| With the rapid development of computer networks, web services have been deep into every corner of people's life. However, the network brings the convenience as well as the security threats. Therefore the data transmission through the network needs cryptographic technologies to ensure the security. Digital signature technology, as an important branch of the cryptography, provides a solid foundation for carrying out network activities securely and reliably, which makes it a hot spot of information security studies.This paper focuses on the digital signature technology for the group scenario, including the dynamic group signature, proxy blind signature and their applications. The following is the layout of this paper.Firstly, a cryptanalysis of Wu Keli's dynamic group signature scheme based on bilinear pairing is given. A calculation defeat in Wu's scheme is pointed out. Additionally, a new framing attack and a new coalition attack are present.Secondly, a new forward secure group scheme based on Chinese Remainder Theorem is proposed in this paper, which only needs simple exponentiations to add or remove members; What's more, by applying dynamic accumulator to the group signature, an idea of constructing dynamic group signature on dynamic accumulator is proposed, which enables the group members to update evidence by simple multiplications. This scheme is very suitable for the group whose members are frequently changes.Meanwhile, an analysis of two proxy blind signature schemes are given,which shows the existence of forged attacks in both schemes and the dissatisfaction on un-linkability. The proxy signer can link the public signature with the information retained by him.Finally, in order to meet the practical needs of e-government, a new anonymous proxy electronic voting system is designed by combining dynamic group signature with proxy signature. It has the advantage that the election can be conducted smoothly even when the original election voters can not complete the election. |
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