Multi‐User Boolean Keyword Searchable Encryption With Fine‐Grained Access Control for Cloud Storage

ABSTRACT Searchable Encryption (SE) enables users to perform searches on encrypted data while preserving data privacy. Since cloud servers are platforms that provide services for a large number of users, and data owners require access control over their data, SE schemes that support multi‐user settings and access control are therefore more suitable for cloud storage. However, in existing SE schemes that support multi‐user settings and access control, most only support single‐keyword or conjunctive keyword searches, and the search time grows linearly with the total amount of data. These limitations negatively impact both the accuracy and efficiency of search operations. This work proposes an SE scheme specifically designed for multi‐user settings. Data owners can enforce fine‐grained access control policies, while a specialized retrieval structure allows the cloud to assist users in performing Boolean keyword searches with improved efficiency. The search complexity of the proposed scheme is , where denotes the number of files relevant to the queried keyword. We demonstrate the scheme's effectiveness and practicality through performance analysis.