At present, Cloud computing is becoming a hot topic in the field of research and applications. It moves the application software and databases to the centralized large data centers, where the management of the data and services may not be fully trustworthy. However,this unique paradigm brings about many new security challenges, which have not been well understood. As such, it has become crucial for an archive service to be capable of providing evidence to demonstrate the integrity of data stored in it. This work studies the problem of ensuring the integrity of data storage in Cloud Computing.