Analysis and improvement of multiparty controlled quantum secure direct communication protocol

The security of a multiparty controlled quantum secure direct communication protocol (WCZT protocol) is analyzed and a new attack with teleportation is advanced. Using this attack, the receiver can gain access to the sender's secret message without the permission of any controller; therefore, this protocol is not secure. An improved version of this protocol is proposed and the security analysis shows that the improved protocol can resist the said attack and thus the goal of multiparty controlled quantum secure communication is warranted.