Single‐Photon Based Three‐Party Quantum Secure Direct Communication with Identity Authentication

Multipartite quantum secure direct communication (MQSDC) enables multiple message senders to simultaneously and independently transmit secret messages to a message receiver through quantum channels without sharing keys. Existing MQSDC protocols all assume that all the communication parties are legal, which is difficult to guarantee in practical applications. In this study, a single‐photon based three‐party QSDC protocol with identity authentication is proposed. In the protocol, the message receiver first authenticates the identity of two practical message senders. Only when the identity authentication is passed, the legal message senders can encode their messages by the hyper‐encoding technology. In theory, two bits of messages can be transmitted to the message receiver in a communication round. The protocol can resist the external attack and internal attack, and guarantee the security of the transmitted messages and the identity codes of each legal message sender. The secret message capacity of the protocol is simulated with two‐decoy‐state method. The maximal communication distance between any two communication parties can reach ≈$\approx$31.75 km with weak signal and decoy state pulses. The three‐party QSDC protocol can be extended to a general MQSDC protocol and has important application in the further practical MQSDC field. This paper proposes a single‐photon based three‐party quantum secure direct communication protocol with identity authentication. Only the authenticated legal message senders can send their messages to the receiver simultaneously. The protocol can guarantee the absolute security of the transmitted messages and each legal message sender's identity codes in theory. It has important applications in the further quantum network field.