Multiparty Contract Signing Over a Reliable Network
Simona Orzan and Erik de Vink

Most contract signing protocols make use of a trusted third party (TTP) to
ensure fairness. It has been shown that in the crash network model, this is
inevitable. However, for stronger networks, where misbehavior is allowed but
failure excluded, the necessity of a TTP has not yet been debated. We consider
a strong network model, that includes reliable broadcast, bounded delays and
timestamps and use it to describe a simple multiparty contract signing
protocol that does not rely on a TTP. This shows that by strengthening the
assumptions on the network, the transfer of trust from one dedicated server to
the network is feasible. The result is commented in a more general setting of
multiparty protocols and problems. The correctness of the proposed protocol
for any number of participants is proven using process algebra techniques.