Proxy Signature Scheme Analysis And Design

With the development of networks and the wide application of information systerms, information technology is changing the way of human existence and development in political,economic and social life. While information technology brings the benefits, it is also full of danger. The number of information crime is increasing by illegal invasion and illegal profits, which poses a challenge to the safe operation of the network. It promotes the development of information security. Cryptography is the core of information security technology. Public-key cryptography plays an increasingly important role because of its advantages. Being a legal replacement for handwritten signatures, digital signature which is based on public-key cryptography is sure to be more extensively used in the coming years. Under the various application backgrounds, many special digital signatures were proposed and several research directions come into being. Proxy signature is a typical one. The proxy signature is a signature scheme that an orignal signer delegates his or her signing capability to a proxy signer, and then the proxy signer creates a valid signature on behalf of the original signer. The receiver of the signature verifies the signature itself and the original signer's delegation together. So far, many proxy signature schemes and cryptography protocols based on them have been proposed. The security of digital signature has been troubling cryptographers. How to design a security digital signature plays an important role not only in the research of digital signature but also in the security of our country. This dissertation mainly studys the analysis and design of digital signature . Our contribution:1 This dissertation surveys the important significance of digital signature in the information security systerms and introduces the properties and required securities. Through analysing the security of some typical digital signature schemes. The dissertation describes how to design signature scheme.2 The dissertation discribes background, present situation, progress of signature, and introduces theory and categories of digital signature. Through analysing the security of some typical proxy signature and schemes, the dissertation shows how to design a digital signature and gives many applications in the e-commerce, renewing key, e-cash and mobile agent.3 Through reseaching the theory of proxy signature, we analyze some signature schemes with proxy properties and propose some new ways to study proxy signature.(1) Hu pointed that yang's scheme could not resist frame attack and public-key substitute attack, and gave a new scheme. Through the Cryptanalysis of a improved thredshold proxy signature scheme presented by Hu. It is found that this scheme had security leaks, attacked by warrant: forging the original signer. It did not satisfy the nonrepudiation. A new improved scheme was proposed, improving the security of the system.(2) Through analysing identity-based designated-verifier proxy signature, the system had serious defect. Adversary could accord to the delegated paramteters to forge the original signer. TC could not reveal the ture original signer's identity when in dispute. A new scheme was proposed, based on discrete logarithms.(3) Based on discrete logarithms, a designated-verifier threshold proxy signature scheme with known signers is proposed. It integrates the advantages of designated-verifier signature scheme and threshold proxy signature scheme. Moreover, in this scheme, the proxy signature time and the proxy message can be controlled, and the designated-verifier can ascertain the identities of the group signers who made the proxy signature. It is not necessary to send the parameter in the signature verification phase, which saves the cost of communication.