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An Optimistic Non-repudiation Protocol Focused on Transparent Trusted Third Party

Qiang Li, Kaigui Wu, Fang Li

Published Nov 1, 2013• 1 citation

Abstract

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.

DOI: 10.1109/hpcc.and.euc.2013.101

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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.

Fairness may be a desirable property of a non-repudiation service. Protocols can achieve fairness through the involvement of a trusted third party but the extent of the trusted third party's involvement can vary between protocols. Hence, one of the goals of designing an efficient non-repudiation protocol is to reduce the workload of the trusted third party. In this paper, we present a variant of our fair non-repudiation protocol (1996), where the trusted third party is involved only in the case that one party cannot obtain the expected non-repudiation evidence from the other party. This variant is efficient in an environment where the two parties are likely to resolve communications problems between themselves.

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.

A non-repudiation cryptographic protocol based on hybrid cryptosystem is proposed and it is a more perfect protocol.It can realize the true fairness and non-repudiation of both parties even the channels are unreliable and insecure.Usually the protocol only needs three interactions of participants and the transferring data keep confidential for others except for the sender and the receiver,whose transactions are protected.The Trusted Third Party(TTP) performs evidences verification,generation and publication and its bottleneck problem is solved completely.Finally,we give its formal analysis and prove the protocol's fairness,correctness and security.