Threshold Digital Signature Scheme And Its Applications

Threshold digital signature scheme is such a signature scheme that it mainly applies to the situation that we need to share the signing right to the group members through threshold method. In a typical (t , n ) threshold signature, the key of the group is shared by n members, in which no less than t members can generate the signature to represent the whole group, while any members less than t cannot complete the signature. Since Desmedt proposed the idea of threshold signature in 1991, the threshold signature has been the hot spot in the cryptography area. In recent years, through the mature of the construction of threshold signatures, the research hot spot has turned to study of the features of the threshold signature. People analyze the current schemes and propose new schemes with good features. The newest research topic on threshold signature is to combine threshold signature with other signatures like fail-stop signature and forward security signature.In this thesis, we trace the newest result and trend of the threshold signature, and focus on the combination of threshold signature scheme with other signature schemes and their relevant applications. Fail-stop signature and blind signature are two kinds of important digital signatures. We comprehensively use cryptography and number theory to construct a robust threshold fail-stop signature. Then, based on partial threshold blind signature, we propose a new threshold e-cash system. The highlight of the system is that the signer can ensure that the signature contains some specific information while the information cannot be removed or modified. Because of this feature, we can use the public information to store the expiration date so that the system can prevent the database of the bank from unlimited increasing.