Versioned File Backup and Synchronization for Storage Clouds

Cloud storage has become widely used for data backup and archiving. The current archiving systems typically support a specific cloud service and this vendor lock-in problem can cause a challenge in data migration and even data loss when a cloud service provider ceases to exist. We propose a system called Rosy Cloud for automatic backup and synchronization of client data on different clouds. Rosy Cloud uses a thin interface of storage cloud through HTTP requests, keeps all encrypted file versions on the cloud, and allows different devices to asynchronously synchronize with the cloud. Conflicts due to concurrent writes are detected and resolved using a DAG model. Rosy Cloud also supports secure file sharing among different users. We have implemented the Rosy Cloud prototype with three popular storage clouds. Experiments show that Rosy Cloud is effective for both backup and synchronization with low monetary cost.