Multiparty controlled quantum secret direct communication using   Greenberger-Horne-Zeilinger state
  Base on the idea of dense coding of three-photon entangled state and qubit transmission in blocks, we present a multiparty controlled quantum secret direct communication scheme using Greenberger-Horne-Zeilinger state. In the present scheme, the sender transmits her three bits of secret message to the receiver directly and the secret message can only be recovered by the receiver under the permission of all the controllers. All three-photon entangled states are used to transmit the secret messages except those chosen for eavesdropping check and the present scheme has a high source capacity because Greenberger-Horne-Zeilinger state forms a large Hilbert space. 
Jian Wang, Quan Zhang, Chao-jing Tang