  Digital signature is a key technique in information security, especially for
identity authentications. Compared with classical correspondence, quantum
digital signatures (QDSs) provide a considerably higher level of security,
i.e., information-theoretic security. At present, its performance is limited by
key generation protocols (e.g., BB84 or measurement-device-independent
protocols), which are fundamentally limited in terms of channel capacity.
Fortunately, the recently proposed twin-field quantum key distribution can
overcome this limit. This paper presents a twin-field QDS protocol and details
a corresponding security analysis. In its distribution stage, a specific key
generation protocol, the sending-or-not-sending twin-field protocol, has been
adopted and full parameter optimization method has been implemented. Numerical
simulation results show that the new protocol exhibits outstanding security and
practicality compared with all other existing protocols. Therefore, the new
protocol paves the way toward real-world applications of QDSs
