Research On Certificateless Signature Schemes

Information technology is changing the world in a revolutionary way, meanwhile the importance of information security is emerging. As one of the pivotal technologies of information security, digital signatures provide authentication, integrality and incontestableness, playing an important part in military affairs, telecommunication and e-commerce. In Aisacrypt 2003, AL-Riyami and Patenson introduced the Certificateless Public Key Cryptography, which does not require the use of any certificates to ensure the authenticity of public keys, and also does not posses the key escrow property that seems to be inherent inidentity-based cryptography. Though certificateless crypotography relies on the existence of a trusted third party, called the KGC, who has the master-key, 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 Certificateless Public Key Signature is better than that of identity-based crypotography, and its sufficiency is much higher than that of the conventional PKI. In all the available certificateless signature schemes, there are so many bilinear pairing computations that the efficiency is low. Moreover, there are few certificateless signature schemes with additional properties by now.The work of this dissertation is mainly on certificateless signature. Firstly, we construct a provably secure identity-based signature. Then based on this signature, we propose the model of the certificateless, and also present a new certificateless signature without pairing. The new scheme is proved to be computationally unforgery under discrete logarithm assumption, meamwhile, it posseses a high efficiency because of avoiding of precise bilinear computations.