Abstract: The previous multi-party non-repudiation protocols normally focus on one round message exchange. The multi-round message exchanges within the same participatores are not studied well. For the latter condition,we presented a multi-party non-repudiation protocol using key chains which can reduce the TTP's storage requirements. The protocol consists of a dispute resolution policy and four sub-protocols, i. e.，the initialization sulrprotocol, the exchange sulrprotocol, the abort sub-protocol and the recovery sulrprotocol. Technical discussions show that the protocol satisfies fairness, timeliness and confidentiality.

Key words: Security protocol, Non-repudiation, Multi-party protocol, Kcy chains