Publicly Auditable Provable Data Possession Scheme for Outsourced Data in the Public Cloud Using Polynomial Interpolation

Abstract

Cloud computing paradigm provides computing and storage infrastructure for the clients to outsource their data and computation. This new computing paradigm poses several security challenges. We focus on the problem of checking the possession of data by the untrusted cloud storage server. We design publicly auditable provable data possession scheme using polynomial interpolation technique. In our scheme, the client can delegate the task of verification to the Third Party Auditor. Interestingly, the client will not use any secret to compute the public metadata and client or Third Party Auditor need not to maintain any metadata for the verification of the proof. The verifier can verify the proof using public metadata and a random key kept secret for the challenge. We have focused on reducing the size of the proof returned by the cloud server to save the network bandwidth. We have defined the security and proved the security of the scheme under the group satisfying Computational Diffie Hellman assumption against a cheating cloud server. In the proposed scheme, the verifier can make unlimited number of data possession challenges to the server.