With the phenomenal growth of the Internet and open networks in general, security services, such as non-repudiation, become crucial to many applications. Nonrepudiation services must ensure that when Alice sends some information to Bob over a network, neither Alice nor Bob can deny having participated in a part or the whole of this communication. Therefore a fair non-repudiation protocol has to generate non-repudiation of origin evidences intended to Bob, and non-repudiation of receipt evidences destined to Alice. In this paper, we clearly define the properties a fair non-repudiation protocol must respect, and give a survey of the most important non-repudiation protocols without and with trusted third party (TTP). For the later ones we discuss the evolution of the TTP's involvement and, between others, describe the most recent protocol using a transparent TTP. We also discuss some ad-hoc problems related to the management of non-repudiation evidences.

With the phenomenal growth of the Internet and open networks in general, security services, such as non-repudiation, become crucial to many applications. Non-repudiation services must ensure that when Alice sends some information to Bob over a network, neither Alice nor Bob can deny having participated in a part or the whole of this communication. Therefore a non-repudiation protocol has to generate non-repudiation of origin evidences intended to Bob, and non-repudiation of receipt evidences destined to Alice. In this paper, we clearly define the properties a non-repudiation protocol must respect, and give a survey of the most important non-repudiation protocols without and with trusted third party (TTP). For the later ones

this technical report, the result has been announced and a brief sketch of the proof has been given by Even when presenting a contract signing protocol [60] in 1981. This result enforces the intuition that it is impossible to "simultaneously" exchange two items, without a "referee"

Due to the explosive growth of electronic businesses carried on the Internet, nonrepudiation services turn out to be increasingly important. Non-repudiation services protect the transacting parties against any false denial that a particular event or action has taken place, in which evidence will be generated, collected and maintained to enable the settlement of disputes. Several fair non-repudiation protocols have been proposed, which support non-repudiation of origin and non-repudiation of receipt while neither the originator nor the recipient can gain an advantage by quitting prematurely or otherwise misbehaving during a transaction. However, a critical issue on how to maintain the validity of non-repudiation evidence efficiently during and after a transaction was not considered. This paper uses the idea of evidence chaining to address such a problem. Keywords: fair non-repudiation, validity of evidence, evidence chaining, dispute resolution 1 Introduction Due to the expl...

Abstract. With the development of high speed computer networks, video service on the Web has huge market potential in that the video service can be provided to subscribers with greater time and schedule exibility compared to the current cable TV system. Under the pay-perview (PPV) scheme, subscribers only need to pay for the programs that they have watched. A critical issue on PPV service is the capability of settling disputes over PPV service charges. This is especially important in the case that the Internet communication could be interrupted (by accident or deliberately) in the middle of a viewing session. This paper proposes a fair PPV billing protocol for web-based video service. With this protocol, a video service will be divided into small units, and a subscriber needs to submit cryptographic evidence which enables fair billing based on the number of units being provided in a viewing session. In addition, by the establishment of a one-way sequential link, the validity of evidence is maintained e ciently without any involvement of trusted third parties. Our scheme is light-weighted in terms of the storage requirement and computation overheads on subscribers, thus subscribers can request PPV service securely with their own smart cards regardless of their physical location.