Blockchain-based fair payment smart contract for public cloud storage auditing

Cloud storage plays an important role in today’s cloud ecosystem. Increasingly clients tend to outsource their data to the cloud. In spite of its copious advantages, integrity has always been a significant issue. The audit method is commonly used to ensure integrity in cloud scenarios. However, traditional auditing schemes expect a third-party auditor (TPA), which is not always available in the real world. Also, the former scheme implies a limited pay-as-you-go service, as it requires the client to pay for the service in advance. In this paper, we aim to address the aforementioned drawback by adopting blockchain to replace TPA and designing a blockchain-based fair payment smart contract for public cloud storage auditing. In our system, data owner and cloud service provider (CSP) will run a blockchain-based smart contract. The contract ensures that the CSP is required to submit data possession proof regularly. The CSP gets paid only if the verification is passed; otherwise, it gets no remuneration but has to pay the penalties. To reduce the number of interactions in the execution of contract, we present the notion of non-interactive public provable data possession and design a blockchain-based smart contract for public cloud storage auditing based on this primitive.