Cloud storage and cloud computing technologies have developed rapidly for a long time, and many users outsource the storage burden of their data to the cloud to obtain more convenient cloud storage services. Allowing users to audit the private data’s integrity has become an additional basic function of the cloud server when providing services. In 2021, based on the BLS signature and automatic blocker protocol, Jalil et al. proposed a secure and efficient cloud data auditing protocol. The protocol can realize public audit, batch audit, data update, and protect data privacy. Moreover, the automatic blocker protocol is used to realize the identity authentication of the auditor. The protocol is relatively novel, innovative, and has a larger use space. However, we found that their scheme had security problems. If the cloud server has thoughts of malicious attack, he can forge the proof that he holds users’ data with stored labels and pass the audit. Referring to the original protocol and being inspired by them, we propose an improved audit protocol. The improved protocol solves the security problem and is more effective.

Now, it is common for patients and medical institutions to outsource their data to cloud storage. This can greatly reduce the burden of medical information management and storage and improve the efficiency of the entire medical industry. In some cases, the group-based cloud storage system is also very common to be used. For example, in an medical enterprise, the employees outsource the working documents to the cloud storage and share them to the colleagues. However, when the working documents are outsourced to the cloud servers, how to ensure their security is a challenge problem for they are not controlled physically by the data owners. In particular, the integrity of the outsourced data should be guaranteed. And the secure cloud auditing protocol is designed to solve this issue. Recently, a lightweight secure auditing scheme for shared data in cloud storage is proposed. Unfortunately, we find this proposal not secure in this paper. It’s easy for the cloud server to forge the authentication label, and thus they can delete all the outsourced data when the cloud server still provide a correct data possession proof, which invalidates the security of the cloud audit protocol. On the basis of the original security auditing protocol, we provide an improved one for the shared data, roughly analysis its security, and the results show our new protocol is secure.

Cloud storage plays an important role in the data processing of edge computing. It is very necessary to protect the integrity of these data and the privacy of users. Recently, a cloud auditing scheme which can be used to smart cities has been proposed, which is lightweight and privacy-preserving. Although this scheme has very good performance and is a very valuable work, we find that there is insecurity in it. By giving two kinds of attacks, we prove that a malicious cloud server provider (CSP) can forge auditing proof and can successfully pass the verification of the third-party auditor (TPA) even if the CSP deletes the user’s data. Then, based on this scheme, we propose an improved scheme, which can resist the forgery attack from malicious CSP. Through security analysis, our scheme improves the security compared to the original scheme without reducing the efficiency.

With the advent of data outsourcing, how to efficiently verify the integrity of data stored at an untrusted cloud service provider (CSP) has become a significant problem in cloud storage. In 2019, Guo et al. proposed an outsourced dynamic provable data possession scheme with batch update for secure cloud storage. Although their scheme is very novel, we find that their proposal is not secure in this paper. The malicious cloud server has ability to forge the authentication labels, and thus it can forge or delete the user’s data but still provide a correct data possession proof. Based on the original protocol, we proposed an improved one for the auditing scheme, and our new protocol is effective yet resistant to attacks.

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