Spy: A QoS-Aware Anonymous Multi-Cloud Storage System Supporting DSSE

Constructing an overlay storage system based on multiple personal cloud storages is a desirable technique and novel idea for cloud storages. Existing designs provide the basic functions with some customized features. Unfortunately, some important issues have always been ignored including privacy protection, QoS and cipher-text search. In this paper, we present Spy, our design for an anonymous storage overlay network on multiple personal cloud storage, supporting a flexible QoS awareness and cipher-text search. We reform the original Tor protocol by extending the command set and adding a tail part to the Tor cell, which makes it possible for coordination among proxy servers and still keeps the anonymity. Based on which, we proposed a flexible user-defined QoS policy and employed a Dynamic Searchable Symmetric Encryption (DSSE) scheme to support secure cipher-text search. Extensive security analysis prove the security on privacy preserving and experiments show how different QoS policy work according to different security requirements.