Controlled Secure Direct Communication by Using GHZ Entangled State
  We present a controlled secure direct communication protocol by using Greenberger-Horne-Zeilinger (GHZ) entangled state via swapping quantum entanglement and local unitary operations. Since messages transferred only by using local operations and a public channel after entangled states are successfully distributed, this protocol can protect the communication against a destroying-travel-qubit-type attack. This scheme can also be generalized to a multi-party control system. 
Yan Xia, Chang-Bao Fu, Feng-Yue Li, Shou Zhang, Kyu-Hwang Yeon,   Chung-In Um