Research On Digital Signatures Based On Certificateless Public Cryptography

Certificateless Public Key Cryptography was first introduced by AL-Riyami and Paterson in Asiacrypt 2003, which does not require the use of any certificates to ensure the authenticity of public keys, and also does not need the key escrow property that seems to be inherent in identity-based cryptography. Though certificateless cryptography relies on the existence of a trusted third party,called the KGC, who has the master-key,but the KGC only supplies a user with a partial private key, so the user's private key is not available to the KGC. A certificateless signature scheme can not be forged. Thus the security of CL-PKC is better than that of identity-based cryptography ,and its efficiency is much higher than that of the conventional PKI.Universal designated verifier signatures (UDVS) was first introduced by Steinfeld in 2003, whose schemes are digital signature schemes with additional functions which allows any holder to change freely from a signature to any designated-verifier so that the designated-verifier can verify that the message was signed in person. In this paper, considering the advantages of Certificateless Public Key Cryptography and Universal Designated Verifier Signature. On the basic of Studing, analyzing and comparing the signature system based on conventional PKI, ID-based, Certificateless, and universal designated verifier signatures, This paper proposes the signature model of the Certificateless universal designated verifier signatures, and then builds an efficient construction for certificateless universal designated verifier signature schemes based on the computational Diffie-Hellman problem. The security of the proposed scheme can be proved to be equivalent to the computational Diffie-Hellman problem with a tight reduction.