A Practical Certificateless Signature Scheme

In Asiacrypt´03, Al-Riyami and Paterson introduced the concept of certificateless public key cryptography (CLPKC). CLPKC is a paradigm to solve the inherent key escrow problem suffered by identity-based cryptography (IBC). In this paper, we propose a practical certificateless signature (CLS) scheme based on bilinear pairings. Three pairing computations can be used in the verification algo- rithm of our scheme, in contrast to at least four pairing in the verification phase of previous provably secure CLS schemes. In addition, only one pairing which is precom- putable can be saved in the sign algorithm. The security of the proposed scheme can be proved to be equivalent to the Inverse Computational Diffie-Hellman problem and q- Strong Diffie-Hellman problem in the random oracle model.