact that users no longer have physical possession of the possibly large size of outsourced data makes the data integrity protection in Cloud Computing a very challenging and potentially formidable task, especially for users with constrained computing resources and capabilities. Thus, enabling public auditability for cloud data storage security is of critical importance so that users can resort to an external audit party to check the integrity of outsourced data when needed. To securely introduce an effective third party auditor (TPA), the following two fundamental requirements have to be met: 1) TPA should be able to efficiently audit the cloud data storage without demanding the local copy of data, and introduce no additional on-line burden to the cloud user; 2) he third party auditing process should bring in no new vulnerabilities towards user data privacy. In this paper, we utilize and uniquely combine the public key based homomorphic authenticator with random masking to achieve the privacy-preserving public cloud data auditing system, which meets all above requirements. To support efficient handling of multiple auditing tasks, we further explore the technique of bilinear aggregate signature to extend our main result into a multi-user setting, where TPA can perform multiple auditing tasks simultaneously. Extensive security and performance analysis shows the proposed schemes are provably secure and highly efficient.

INTRODUCTION:

Data outsourcing to cloud storage servers is raising trend among many firms and users owing to its economic advantages. This essentially means that the owner (client) of the data moves its data to a third party cloud storage server which is supposed to - presumably for a fee - faithfully store the data with it and provide it back to the owner whenever required.

As data generation is far outpacing data storage it proves costly for small firms to frequently update their hardware whenever additional data is created. Also maintaining the storages can be a difficult task. Storage outsourcing of data to cloud storage helps such firms by reducing the costs of storage, maintenance and personnel. It can also assure a reliable storage of important data by keeping multiple copies of the data thereby reducing the chance of losing data by hardware failures.

Storing of user data in the cloud despite its advantages has many interesting security concerns which need to be extensively investigated for making it a reliable solution to the problem of avoiding local storage of data. In this paper we deal with the problem of implementing a protocol for obtaining a proof of data possession in the cloud sometimes referred to as Proof of retrievability (POR).This problem tries to obtain and verify a proof that the data that is stored by a user at a remote data storage in the cloud (called cloud storage archives or simply archives) is

Not modified by the archive and thereby the integrity of the data is assured.

Such verification systems prevent the cloud storage archives from misrepresenting or modifying the data stored at it without the consent of the data owner by using frequent checks on the storage archives. Such checks must allow the data owner to efficiently, frequently, quickly and securely verify that the cloud archive is not cheating the owner. Cheating, in this context, means that the storage archive might delete some of the data or may modify some of the data.

CHAPTER 02

SYSTEM ANALYSIS :

PROBLEM DEFINITION:

Storing of user data in the cloud despite its advantages has many interesting security concerns which need to be extensively investigated for making it a reliable solution to the

problem of avoiding local storage of data. Many problems like data authentication and integrity (i.e., how to efficiently and securely ensure that the cloud storage server returns correct and complete results in response to its clients’ queries, outsourcing encrypted data and associated difficult problems dealing with querying over encrypted domain were discussed in research literature.

EXISTING SYSTEM:

The traditional cryptographic technologies for data integrity and availability, based on Hash functions and signature schemes cannot work on the outsourced data. it is not a practical solution for data validation by downloading them due to the expensive communications, especially for large size files. Moreover, the ability to audit the correctness of the data in a cloud environment can be formidable and expensive for the cloud users. Therefore, it is crucial to realize public audit ability for CSS, so that data owners may resort to a third party auditor, who has expertise and capabilities that a common user does not have, for periodically auditing the outsourced data. This audit service is significantly important for digital forensics and credibility in clouds. To implement public audit ability, the notions of proof of retrievability and provable data possession have been proposed by some researchers. Their approach was based on a probabilistic proof technique for a storage provider to prove that clients’ data remain intact.

LIMITATIONS OF EXISTING SYSTEM:

Ø Lack of rigorous performance analysis for constructed audit system greatly affects the practical application of this scheme.

Ø it is crucial to develop a more efficient and secure mechanism for dynamic audit services, in which possible adversary’s advantage through dynamic data operations should be prohibited

Ø Single TPA to audit for all files and to take more time to auditing the files.

PROPOSED SYSTEM:

                       In this paper, we introduce a dynamic audit service for integrity verification of untrusted and outsourced storages. Our audit system, based on novel audit system architecture, can support dynamic data operations and timely abnormal detection with the help of several effective techniques, such as fragment structure, random sampling, and index-hash table. Furthermore, we propose an efficient approach based on probabilistic query and periodic verification for improving the performance of audit services. A proof of- concept prototype is also implemented to evaluate the feasibility and viability of our proposed approaches. Our experimental results not only validate the effectiveness of our approaches, but also show our system has a lower computation cost, as well as a shorter extra storage for integrity verification

ADVANTAGES OF PROPOSED SYSTEM:

Ø    A fragment technique is introduced in this paper to improve performance and reduce extra storage.

Ø    The audit activities are efficiently scheduled in an audit period, and a TPA needs merely access file to perform audit in each activity.

Ø    Each TPA to audit for a batch of files and to save the times for auditing the files.