Accountable outsourcing data storage atop blockchain

Abstract

Outsourcing data integrity auditing enables users to efficiently check whether their cloud data are stored intactly without retrieving them. However, a problem arises that how to hold the storage server accountable when the auditing results show that the data has been lost or tampered with. In this paper, we propose a blockchain-based accountable data outsourcing storage protocol, which enables users to obtain fine-grained compensation based on the damage of data. We provide an accurate and verifiable damage assessment method to achieve quantitative compensation. Specifically, the damage is assessed by the server and verified by smart contract. Furthermore, our protocol ensures the fairness of participants by deposit mechanism and smart contract. If any participant behaves dishonestly, it cannot obtain any benefit or even be punished. To reduce user’s overhead, we propose a new provable data possession scheme, PDP in short, supporting outsourcing the calculation of tags. Moreover, we provide a detailed security proof for the proposed protocol as well. Finally, we evaluate the time cost of off-chain functions and the gas cost of on-chain operations for our protocol, which demonstrates that it is practical and suitable in reality.