  Quantum digital signatures (QDS) exploit quantum laws to guarantee
non-repudiation, unforgeability and transferability of messages with
information-theoretic security. Current QDS protocols face two major
restrictions, including the requirement of the symmetrization step with
additional secure classical channels and quadratic scaling of the signature
rate with the probability of detection events. Here, we present an efficient
QDS protocol to overcome these issues by utilizing the classical
post-processing operation called post-matching method. Our protocol does not
need the symmetrization step, and the signature rate scales linearly with the
probability of detection events. Simulation results show that the signature
rate is three orders of magnitude higher than the original protocol in a
100-km-long fiber. This protocol is compatible with existing quantum
communication infrastructure, therefore we anticipate that it will play a
significant role in providing digital signatures with unconditional security.
