Data storage has today emerged as a new challenge with newer modes being introduced. Cloud computing is the most prevalent method by which large amount of data can be outsourced. The concept of Third Party Auditor (TPA) was introduced in order to rid the user from the tedious task of auditing their data. The TPA checks on behalf of the data owner so that he is assured of the veracity and authenticity of his data. But this Third Party Auditor scheme has its own set of loopholes as the basic assumption is that the TPA can be trusted and is honest, but where the TPA is dishonest and any two of the three involved entities (i.e. user, TPA and Cloud Service Provider) might be in an unholy alliance then the whole system collapses. The paper proposes a solution to protect the data stored in cloud from the dishonesty of TPA. The approach batch-verifies leaf nodes and their indexes together. The proposed scheme is also suitable for dynamic outsourced auditing system. It minimizes the costs of initialization for both user and TPA, and also incurs a lower rate for dynamism at user side.

Keywords : Cloud Computing, Third Party Auditor(TPA), Authencity.