Publicly-Verifiable Proofs of Storage Based on the Discrete Logarithm Problem

With the rapid development of cloud computing platforms, cloud storage services are becoming widespread in recent years. Based on these services, clients are able to store data on remote cloud servers and thereby saving their local storage. This greatly reduces the burden of clients, while it also brings certain security risks to the outsourced data. Among the risks, a critical one is data corruption, for example cloud servers may delete some rarely used outsourced data for cost saving. To prevent this risk, proof of storage (PoS) schemes are invented, which can validate the integrity of cloud data without downloading the entire data. The existing PoS schemes, however, mostly either involve complex operations e.g. bilinear pairings, or don’t support public verifiability. To fill this gap, in this paper we construct a new PoS scheme that is publicly verifiable and only requires simple cryptographic computations. We prove that our scheme is secure under the discrete logarithm assumption, in the random oracle model. Furthermore, we also show how to extend the scheme to support data updates. Finally, we implement our scheme. The simulation results demonstrate that our scheme is more computationally-efficient than the publicly-verifiable PoS schemes of Shacham and Waters (Journal of Cryptology 2013).