Cloud computing is a promising computing model that enables convenient and on-demand network access to a shared pool of configurable computing resources. The first offered cloud service is moving data into the cloud. data owners let cloud service providers host their data on cloud servers and data consumers can access the data from the cloud servers. This new paradigm of data storage service also introduces new security challenges, because data owners and data servers have different identities and different business interests. Therefore, an independent auditing service is required to make sure that the data is correctly hosted in the Cloud. This paper surveys protocols that verify remote data possession. These protocols have been proposed as a primitive for ensuring the long-term integrity and availability of data stored at remote untrusted hosts. In this survey, we analyze several of these protocols, compare them with respect to expected security guarantees and discuss their limitations.