A secure protocol for misbehavior-penalization-based fair digital signature exchange
Chia‐Chun Wu, Wei‐Bin Lee, Woei-Jiunn Tsaur · 2007
In 2005, Zhang et al. proposed a novel fair digital signature exchange protocol that can impose a penalty on the misbehaving party. However, we have discovered a weakness concerning the fairness aspect of the protocol which will occur when an initiator tries to exchange the signature of the same document to others again. That is, the latter exchange partner can obtain the initiator's valid signature with the help of the previous exchange partner without completing the protocol, and therefore the protocol is not fair enough. In this paper, the reason for the occurrence of the unfair exchange is discussed, and an improvement to remove the weakness is proposed.