Survey on Public Auditing and Data Dynamics in Cloud Data Storage

Now a days, cloud computing is emerged as a powerful tool for IT enterprise. Cloud computing is a next generation of 'utility computing', which provide services at a reasonable costs i. e. pay as you go. basically cloud computing comes into picture when we think about, what an IT enterprise in general needs i. e. a way to increase capacity or add capabilities, without investing capital in new infrastructure, or purchasing new softwares. cloud computing provide services ranging from Software as a Service (SaaS), Platform as a Service (PaaS), Infrastructure as a Service (IaaS), Storage as a Service (SaaS) and many other services. In this paper we focus mainly on Storage as a service. In Storage as a service, a user puts his data on a cloud storage i. e. moving applications and data to the centralized data centers. but there may exists some security threats to that data and applications, as a cloud security is a major challenge in cloud computing. This paper studies the problem of data storage integrity in cloud computing. To simplify the task of verification of data integrity, we will take help of some Third Party Auditor (TPA), who will perform timely audit of data stored on a cloud, on behalf of client. The involvement of TPA eliminates the task of auditing that a client need to perform, to check whether his /her data is proper i. e. same as stored previously. In addition this paper focuses on data dynamics, which allow user to perform modifications to the data stored on a cloud, which may include block insertion, deletion etc. To achieve data dynamics we have applied the technique of merkle hash tree, instead of skip list (skip lists are used in previous works). In addition to auditing and data dynamics, the paper studies the efficient handling of multiple auditing tasks, by using the concept of bilinear aggregate signature, to enhance the auditing scheme where TPA can perform several auditing tasks simultaneously.