Abstract
In recent years, there is a growing demand for cloud storage services. However, in many cloud storage services, different providers have their different restrictions, resulting in the user's inconvenience. The most criticized defect is that users can’t be sure whether the file they deleted is really gone forever in the cloud storage. The privacy of files is in question. Other work has proposed a system which allows users to manage multiple cloud storage spaces in a single window, as if all of them are concatenated. Users can add or delete space as needed, and also can encrypt their data, increasing the privacy. However, the system will cause too much burden on the server maintaining the service to do so. And the encryption service provided by third parties can’t effectively achieve differential synchronization. In order to solve the problem, we come up with a new method. Under the assistance of Rsync algorithm, we present the “Fragment Rsync” algorithm. We divide the file into certain size of “fragments", encrypt them, and save the file in the cloud storage as the form of “fragments”. When files are modified in the future, the differences we make will be synchronized to the data in the cloud storage in the unit of “fragment”. By applying this method, even if the data is encrypted by a third party, this can save the time and network traffic by only synchronize the differences between the original and revised file to the best. Users will not need to transfer any part of the file to the server anymore, which loosen the burden of the server and at the same time, elevate the privacy of the file.