Real-time POV for Cloud Storage Without Caching Hash Values of Files

Abstract: Cloud storage services are becoming very popular due to their usefulness: many companies use such services to store important files. However, there are still many unsolved security issues. Users can not verify whether the files stored in the cloud storage are correct. The content of files may be changed, and the order of write and read operations may be inconsistent. Clients need a way to ensure the consistent behavior of their cloud storage. To address this problem, we propose a light and fast way to audit files, called Real-time POV. Client devices do not need to cache any hash values of files in order to verify that the service behaves correctly, but just need to fetch two values of each 1 kB from a synchronization server before each operation. The cloud storage only needs to maintain a small structure of authenticity information, called an FBHTree, to preserve the authenticity information for its files. The clients and the cloud storage exchange attestation data with each operation. This system protects not only the clients, but also protects the service provider of cloud storage from malicious accusations. It also outperforms previous methods by one to two orders of magnitude.