Quantum Bidirectional Secure Direct Communication via Entanglement Swapping

In light of a quantum secure direct communication (QSDC) scheme using entanglement swapping Chin. Phys. Lett. 22(2005)18, by introducing additional local operations for encoding, we propose a bidirectional QSDC (BQSDC) protocol, in which two legitimate users can simultaneously exchange their respective messages. The rule for the users to retrieve his/her partner’s messages is derived explicitly in the most general case. Eve’s commonly used attack method has been discussed and can be detected with the security checking process.