Research About TTP Of Non-repudiation Protocols

With the rapid development of open networks, secure services are becoming more and more crucial to many applications. People have proposed a lot of secure requests,non-repudiation is one of them.Because that principal part of a protocol has different benefit starting point,they probably deny previous transactions according to their own need. It may bring about the other part's economic loss and shirk its own responsibilities. Non-repudiation protocols are the protocols, which guard against dishonest party dening their participating in certain business and refuse to undertake relevant duties.In electronic digital exchanges, it is easy to solve the sender's repudiation with the help of digital signature and key-protection technology, but it is difficult to solve the receiver's repudiation. Therefore, the original non-repudiation protocols only consider how to force the receiver to return the sender non-repudiation of receipt evidences, but it is ignored to consider whether certain party would take on advantage or not if he is destined to cheat. That is to say, the protocol's fairness. In recent years, non-repudiation protocols all satisfy fairness in some degree.Nowadays there are two methods about the research of non-repudiation problems. One is that both sides carry out secret exchange at the same time (or nearing same time). The other needs a trusted third party. The first is complicated to be realized, because that it requests both sides have same computing capacity. So it is not a reality. Therefore most of the non-repudiation protocols are based on a trusted third party. This paper introduces essential definitions of non-repudiation protocols first, and analyzes the trusted third party, and points out its function in inline, online and off-line protocols. The main contributions are follows:1. Proposing a fair multi-party non-repudiation protocol without trusted third party using group encryption scheme. Without bit-by-bit exchange, the protocol can resist attacks from outsiders and denial from insiders, so it is secure and efficient. The sender has a public system named as pub, and it is composed of bulletin board,...