Mutually authenticated quantum direct communication based on entanglement swapping

First, a mutually authenticated quantum direct communication (QDC) protocol based on entanglement swapping is proposed in this paper. The protocol includes two phases, the first one for mutual identity authentication and the next for direct communication. Users Alice and Bob can identify each other by checking the correlation of Einstein-Podolsky-Rosen (EPR) pairs. According to basic properties of entanglement swapping, Bob just does exclusive-or operations on Alice´s public bits and his measurement results to extract Alice´s secret message in the direct communication phase. The authentication phase is proved to be secure, and there is no qubits transmission in the direct communication phase, so the protocol is completely secure. Furthermore, the presented QDC protocol is converted to a bidirectional one without information leakage unlike most bidirectional QDC protocols.