Noname manuscript No. (will be inserted by the editor) Fair Multi-Party Non-Repudiation Protocols?

The date of receipt and acceptance will be inserted by the editor Abstract In this paper we introduce the concept of multi-party non-repudiation protocols. We define the aims of multi-party non-repudiation protocols, compare them to multi-party fair exchange and show some fun-damental differences. We present two protocols, the first one using an online trusted third party and the second one using an offline trusted third party. We also show how to modify each of these protocols in order to provide confidentiality. The definitions and the resulting protocols are more general than the only comparable work, a multi-party certified e-mail protocol. Key words Non-repudiation, fair exchange, group communications.