A Kind of Analysis Method of Off-Line TTP Fair Non-Repudiation Protocol

Off-line TTP fair non-repudiation protocols have been studied widely. Compared with on-line TTP fair non-repudiation protocol, off-line TTP fair non-repudiation protocols are analyzed rarely. Off-line TTP fair non-repudiation protocols are often composed by several subprotocols, which are defined as protocol cluster. In this paper, a kind of analysis method of off-line TTP fair non-repudiation protocol is proposed. There are three main points in this paper. Firstly, according to the cluster properties of off-line TTP fair non-repudiation protocol, protocols are instanced. Through instancing, non-repudiation and effectiveness of off-line TTP fair non-repudiation protocol can be analyzed within each single instance. Secondly, as asynchronous communication, sending and receiving actions can not exactly reflect true events of protocol. Through refining the actions of participants, protocols can be represented as the participants action sequence. And the participants action sequence can be used to analyze the violation of execution. Thirdly, the time determiner is introduced to express and verify the timeliness property of the protocol. Finally, two off-line TTP fair non-repudiation protocols are analyzed, among which ZG off-line TTP protocol is composed by two subprotocols and CCD off-line TTP protocol is composed by three subprotocols. The results of analysis indicate that ZG off-line TTP protocol is verified, which does not meet timeliness, and CCD off-line TTP protocol is verified which does not meet fairness.