The Research On Certificateless Signature Scheme Without Bilinear Pairing

Certificateless public key cryptography system has solved the problems of identityauthentication and key escrow, which has outstanding advantages. But a certificatelesssignature without authentication is vulnerable to the public key substitution attack, and acertificateless signature is also vulnerable to malicious KGC (Key Generation Center) attackbecause KGC can get the partial private key of user. How to resist these two attacks is theresearch focus of certificateless signature. In addition, the stand or fall of a signature schemeis also measured by efficiency. Due to the high computational complexity of bilinear pairings,the schemes constructed without bilinear pairings have higher efficiency. Research thecertificateless signature respectively from safety and efficiency, the main work is as follows:By studying the security model used for analysis safety of certificateless signaturescheme, it is pointed out that the security risks existed in the schemes constructed under thissecurity model. Considering the different attack model, a improved security models isproposed, which defined a new attack rival who can generate key and fake user. The newsecurity model has higher security goals, and the certificateless signature scheme constructedunder the improved model has higher security.Through analyzing the security of a certificateless signature scheme without bilinearpairing proposed by Wang Shengbao et al, it is indicated that the scheme could not resistmalicious attack of positive dishonest KGC. For this kind of attack, a detailed attack methodis given, and an improved scheme is proposed. Security of the improved scheme is analyzedin the improved model, it shows that the scheme can resist the malicious KGC attack,maintains efficiency of the original scheme and has higher security. Meanwhile, thecommunication complexity is reduced due to the elimination of the secure channel in the improved scheme.Combined with the characteristics of proxy blind signature, a certificateless proxy blindsignature scheme without bilinear pairings is proposed on the basis of the research of thecertificateless signature. Security of the new scheme is analyzed under the discrete logarithmproblem in the finite field. It shows that the new scheme can resist malicious KGC attackfundamentally, which satisfies all the security requirements of the proxy blind signature.