A Fully Secure Verifiable and Outsourced Decryption Ranked Searchable Encryption Scheme Supporting Synonym Query

Public key encryption scheme with keyword searchable (PEKS) enables one to search for encrypted keywords without compromising the confidentiality of the original data. A practical PEKS scheme should have the following properties: quickly and efficiently searchable method, ciphertext integrity, a small amount of decryption operation for user, and full security. However, there are seldom schemes that have the all properties described above. In this paper, we propose a synonym searchable encryption scheme in composite order bilinear group. Using TFxIDF method in public key system, data owner ranks keywords and their synonyms to search efficiently. Furthermore, cloud storage server only returns the first K most relevant documents. Then, the cloud transformation server verifies ciphertext integrity and pre-decrypts the ciphertext, which reduces user's decryption burden. Finally, using dual system encryption, our scheme also achieves full security under static assumption in the random oracle model. Compared with classical searchable encryption schemes, the proposed scheme has better performance in aspects of searchable efficiency, ciphertext integrity and security.