Id-based Group Digital Signature Research

Digital signature is used widely in the network now. Group digital signature is a special kind of digital signature,it includes threshold signature,group signature and ring signature.This thesis focuses on the group signature and the ring signature of the group digital signature.A participator can sign messages anonymously to stand for all the group numbers in the group signature and ring signature.The difference between them is that the anonymity can be revoked in the group signature,but the anonymity cann't be revoked in the ring signature.The two different signatures can be used in different situations.Group signature is widely used in the company or enterprise,where high anonymity is not needed.But ring signature is widely used in the high anonymous occasions.Group signature and ring signature are the main research interests at the graduate level.Two group digital signatures are constructed successfully, the main contributions are as follows:First, an identity-based aggregate signature scheme from the Weil pairing is constructed.The aggregate signature is similar to the group signature,it was considered as a kind of group signature in some literatures.The new scheme is based on the existing schemes,the new equation of signature and the new equation of verification are constructed,so some performances are improved.Compare to the former schemes, the new scheme reduces the amount of calculations and makes the form simpler. The identity of the signer is used as the public key of the system in the scheme,so the problem of public key management is solved.Second,an identity-based proxy ring signature scheme from multilinear pairing is constructed,and the feasibility and security of the new scheme are analyzed thoroughly. First,a new ID-based proxy signature scheme from bilinear pairing is constructed,it is different from the schemes which people have been suggestted.Second, a new ID-based proxy signature scheme from multilinear pairing is constructed,the second scheme actually is the extension of the first scheme.the mathematical tool extends from bilinear pairing to multilinear pairing,the structure of system extends from one key generation center to multiple key generation centers.An identity-based proxy ring signature scheme from multilinear pairing is constructed firstly. It imports several key generate centres.It can avoid the incredible key generation centres forging the signature.At the end of the thesis,we summarize the thesis,and point out the weaknesses of the new schemes,then we present the main research direction in the future.