A Secure Key Aggregate Searchable Encryption with Multi Delegation in Cloud Data Sharing Service

As the amount of data generated in various distributed environments is rapidly increasing, cloud servers and computing technologies are attracting considerable attention. However, the cloud server has privacy issues, including personal information and requires the help of a Trusted Third Party (TTP) for data sharing. However, because the amount of data generated and value increases, the data owner who produces data must become the subject of data sharing. In this study, we use key aggregate searchable encryption (KASE) technology, which enables keyword search, to efficiently share data without using TTP. The traditional KASE scheme approach only discusses delegation of authority from the data owner to another user. However, if the delegated entity cannot perform time-critical tasks because the shared data are unavailable, the delegate must further delegate the rights given to other users. Consequently, this paper proposes a new KASE scheme that enables multi-delegation without TTP and includes an authentication technique between the user and the server. After that, we perform informal and formal analysis using BAN logic and AVISPA for security evaluation, and compare the security and performance aspects with existing schemes.