Abstract
In 2003, Al-Riyami and Paterson introduced a new public key encryption paradigm called Certificateless Public Key Encryption (CL-PKE), which like Identity-Based Encryption (IBE) is certificatefree, and meanwhile which unlike IBE but similar to certificate-based encryption is key-escrow-free. In this paper, based on a heuristic observation on some existing IBE schemes and PKE schemes, we propose a general approach to build a CL-PKE solution, which makes use of a simple combination of an IBE scheme, a Diffie-Hellman type key establishment algorithm and a secure hash-function. Following this approach we construct two efficient concrete CL-PKE schemes and formally analyse their security in the random oracle model.