Study On Several Signature Schemes Based On Certificateless Public Key Cryptosystem

In cryptology, digital signature is one important technology which provides the authentication, integrity and unforgeability, playing an important role in e-commerce. With the development of digital signature, the digital signature schemes based on the traditional public cryptology firstly appeared, but it needs the certificate provided by CA in the process of verification of signature. In order to resolve the problem, in 1984, Shamir proposed ID-based public cryptosystem, although it resolved the existence of certificate, it brought the key-escrow problem and it does not satisfy the unforgeability in the generation of signature. In order to further resolve key-escrow, certificateless public cryptosystem appeared in 2003, it thoroughly resolved the existance of certificate and the key-escrow problems. combining the good characteristic of certificateless public key cryptosystem and the existing signature schemes, we put forward several concrete and applicable signature schemes.Through the research on the certificateless signature schemes, we find that most of the existing certificateless signature schemes are based on the bilinear pairings, they are not convenient to apply in some practical environment, and there are fewer certificateless signature schemes without pairing. Based on these ideas, we firstly present a certificateless signature scheme, it satisfies the non-repudiation and verifiability of the secret key, and we prove the unforgeability of the new scheme under the random oracle.On the basis of certificateless signature schemes, through the analysis on ring signature schemes, we firstly propose a certificateless proxy ring signature scheme without pairing. By analysis, it satisfies the distinguishability, non-identifiability, proxy secret key's dependency, proxy secret key's cancelling, proxy ring signature's anonymity, and we prove the new scheme's unforgeability based on the intractability of the discrete logarithm problem under the random oracle.Through the analysis on certificateless universal designated verifier signature scheme proposed by Mingyang in CACR2007, we found it was not very effective. By analysis, on the basis of these ideas, we present a high-efficiency certificateless universal designated verifier signature scheme.