Research On Certificate-Based Undeniable Signature

The concept of certificate-based public key cryptography was introduced by Gentry in Eurocrypt 2003, which can overcome the certificate management problem in traditional public key system, as well as the private key escrow problem in identity-based public key system and the lower trust level of the trusted third party problem in the certificateless public key cryptography.The concept of undeniable signature was proposed by Chaum and Van Antwetpen in 1989. The verification of undeniable signature requires the participation of the signer to complete. Once the signer involved in the verification, it can not make the verifier to accept an invalid signature, and it also can not make the verifier to believe a valid signature is invalid.In this thesis, firstly, we construct an efficient provable certificate-based signature scheme. This scheme doesn't need any computation of the bilinear pairing in signing algorithm, and just only need one computation of the bilinear pairing in verification algorithm. So it is more efficient than the available certificate-based signature scheme. Secondly, we present a general definition and security requirements of certificate-based designated verifier signature, construct a signature scheme and give a brief analysis of its security. Finally, we present a formal definition and a security model of certificate-based undeniable signature. Then we construct a certificate-based undeniable signature scheme based on the certificate -based digital signature scheme and the certificate-based designated verifier signature scheme constructed before. We can prove the proposed scheme is secure in the random oracle model.