Provable data possession scheme with constant proof size for outsourced data in public cloud

Cloud computing paradigm poses several security challenges. In the context of data outsourcing on to the untrusted cloud storage server, we focus on the problem of providing the proof of data possession to the client to check the possession of the outsourced data at the cloud storage server without downloading the data. Reducing the proof size in the provable data possession scheme is a challenging issue. We have proposed a provable data possession scheme with reduced proof size to save the network bandwidth. We have proved the security of the scheme under Knowledge of Exponent and Discrete Logarithm assumptions against a cheating cloud server. We have analyzed the scheme for the storage cost, computation cost and communication cost. We compare the proposed scheme with the scheme available in literature for the proof size and show that our scheme generates shorter proof. In the proposed scheme, irrespective of number of data items for which proof is sought, the size of the proof returned by the server is constant.