|With the explosive growth of data, the risk and cost of data management are significantly increasing. In order to address this problem, more and more users and enterprises transfer their data to the cloud and access the data via Internet. However, this approach often results in a large volume of redundant data in the cloud. According to an IDC report, around 75% of the data are redundant across the world. ESG indicates that over 90% of the redundant data are in backup and archiving systems. The reason behind this is that multiple users tend to store similar files in the cloud. Unfortunately, the redundant data not only consume significant IT resources and energy but also occupy expensive network bandwidth. Therefore, data reduplications is urgently required to alleviate these problems in the cloud.