A Searchable Encryption Scheme in a Multi-user Setting for Cloud Storage

To support encrypted keyword queries on encrypted data and to access data in a multi-user setting for cloud storage, a searchable encryption scheme is proposed by combining Chinese Remainder Theorem with Public Encryption with Keyword Search. The proposed scheme enables data owners to outsource their encrypted data to the storage of cloud servers for a number of users, who are given the ability to generate valid queries and to access data without leaking any information. More importantly, the proposed scheme does not rely on shared keys to realize multi-user searchable encryption and user dynamics. Each authorized user in the proposed scheme has a unique key and can perform encrypted keyword queries on encrypted data as well as access data without knowledge of the keys of other users, such that when some users are added or removed, other users are unaffected. We prove that the proposed scheme is secure under Bilinear Diffie-Hellman and Hash Diffie-Hellman assumptions. The performance analysis shows that the proposed scheme has lower communication and storage overheads for both cloud servers and users than other existing schemes. In addition, the proposed scheme possesses features similar to that of most existing schemes in a single-user setting and does not downgrade because of supporting multiple users.