Research And Design On Some Digital Signatures With Additional Properties

Digital signature, which can prove authentication, integrity and non-repudiation, is one of the key techniques of information security and plays a very important role in E-commerce and E-government. As the deepening of digital signature research and the rapid development of E-commerce and E- government, the standard signature, which is a simple simulacrum of handwritten signature, can not meet the need in practice, thus making research on the digital signatures with additional properties becomes a main research direction in digital signature.In the thesis, we discuss some digital signatures with additional properties, including certificateless signature, certificateless blind signature, certificateless partially blind signature, ID-based signature, ID-based mediated signature, ID-based aggregate signature. The main contributions are as follows:1. An efficient certificateless signature scheme from bilinear pairing is proposed. The security of the scheme is based on the intractability of the Computational Diffie-Hellman(CDH),discrete logarithm problem (DLP). The proposed scheme is existential unforgeable in the random oracle model. The sign algorithm requires two scalar multiplications and one hash operation. The verify algorithm requires three pairing operations and two hash operations. The approach is effective to improve efficiency greatly.2. We study blind signature in certificateless cryptography, one with neither certificate nor key-escrow. The notion and construction of the certificateless blind signature scheme are first proposed. Security proof of the scheme is given. Analyses show that our scheme can enhance security.3. The certificateless partially blind signature scheme is proposed, with detail framework and security proofs. The scheme is shown to enhance security and efficiency.4. Analyses of two certificateless signature schemes improved by Cao et al. and Wang et al. are geven. The results show that their modification scheme is insecure against key replacement attack. The attack methods were presented. We then proposed a modification of their scheme and show its security.5. An efficient identity-based mediated signature scheme is proposed from bilinear pairing. The key generation centre does not issue new private keys for revoked identities and semi-trusted mediator (SEM) in advance. The private key will not be sent back to the user and SEM. Analysis shows that the proposed scheme reduces computation cost and bandwidth, and enhances security. The scheme is existential unforgeable in the random oracle model based on the intractability of the discrete logarithm problem.6. Aggregate signatures are useful in real world for reducing the size of signatures and the operation of signature verification. Cheng et al. presented an ID-based aggregate signature scheme from m-torsion groups and proved its security in the random oracle. However, we show that the original scheme is vulnerable to the inside attacks. One concrete attack method against the original scheme is given. An adversary can forge an aggregate signature by choosing appropriate parameters and make it pass verification.