Public cloud object storage auditing: Design, implementation, and analysis

Cloud storage auditing is a technique that enables a user to remotely check the integrity of the outsourced data in the cloud storage. Although researchers have proposed various protocols for cloud storage auditing, the proposed schemes are theoretical in nature, which are not fit for existing mainstream cloud storage service practices. To bridge this gap, this paper proposes a cloud storage auditing system that works for current mainstream cloud object storage services. We design the proposed system over existing proof of data possession (PDP) schemes and make them practical as well as usable in the real world. Specifically, we propose an architecture that separates the compute and storage functionalities of a storage auditing scheme. Because cloud object storage only provides read and write interfaces, we leverage a cloud virtual machine to implement the user-defined computations that are needed in a PDP scheme. We store the authentication tags of the outsourced data as an independent object to allow existing popular cloud storage applications, e.g., file online previewing. We also present a cost model to analyze the economic cost of a cloud storage auditing scheme. The cost model allows a user to balance security, efficiency, and economic cost by tuning various system parameters. We implemented, open-sourced the proposed system over a mainstream cloud object storage service. Experimental analysis shows that the proposed system is pretty efficient and promising for a production environment usage. Specifically, for a 40 GB sized data, the proposed system only incurs 1.66% additional storage cost, 3796 bytes communication cost, 2.9 seconds maximum auditing time cost, and 0.9 CNY per auditing monetary cost.