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Journal of Zhejiang University(Engineering Science)

Non-repudiation protocol based on conditional trusted third party

Chun Chen

Published Jan 1, 2004• 0 citations
OpenAlex

Abstract

The idea of TTP was developed on the basis semi-trusted TTP. The term of conditional trusted third means that on the condition of third party satisfying the pre-conditions, if he behaves right, then he is trusted, else his behavior can be checked by participators of the protocol. A new protocol adopting off-line and TTP was put forward. Compared with available non-repudiation protocols, this one progresses further in reducing intervention of TTP in fair exchange.

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The idea of TTP was developed on the basis semi-trusted TTP. The term of conditional trusted third means that on the condition of third party satisfying the pre-conditions, if he behaves right, then he is trusted, else his behavior can be checked by participators of the protocol. A new protocol adopting off-line and TTP was put forward. Compared with available non-repudiation protocols, this one progresses further in reducing intervention of TTP in fair exchange.
Non-repudiation service is widely employed in information exchange and online transaction. It requires that its participants are unable to deny their involvement in specific protocol. At the same time, the service should keep fairness, which means that no one could take any advantages over the other one. Researchers have introduced a trusted third party (TTP) to realize these demands. Protocols are grouped into several categories according to the degree of TTP's involvement in protocols. Optimistic non-repudiation protocol is the most important method undoubtedly owe to its lower TTP's involvement. There are two questions. One is that whether it is possible to further decrease TTP's involvement or not. A computable optimistic non-repudiation protocol seems to be a good improvement. This is also our paper's basic protocol. The other question is about whether two types of finally evidences that produced by participants (here is Alice and Bob, and we denote this type evidences as the first type evidences) and TTP (or with the help of TTP, and we demote this type evidences as the second type evidences) are identical. If both types of evidences are not exactly the same, then it shows that TTP has taken part in process of protocol. Thus, it is certain that either participants behaved dishonest, or network went wrong. Participants' prestige will be negatively affected more or less. On the contrary, if two types of evidences are identical, then such feelings will be eliminated. This kind of TTP is called transparent TTP. In this paper, we have accomplished an optimistic non-repudiation protocol with the help of transparent TTP based on a computable non-repudiation protocol.
A non-repudiation protocol enables the fair exchange of an electronic message and an irrefutable digital receipt between two mistrusting parties over the Internet. That is, at the end of any execution instance of such a protocol, either both parties obtain their expected items or neither party does . In this paper, we first argue that it is really meaningful in practice to exploit generic fair non-repudiation protocols with transparent off-line trusted third party (TTP). Namely, in those protocols, each involved party could use any secure digital signature algorithm to produce non-repudiation evidences; and the issued evidences are the same regardless of whether the TTP is involved or not. Then, we present such a fair non-repudiation protocol to overcome some limitations and shortcomings in previous schemes. Technical discussions are provided to show that our protocol is not only secure but also the most efficient solution, compared with existing non-repudiation protocols. In addition, some potential extensions are also pointed out.
With the development of e-commence and other utilities on internet,a new security service——fair non-repudiation becomes more important and crucial.But,most current protocols depend on trusted third party(TTP),so a fair non-repudiation protocol without TTP is needed.But the existing fair protocols don't have equal security for message originator and receiver,and they can not assure the security of the message originator.In this paper,a new protocol is designed for the prior security of the originator,and a fair non-repudiation protocol without TTP based on entity's computing power is proposed to get rid of the dependence on TTP,to solve the security problems that exist when message originator and receiver's computing power are not equal.
Electronic mail delivery is one of the most important and desirable services, by which the intended recipient will get the mail if and only if the mail originator receives a valid and irrefutable proof of the receipt. The idea of conditional trusted third party has been developed on the basis of semi-trusted TTP and a suite of acceptable conditions is given. A new practical protocol for certified e-mail is presented, which can guarantee acceptable fair with interception of conditional TTP. More, the evidence in the new protocol is publicly verifiable without any restrictions on the type of signature and encryption algorithms.
Based on a short signature scheme and discrete logarithm problem,a new fair exchange protocol with the off-line semi-Trusted Third Party(TTP) is proposed.The off-line semi-TTP intervenes into the protocol in case of trouble,which makes the fair exchange optimistic.The off-line TTP need not be completely trusted,since it can get neither signature exchanged when disputation is solved.Because this protocol is based on short signature,which needs low storage and little communication,it can be used in low-bandwidth communication and low-storage environments.