Data storage is an important application of cloud computing. With a cloud computing platform, the burden of local data storage can be reduced. However, services and applications in a cloud may come from different providers, and creating an efficient protocol to protect privacy is critical. We propose a verification protocol for cloud database entries that protects against untrusted service providers. Based on identity-based encryption (IBE) for cloud storage, this protocol guards against breaches of privacy in cloud storage. It prevents service providers from easily constructing cloud storage and forging the signature of data owners by secret sharing. Simulation results confirm the availability and efficiency of the proposed protocol.