DPoSt: Dynamic Proof of Storage-time

Proof of storage-time (PoSt) enforces highly reliable data storage services to data owners by providing lightweight and continuous data availability or possession checks to the uploaded data. Despite being promising, current PoSt schemes mainly focus on static data that will not change after a PoSt process starts. This limitation, however, would largely undermine the practicality of PoSt schemes as they cannot be effectively used for important and emerging cloud storage services like document sharing, code collaboration, and website management that will modify the uploaded data whenever needed. In this paper, we propose DPoSt, a new PoSt system that provides continuous auditing protection to data owners while supporting efficient data updates. DPoSt is built with a tailored suite of cryptographic primitives to update the intermediate auditing proofs while reducing the changes we need to conduct for subsequent challenge and proof pairs in the PoSt process. We develop a prototype of DPoSt, and the evaluation results demonstrate the efficiency of DPoSt for supporting dynamic PoSt operations.