Three-party quantum secure direct communication based on   Greenberger-Horne-Zeilinger states
  We present a three-party simultaneous quantum secure direct communication (QSDC) scheme by using Greenberger-Horne-Zeilinger (GHZ) states. This scheme can be directly generalized to $N$-party QSDC by using $n$-particle GHZ states. We show that the many-party simultaneous QSDC scheme is secure not only against the intercept-and-resend attack but also against the disturbance attack. 
Xing-Ri Jin, Xin Ji, Ying-Qiao Zhang, Shou Zhang, Suc-Kyoung Hong,   Kyu-Hwang Yeon, Chung-In Um