  We present a quantum scheme for signing contracts between two clients (Alice
and Bob) using entangled states and the services of a third trusted party
(Trent). The trusted party is only contacted for the initialization of the
protocol, and possibly at the end, to verify clients' honesty and deliver
signed certificates. The protocol is {\em fair}, i.e., the probability that a
client, say Bob, can obtain a signed copy of the contract, while Alice cannot,
can be made arbitrarily small, and scales as $N^{-1/2}$, where $4N$ is the
total number of rounds (communications between the two clients) of the
protocol. Thus, the protocol is {\em optimistic}, as the cheating is not
successful, and the clients rarely have to contact Trent to confirm their
honesty by delivering the actual signed certificates of the contract. Unlike
the previous protocol [Paunkovi\'c, et al., 2017], in the present proposal, a
single client can obtain the signed contract alone, without the need for the
other client's presence. When first contacting Trent, the clients do not have
to agree upon a definitive contract. Moreover, even upon terminating the
protocol, the clients do not reveal the actual contract to Trent. Finally, the
protocol is based on the laws of physics, rather than on mathematical
conjectures and the exchange of a large number of signed authenticated messages
during the actual contract signing process. Therefore, it is {\em abuse-free},
as Alice and Bob cannot prove they are involved in the contract signing
process.
