Cloud-assisted applications have been developed in recent years, especially in servicing the smart city. Cloud computing is an emerging technology, which combines many redundant and distributed servers to provide various applications and services. On the one hand, the users can outsource their data to the cloud and enjoy the services that are provided by the cloud anytime and anywhere. On the other hand, outsourcing the data to the cloud will reduce the local storage burden and alleviate the hardware maintenance. However, the cloud server is semi-trusted, which possibly threaten the data's security. In addition, because the data owner will not physically possess the data after outsourcing the data to the cloud, it is required to check the storage correctness and data integrity. Cloud auditing protocols are proposed to solve this problem, but the efficiency and security of previous protocols are not well. In this paper, we proposed an enhanced auditing protocol, which can reduce the verification cost greatly and offer enough security assurance. Besides, our protocol is able to resist the forgery attack in the proof verification. The security and performance analysis shows that the proposed protocol can efficiently support storage verification and privacy preserving.