Design And Analysis Of Non-Repudiation Protocol Based On Offline-like TTP

Non-repudiation service is widely employed in network applications, especially inelectronic commerce and e-mail which are bound up with people’ daily lives. Providingan effective and more-comprehensive non-repudiation service has become a hotresearch topic.Non-repudiation service should be achieved by reliable protocol model andfaultless protocol. In order to provide expected services, it needs to meet securityobjectives, which depend on the involvement of truestd third party (TTP). However, it isinevitable to overload the TTP for its heavy involvement and thus the protocol cannotensure TTP’s reliability. Hence, it is necessary to reduce the involvement of TTP to thebest extent possible while achieving security objectives. In addition, except participants’mutual cheat to gain unfair benefits, the participants may attack TTP purposefully whenrunning protocols, such as request TTP’s involvement maliciously and result in its DoS.Faced with these problems, this paper mainly completes hereinafter work on the base ofexisting research results:①the paper firstly analyses some existing protocol models in detail and presentstheir merits and demerits. And on this basis a non-repudiation protocol without a TTPhas been described. The protocol realizes probabilistic fairness with1-ε and its greateststrength is with no need for TTP. Then a non-repudiation protocol, called ZDB, with anoffline TTP has been studied and perfected. This paper has introduced point-in-time andtime bucket into the protocol and makes its participants be able to choose a moreaccurate waiting time, which could increase opportunity for completing the exchange ofinformation and decreasing the level of TTP’s involvement at the same time.②the paper has proposed a new model, called non-repudiation protocol modelbased on offline-like TTP. The model introduces custom number of exchange times,which can be used to decrease the involvement of TTP further. Besides, the paper hasanalyzed the malicious requests aiming at attacking TTP. Some responses to them havebeen proposed. Then the paper has pointed out the model’s advantages by comparingwith the existing models.③the paper has proposed a specific non-repudiation protocol, which is calledsecurity E-mail non-repudiation protocol, based on offline-like TTP. The later analysisshows that the protocol is capable of making all primary security goals with semi-mandatory and non-mandatory. In the exchange of key stage, the probabilisty ofTTP’s involvement is ε. In addition, a practicable method for preventing theparticipants’ malicious request for TTP’s involvement has been given. The twoimportant factors for choosing custom number of exchange times are discussed as well.④in the field of electronic commerce，in order to protect the reputations ofparticipants while providing non-repudiation service, the paper has presented anE-commerce non-repudiation protocol based on transparent offline-like TTP. Thus thedamage of their reputation has been avoided.