Design And Analysis Of Group Signature Schemes

With the fast development of Internet, digital signatures have played animportant role in the aspects of information security, identity authentication,data integrity, non-repudiation, anonymity and so on. Group signatures are asort of special digital signatures, the salient features of group signatures makethem more applicable in the activities of electronic politics and electroniccommerce such as electronic voting, electronic bidding, and untraceableelectronic cash and so on. It is very important to analyze and improve theschemes proposed, and design secure, efficient and flexible group signatureschemes. Some famous group signature schemes and some ones newlyproposed are analyzed and improved in the dissertation. And a dynamicsub-group signature scheme with forward security are also proposed.The main contributions are as follows:1, The security of some improved schemes of CS97 and. the secondscheme of CS97 are analyzed and coalition attack is implemented on thoseschemes, then an improved scheme which is coaliton resistant is proposed.2, The security of three group signature schemes of the same class isanalyzed and coalition attack on those schemes is implemented, then animproved scheme which is coaliton resistant is proposed.3, The security of a classic group signature scheme is analyzed andcoalition attack on the scheme is implemented, then an improved schemewhich is coaliton resistant is proposed.4, The security of a newly proposed group signature scheme is analyzedand coalition attack on the scheme is implemented, the scheme's revocationprotocol is also proved not secure, group users could cheat when they sign, sothat their signature would also be valid when they are revocated.The scheme isalso proved not satisfying the unlinkability.5, A sub-group signature scheme with forward security is proposed. Theforward security, compositional integrity, unlinkability of sub-group signatureand some other safety properties are achieved at the same time. The scheme isbulding without signture of knowledge, so it is more efficient than the previous schemes.