Audit as You Go: A Smart Contract-Based Outsourced Data Integrity Auditing Scheme for Multiauditor Scenarios with One Person, One Vote

The data outsourcing services provided by cloud storage have greatly reduced the headache of data management for users, but the issue of remote data integrity poses further security concerns and computing burdens. The introduction of a third-party auditor (TPA) frees data owners from the auditing burden and alleviates disputes over the audit results between data owners and cloud storage providers. However, malicious cloud servers may collude with TPAs to deceive users for financial profits. Hiring multiple auditors in a single audit assignment appears to be a method to address the above problem, but the ensuing voting issues need to be further explored. In this paper, we proposed a smart contract-based outsourced data integrity auditing scheme for multiauditor scenarios. Unlike some existing schemes using reputation like factors as their voting weights, auditors in our scheme vote equally and audit as they go, without any maintenance. This mechanism not only frees auditors from trivia not related to the auditing but also avoids the drawbacks of centralization associated with over-high voting weights. The challenge used to check the integrity of the outsourced data is jointly generated by each involved auditor. Any collusion would be detected as long as there exists more than one honest auditor in the audit. We implement and deploy the scheme as Ethereum smart contracts. With the help of blockchain, the entire auditing process is public and transparent. Both the generated data and the obtained results are persisted with immutability, which ensures the traceability of all historical audits. The comprehensive theoretical and experimental analyses demonstrate that our scheme meets the claimed targets with high efficiency and low gas costs.