Publicly Verifiable Proofs of Data Replication and Retrievability for Cloud Storage

Proofs of Retrievability (PORs) permit a cloud provider to prove to the client (owner) that her files are correctly stored. Extensions of PORs, called Proofs of Retrievability and Reliability (PORRs), enable to check in a single instance that replicas of those files are correctly stored as well.In this paper, we propose a publicly verifiable PORR using Verifiable Delay Functions, which are special functions being slow to compute and easy to verify. We thus ensure that the cloud provider stores both original files and their replicas at rest, rather than computing the latter on the fly when requested to prove fair storage. Moreover, the storage verification can be done by anyone, not necessarily by the client. To our knowledge, this is the first PORR that offers public verification. Future work will include implementation and evaluation of our solution in a realistic cloud setting.