Comments on “Privacy-Preserving Public Auditing Protocol for Regenerating-Code-Based Cloud Storage”

Public auditing protocol is crucial for the success of cloud computing, as it can ensure the outsourced data in cloud server are not tampered by attackers. Due to its importance, public auditing protocol has received considerable attention in the past years. In 2015, Liu
et al.
proposed a privacy-preserving public auditing protocol for regenerating-code-based cloud storage (IEEE Transactions on Information Forensics and Security, 10(7):1513–1528, 2015) and claimed it is secure under the considered security model. However, in this article, we will show that their protocol is not as secure as they claimed, i.e., the proxy delegated by the data owner can forge an authenticator for any data block, which obviously invalidates their protocol’s security. We hope that by identifying the design flaw, similar weaknesses can be avoided in future protocol design.