CACPA: Credible Alliance-Chain-Based Public Auditing Scheme for Cloud Storage

We propose a credible alliance-chain-based public auditing scheme (CACPA) to properly address the trust problem of third-party auditor (TPA) in the traditional audit scheme for cloud storage. Based on the non-tamperability and traceability of blockchain, we design a novel incentive mechanism to enforce honest and reliable behaviors of TPA. The basic idea is to organize TPA as a group of blockchain nodes conducting mutual surveillance. Any behavior of a TPA node will be inspected by other nodes to maintain good reputation of the group, and malicious behaviors will bring severe punishments. Accordingly, we develop system model of the proposed CACPA, as well as smart contracts to deal with transactions-related issues, such as dispute resolution. Finally, performance evaluation validates that our scheme enjoys acceptable efficiency and suits for real-world applications.