Research On Provably Secure Proxy Blind Signature

Digital signature, which is used for identity authentication, data integrity and non-repudiation, plays an important role in electronic commerce, network security communication and so on. As the higher demand for the electronic commerce quality among people, some digital signature schemes with special properties have emerged. As a special digital signature, proxy blind signature has the advantages of both proxy signature and blind signature, which can be applied in many fields, e.g. electronic cash and electronic voting.Most of proposed proxy blind schemes were only given some heuristic analysis without formal proof, and one-more forgery was seldom considered. In addition, in most of the electronic cash systems based on proxy blind signature, the amount of electronic cash was invisible, and malicious users could forge the tracking information in most of the schemes. According to the current research on proxy blind signature, this thesis mainly study proxy blind signature schemes and other variant schemes under the random oracle model, which include proxy partially blind signature. As for the faults of electronic cash schemes based on proxy blind signature, the corresponding solutions are put forward. The main research results of this thesis are showed as follows:1. In view of the security requirements of a proxy blind signature, existential forgery of the original signer, existential forgery of the proxy signer and one-more forgery are considered. The theory of provable security is used to build a detailed security model. A proxy blind signature scheme based on bilinear parings is proposed. Under the random oracle model, the scheme is unforgeable against chosen message/warrant under the Computational Diffie-Hellman assumption and Chosen-Target assumption respectively. Because the less pairing computation is used, the scheme i n the thesis is of high efficiency compared with the previous schemes.2. In view of the faults of electronic cash schemes based on proxy blind signature,a proxy partially blind signature scheme is proposed in this thesis. According to the Huang’s model of the proxy signature, a security model of the proxy partially blind signature is given. The scheme is proved to be secure in random oracle model under the assumption of CDH. The analysis shows that the proposed scheme can satisfy the other security require ments of a proxy partially blind signature.3. The thesis analyzes Tan’s electronic cash scheme and the shortcomings of Tan’s scheme are pointed out. Based on the proposed proxy partially blind signature scheme,a new electronic cash scheme is proposed. In order to realize the visibility of the face value, the face value is embedded into common information in withdraw protocol. In order to prevent the malicious forgery of tracking information and achieve double-spending detection, the user must give a proof of the correctness of embed tracking information through signature of knowledge. Analysis shows that the proposed electronic cash scheme can satisfy no double spending, unforgeability, anonymity, practicality. The problems of electronic cash based on proxy blind signature are settled.