Traceable Anonymous Signature And Its Applications To Electronic Commerce

With the development of internet, electronic commerce is being used widely, and the importance of information security is paid much more attention. As one of the main techniques realizing information security, digital signature is applied widely to electronic commerce. In order to protect the privacy of the users, anonymous signatures are used usually. Generally, anonymous signatures include unconditionally anonymous signatures and traceable anonymous signatures. The unconditional anonymity of unconditionally anonymous signatures may be abused and may be applied to crimes, while the traceable anonymous signatures can avoid these.This thesis mainly focused on the research of traceable anonymous signatures including group signature, group blind signature, partially blind signature and convertible user designating confirmer partially blind signature. Also, this thesis includes the applications of these traceable signatures to some important areas of electronic commerce, such as electronic auction, electronic cash, and electronic exchange. The main contributions are summarized as follows.1. An efficient protocol that proves a committed number lying in a specific interval is proposed. The existing protocols that proves a committed number lying in a specific interval mostly prove that integer is no less than and then repeat the same method to prove that is no less than . While using the proposed protocol only once, a verifier can convince that the committed number is in the interval [a, b].2. A simple membership revocation method in ACJT group signature scheme is given. First, the knowledge proof of divisibility is given. Then, a group member uses it to prove that the public key in his certificate divides exactly the public key product issued by the group manager. In the proposed revocation method, the group manager only needs one division and one exponentiation when a group member is deleted, while the signing and verifying procedure are independent of the number of current group members and excluded members, as well as the original group public key and membership certificates needn't be changed.3. An improved VLR group signature scheme is given based on Nakanishi et al.'s VLR group signature scheme. The signature length in the improved scheme is shortened about 10% than that in the original scheme. Also, an electronic auction system with multiple auction houses is proposed based on the improved VLR group signature scheme.4. A new VLR group signature scheme is proposed based on q-SDH assumption and DTDH assumption. The proposed scheme not only has traceability and BU-anonymity which the previous schemes also have, but also has exculpability; Furthermore, the signature length in the proposed scheme is shortened about 10%~47% than that in the existing schemes.5. Two fair electronic cash systems with multiple banks and without trustees are constructed by use of group blind signature. In the proposed e-cash systems, a shop owning suspicious e-coin and the bank having issued the coin can collaborate to find the user using secret sharing scheme with the help of the Central Bank. Furthermore, under abnormal situation such as blackmailing, kidnapping etc., the bank issues marked e-coin to protect the user.6. An efficient partially blind signature scheme is proposed, and according to it, a fair electronic payment protocol is given. The proposed partially blind signature scheme has advantage in computation costs and signature size over the existing schemes. And the given fair electronic payment protocol does not need trustees.7. A new convertible user designating confirmer partially blind signature scheme is proposed. In the proposed scheme, the signature length is shortened 25% and the computation costs are reduced about 36% than those in Huang et al.'s scheme.