Revocable Certificateless Public Key Encryption

The concept of a certificateless public-key system (CL-PKS) was first introduced by Al-Riyami and Paterson. The CL-PKS not only solves the key escrow problem but also retains the merit of eliminating the required certificates in the identity-based PKS. Up to now, there was little work on studying the revocation problem in existing CL-PKS constructions. In this paper, we address the revocation problem and propose the first revocable certificateless public-key encryption (RCL-PKE). We define the new syntax and security notions of the RCL-PKE and propose a concrete RCL-PKE scheme. Compared with the previously proposed CL-PKE schemes, the proposed RCL-PKE scheme retains efficiency for encryption and decryption procedures while providing an efficient revocation alternative using a public channel. Under the computational and the bilinear Diffie-Hellman assumptions, we demonstrate that our RCL-PKE scheme is semantically secure against adaptive chosen-ciphertext attacks.