Study On Ring Signature Schemes

The information age brings us the infinite business opportunities and conveniences, but there is also full of the hidden troubles and dangers. Networks could be easily attacked, which result in leaking important information, lightly the enterprises or departments will be sink in to paralyze, seriously the national security and societie's stability will be endangered. Therefore, information security have already become the key that relates to the national economy and the people's lifetime. However, digital signature is one of the key tools in information security. Because of In different applied environments, there are different special signature schemes, such as group signature, blind signature, proxy signature, threshold signature, ring signature, etc. Among them, ring signature resolved the problem of completely anonymity to signer. For example, the worker of a factory want to exposure that the manager's corrupttion, but he(she) does not want to reveal his(her) own identity. He(she) can make use of the ring signature technique, which makes the manager only know one of workers (ring members) in his factory had exposured him, but he never knows who is the real revealer(ring member) if the revealer's identity is not opened to the public by himself(herself). The ring signature scheme is a simplified group signature scheme, in which a member in the ring signs with his private key and other members' public key without getting other's grant. It overcomes the defect of administrator's excessive power and is unconditional anonymity to signer. Applications of ring signature in anonymous electronic election, electronic government, electronic cash system, key distribution of key management and secure multi party computation, makering signature consequently become one of the most hottopics of current researches. Proxy ring signature is the combination of proxy signature and ring signature scheme. It has advantages of proxy signature and ring signature. It is very useful when proxy signers need to sign messages on behalf of the original signer while providing anonymity, such as in electronic cash or anonymous electronics election, etc.This thesis mainly focuses on the following aspects: the digital signature based on elliptic curve;the proxy ring signature based on bilinear pairings;the ID-Based proxy ring signature from bilinear pairings.1)A digital signature scheme based on elliptical curve with keys was constructed, which has the advantage of the general one-key digital signature based on elliptical curve. So it is more efficient than digital signature scheme based on RSA .On the other hand, it is more secure than former scheme by using two keys. At the same time the scheme was expanded to having thjee and more base-point, this scheme is more useful when greater security is required.2) A proxy ring signature scheme based on bilinear pairings is presented. The scheme and some previous proxy ring signature schemes also compute (n+1) time bilinear pairings at signature verification, when signature verification, there are 2n-l pairings computation in existing proxy ring signature scheme. But our scheme has not computational cost of bilinear pairings at signature generation. So as compared with existed proxy ring signature scheme, our scheme is more efficient. Finding out that the verification equation of A-S scheme in [56] is incorrect, this thesis gives the correct verification equation. Futhermore, the new scheme has advantage of both proxy signature and ring signature. It is very useful when proxy signers need to sign messages on behalf of the original entity while providing anonymity, such as in electronic cash or anonymous electronics election, etc.3) An efficient ID-Based proxy ring signature is given. It overcomes the common blemish in the existing schemes that computations increased linearly withthe number of signers. There neednot any pairings computation when signature is generated in the proposed new scheme, and only two pairings computation when signature is verified regardless of the number of signers , so it is more efficient. In addition, this thesis also points out the defects in[59]: First, the operation field is incorrect in the step of proxy key generation;second ,it is not a proxy ring signature because it is not unconditional anonymity to actual signer.