Theory Of Group Signature And Its Application

Nowadays many people not only go surfing but also do business over Internet, whichengenders many security problems, and the protection for personal privacy is the most im-portant one of them. We consider this kind of situation: some employee wants to contractan agreement with the other party in the name of his company. In the real world, he mayhave the company's cachet as the right to sign on the agreement. And in the meantime, hispersonal information as an employee of this company will not be revealed through the agree-ment. Now in the digitalized world, what he should do?As we all know, in cryptography, digital signature helps people to securely sign digital-ized files and encryption helps people to securely transmit messages through Internet. Whatwe need as mentioned above is something like"encrypted signature". That is, we need thiskind of signature to ensure the authentication of the company, and the actual signer's identityis encrypted. This concept is called group signature: many users composes a group, eachgroup member interacts with outside party as one group without revealing his identity, andeach member's interaction should be and only could be traced by an entity, called groupmanager.So the topic of this dissertation is group signature. In particular, security model of groupsignatures, how to construct efficient group signatures, etc., are investigated.We discuss the whole process and every details to construct secure group signature,including mathematical fundamentals, the security models, useful building blocks and theintegrated techniques. We also show our unique opinions to some essential problems forgroup signature, including CCA2-anonymous secure, member revocation mechanism andhow to construct group signature in standard model.We investigate some applications and related problems to group signature, especiallyanonymous credential system. Based on the proposed group signature scheme, a corre-sponding anonymous credential system is also proposed.As a complicated primitive in cryptography, group signature has been well studied. Theimportant thing is, the research on group signature itself has provided fruitful methodologyand technique to cryptography.