Secure File Storage System Among Distributed Public Clouds

This paper studies the technology of file storage and retrieval in multiple public clouds based on secret sharing. The research is based on a local storage and multiple public cloud storage to achieve the exchange of data between local storage and public cloud storage. Users can view files, upload files, download files, delete files, and retrieve files through local clients. A file storage directory tree is provided which records the file nodes. Through this storage directory tree, users can examine the structure of file storage on the client, add nodes, that is the simulation of deleting files, and delete nodes, that is the simulation of downloading files. After symmetric encryption, the source file which users upload through the client is stochastically deposited into multiple cloud-storage spaces in the form of encrypted file. Based on the idea of Shamir secret sharing, as the original secret, the storage directory tree is divided into several sub-secrets each of which is deposited individually into a specified cloud-storage space. During the separation, the key data which used for the reconstruction of the original secret is preserved in the local-storage space. The symmetric key is generated by an algorithm, and the seed of the key is preserved in the simulated local storage. The purpose of the study is to improve the data security of public cloud storage, reduce the risk of user data leakage, and provide users with convenient and practical system services.