Efficient revocable certificateless public key encryption with a delegated revocation authority

Quite recently, Shen et al. proposed a revocable certificateless public key encryption (RCL-PKE) scheme in the standard model, in which the key generation center (KGC) can efficiently revoke misbehaving or compromised users. However, their scheme was shown to be insecure. Moreover, the work of revoking users is executed only by the KGC, and their scheme requires high computation cost. In this paper, we propose the first secure RCL-PKE scheme with a delegated revocation authority in the standard model. We emphasize that the delegated revocation authority shares the responsibility for user revocation to reduce the load of the KGC and provide the revocation flexibility. When compared with Shen et al.'s scheme, our scheme has better performance in terms of each user's private key size and computation cost. Under the decisional bilinear Diffie-Hellman and collision-resistant hash function assumptions, we demonstrate that the proposed RCL-PKE scheme is semantically secure in the standard model.