Cloud-computing is an Internet-based service relating to increasing, use, and deliver modes, which typically involves providing dynamic, easy to be expanded, and usually virtualized resources. In a conventional cloud-computing environment, a user can only implement a simple function of erasing a cloud host, which refers to labeling a memory space of the cloud host as not occupied, rather than erasing the related data of the cloud host actually, such that the cloud host still occupies a lot of system resources and results in a waste of resources. Additionally, the related data of the cloud host can be easily recovered, which may lead to a divulge of information when the cloud host has stored a lots of sensitive information related to users, and the information security is at stake.