Reply to the Comment on "Improvement of Controlled Bidirectional Quantum Direct Communication Using a GHZ State" Chin. Phys. Lett. 30 (2013) 040305^*

Most recently, Liu and Chen Chin. Phys. Lett. 30 (2013) 079901 used the tool of information theory to analyze the security of our two improved versions of the MX protocol Chin. Phys. Lett. 30 (2013) 040305, and they found out that our two improved versions still have the information leakage problem. After revisiting them with the tool of information theory again, with respect to the security, we draw the same conclusion as Liu and Chen. In addition, we point out that how to use a single quantum state as the sole quantum resource to design a bidirectional quantum secure direct communication protocol without information leakage is still a big challenge that needs to be solved.