Stratus: Check and Share Encrypted Data among Heterogeneous Cloud Storage

Abstract

A cloud storage service is never sufficient if it only guarantees one of data confidentiality and integrity. Remote storage without encryption could expose private information to outsiders; while storage without integrity could be appended with garbled and useless cipher. This paper presents the Stratus, an integrated encrypted storage atop of heterogeneous cloud storage. Standing on user's perspective, we focus on guaranteeing convenient access and integrity verification to the clouds. Also, Stratus preserves implicitly the folder hierarchy of the original storage and allows painless data migration and sharing without backward decryption. By the technique of dummy list, Stratus is able to perform lazy deletion, reducing access overhead. In particular, we use a novel authentication method, the Binomial Merkle Forests (BMF), to offer a lightweight and public verifiable proof of integrity checking. Other salient features of Stratus include assured deletion and space query in O(log N).