Certificateless Dynamic Data Sharing Scheme With File Recommendation and Integrity Auditing Functions in Cloud–Fog Environment

In the fog assisted cloud storage environment, data owners can share data efficiently and conveniently. It solves the network congestion problem in the traditional cloud centric sharing mode. In recent research work, Tian et al. proposed an identity-based cloud–fog data sharing scheme [Computers & Security, 105(2021), ID: 102245]. This scheme proposes the concept of "valid auditing" for the storage of cloud–fog data for the first time, and improves the efficiency of auditing in the data sharing process based on user behavior prediction. However, carefully study their scheme, it was found that the data sharing scheme has an audit vulnerability: the cloud server does not need to store the original data after observing system parameters, but can still return a proof that can pass the verification of the auditor. Therefore, in this article, the security analysis of Tian et al.'s work is first presented. Meanwhile, to avoid key escrow attack in identity-based data sharing mechanisms, this article proposes a certificateless scheme. In addition, our proposed scheme also supports efficient dynamic updates and privacy protection against the third-party auditor. More importantly, this article adopts a data file recommendation algorithm that is more suitable for cloud–fog environments and has higher accuracy than the scheme of Tian et al. Finally, behavior analysis and security analysis indicate that the proposed scheme has high efficiency and good security and is suitable for convenient data sharing in cloud–fog environment.