Of Ghz Entangled State As Quantum Channel Quantum Secure Direct Communication

We present a quantum secure direct communication protocol by using Green-berger -Horne-Zeilinger (GHZ) entangled state via local unitary operations. In this paper, we point out that the 'quantum dialogue' communication scheme recently introduced by Nguyen can be eavesdropped on under an intercept-and-resend attack. We also give a revised control mode to detect this attack. This protocol can also generalized to a control system too. This protocol can protect the communication against a destroying-travel-qubit-type attack. Hence, within the present version two users can exchange their secret messages securely and simultaneously, and the efficiency information transmission can be successfully increased.