  Nowadays, a large amount of user privacy-sensitive data is outsourced to the
cloud server in ciphertext, which is provided by the data owners and can be
accessed by authorized data users. When accessing data, the user should be
assigned with the access permission according to his identities or attributes.
In addition, the search capabilities in encrypted outsourced data is expected
to be enhanced, i.e., the search results can better pre-sent user's intentions.
To address the above issues, ESAS, an Efficient Semantic and Authorized Search
scheme over encrypt-ed outsourced data, is proposed. In ESAS, by integrating
PRSCG (the privacy-preserving ranked search based on con-ceptual graph) and
CP-ABE (ciphertext policy attribute-based encryption), semantic search with
file-level fine-grained access authorization can be realized. In addition,
search authorization can be done in an offline manner, which can improve search
efficiency and reduce the response time. The security analysis indicate that
the proposed ESAS meets security requirement.
