Design And Analysis Of Group Signature Schemes

Abstract: With the fast development of internet, digital signatures have played an important role in the aspects of information security, identity authentication, data integrity, non-repudiation, anonymity and so on. Group signatures are a sort of special digital signatures, which can allow any group members to sign messages on behalf of the group while remaining anonymity. In case of dispute later on, the manager can "open" signatures to revoke anonymity. The salient features of group signatures make them more applicable in the activitys of electronic politics and electronic commerce such as electronic voting, electronic bidding, un-traceable electronic cash and so forth. More generally, group signatures can be used to conceal group's or organization's internal structures. However, the security, efficiency or flexibility of most group signature schemes proposed at present, are not very ideal. Some more efficient group signature schemes can't prevent adversarys from colluding attacking or universally forging, as a result they can't protect the whole advantage of groups or organizations. Furthermore, most of group signature schemes can't delete group members freely so that they can't meet the needs of dynamic groups in reality. So it is very important to design secure, efficient and flexible group signature schemes. The dissertation has better try and exploration. Based on the famous RSA assumption and decisional Diffie-Hellman assumption, we propose several new group signature schemes, dynamic group signature schemes and group blind signature schemes respectively by ElGamal encryption, Rabin encryption and signature of knowledge.The following are the main researching results:1. The security of several famous group signature schemes are analyzed. We find that CM98 group signature scheme and ACJT2000 group signature scheme are not coalition-resistant. Furthermore, SHI2002 group signature scheme can't prevent adversarys from universally forging.2. We propose three new coalition-resistant group signature schemes. All or them can allow the group managers to add new members to the groups without modilying the public keys. The length of signatures are, as well as the computational effort for signing, verifying and opening, independent of the number of groupmembers. Moreover, the length of signatures of the third scheme, as well as the computational effort for signing, verifying and opening, are very small. So it is much more efficient.3.A formal concept of dynamic group signature is given. Then we discuss the requirements of security and the principles of estimating efficiency.4.We make the three coalition-resistant group signature schemes proposed in chapter three into three dynamic group signature schemes which can increase and delete group members flexibly.5.We give the concept of fair group blind signature. Based on the first CS97 group signature scheme, we construct a corresponding fair group blind signature scheme with obvious transfer protocol.6.Based on the third dynamic group signature scheme, we propose a much more efficient dynamic group blind signature scheme by the idea of Okamoto-Schnorr blind signature...