  The ability to know and verifiably demonstrate the origins of messages can
often be as important as encrypting the message itself. Here we present an
experimental demonstration of an unconditionally secure digital signature (USS)
protocol implemented for the first time, to the best of our knowledge, on a
fully connected quantum network without trusted nodes. Our USS protocol is
secure against forging, repudiation and messages are transferrable. We show the
feasibility of unconditionally secure signatures using only bi-partite
entangled states distributed throughout the network and experimentally evaluate
the performance of the protocol in real world scenarios with varying message
lengths.
