Certificateless Public Key Encryption in the Selective-ID Security Model (Without Random Oracles)

Abstract

The concept of Certificateless Public Key Encryption (CLPKE) eliminates the use of certificates in certified Public Key Encryption (PKE) scheme and the key-escrow problem in Identity Based Encryption (IBE) scheme. Al-Riyami and Paterson first proposed a CL-PKE scheme and proved its security in their security model (AP-model) using idealized random oracles. Several generic constructions were also proposed to construct a CL-PKE scheme by composing the standard PKE and IBE schemes. Recently, it was proved that some generic constructions are not secure against chosen ciphertext attacks in light of the security goals in the AP-model. In this paper, we show that all the known generic constructions are not secure against chosen ciphertext attacks, in the AP-model or a weaker security model than the AP-model. We also propose a CL-PKE scheme which is provably secure against chosen ciphertext attacks without random oracles. Our construction is proven secure in the selective-ID security model, reflecting the feature of CL-PKE scheme.