Analysis And Design On Certificateless Digital Signature Schemes

In order to solve the problem of certificate management in the traditional public key cryptosystems and the key escrow in the identity-based cryptography, Al-Riyami and Paterson introduced the concept of certificateless public key cryptosystems in2003. The certificateless public key cryptosystems has become one of the hot topics in cryptographic research area. In this thesis, we focus on the certificateless signature schemes including the follows three content:we analyze the security of some existing certificateless signature schemes, design some new certificateless signature schemes with the security proof. Our main contributions are summarized as follows.1. We analyze the security of two signature schemes based on bilinear parings, and give public-key replacement attack and universal forgery attack on Gorantla et al.’s pairing-based certificateless signature scheme and Selvi et al.’s identity-based aggregate signature scheme respectively.2. We present the public-key replacement attack on Su et al.’s certificateless sig-nature scheme, and propose an improved certificateless signature scheme. The improved scheme more efficient than the original scheme, and the improved scheme is also proved to be secure against existential forgery under adaptively chosen message attack in the random oracle model.3. We design a certificateless signature scheme without pairings. We also do com-pare on efficiency between the proposed scheme and the existing certificateless signature schemes without pairings. Finally, the proposed scheme is proved to be secure against existential forgery under adaptively chosen message attack in the random oracle model on the discrete logarithm problem.