Noname manuscript No. (will be inserted by the editor) On the Security of Fair Non-repudiation Protocols

The date of receipt and acceptance will be inserted by the editor Abstract We analyzed two non-repudiation protocols and found some new attacks on the fairness and termination property of these protocols. Our attacks are enabled by several inherent design weaknesses, which also apply to other non-repudiation protocols. To prevent these attacks, we propose generic countermeasures that considerably strengthen the design and implementation of non-repudiation protocols. The application of these countermeasures is finally shown by our construction of a new fair non-repudiation protocol. Key words Security protocols, fair non-repudiation, protocol design, protocol analysis