ID-Based Encryption with Equality Test Against Insider Attack

Testing if two ciphertexts contain the same plaintext is an interesting cryptographic primitive. It is usually referred to as equality test of encrypted data or equality test. One of attractive applications of equality test is for encrypted database systems, where the database server hosts the encrypted databases and users can query if the plaintext embedded in a ciphertext on a database is equal to that in the queried ciphertext without decryption. Although it is not hard to achieve with the pairing-based cryptography, the security against the insider attack (by the database server) is a challenging task. In this paper, we propose a novel equality test scheme aiming to solve the problem. Our scheme adopts the identity-based cryptography. We prove the security of our scheme in the random oracle model.