Anonymous Signature Scheme Design And Analysis

With the launch of Internet applications, some specific network security applications such as electronic cash and electronic voting objectively demand to keep the information about the user's identity and location secret. Network security has become the focus of concern. Therefore, the anonymity has become the research focus in electronic commercial activities. The research into anonymous technology has also gradually deepened. And digital signature, as one of the most important applications of the public-key cryptographic system, plays an important role in electronic services, because it can be used to protect data integrity and authenticate the identity of message transmitter. Digital signature scheme combined with anonymous technology forms anonymous signature scheme.The study to anonymous signature schemes includes two aspects. One is anonymous signature scheme which can track down the identity of the actual signer. In this situation, the anonymity of the signers' identities can be controlled by a credible authority center who can reveal the signers' identities at the appropriate time. The other is unconditional anonymous signature scheme. In this kind of signature scheme, the anonymity of the signers' identities is unconditional safe, and there is no method to reveal the identities of the signers'. Proxy signature and group signature can be used to achieve the traceability to the identity of the actual signer, and ring signature can be used to generate unconditional anonymous signature scheme.The main achievements of this thesis are listed as follows:First, we deeply investigate the designing structure of Shum-Wei scheme, point out the main shortcomings of their scheme, and present a new proxy anonymous signature scheme which can trace the signer's identity based on their scheme. The new scheme not only overcomes the shortcomings of Shum-Wei scheme, but also achieves seven properties.Second, by analyzing the identity-based group signature scheme of Zhi Ming and other people, we find that their scheme uses an unproved property of bilinear pairings, and does not meet the traceability in group signature scheme. So we improve their scheme, and prove that the improved scheme overcomes their shortcoming. The method of attack to their scheme is not feasible in the improved one.Third, the identity-based ring signature scheme of Chow and others is the most effective one at present. Based on their scheme, we present an improved identity-based ring signature scheme. The improved one is much more effective than the original one.Fourth, we present a new threshold identity-based ring signature scheme. Compared with Chow and others' scheme, the new scheme is much more effective and satisfies the security needs of ring signature, trusted authority compatibility and robustness.