We analyzed the security of the multiparty quantum secret sharing (MQSS)protocol recently proposed by Zhang, Li and Man [Phys. Rev. A \textbf{71},044301 (2005)] and found that this protocol is secure for any othereavesdropper except for the agent Bob who prepares the quantum signals as hecan attack the quantum communication with a Trojan horse. That is, Bob replacesthe single-photon signal with a multi-photon one and the other agent Charliecannot find this cheating as she does not measure the photons before they runsback from the boss Alice, which reveals that this MQSS protocol is not securefor Bob. Finally, we present a possible improvement of the MQSS protocolsecurity with two single-photon measurements and six unitary operations.
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机译：我们分析了Zhang，Li和Man [Phys。 Rev. A \ textbf {71}，044301（2005）]，发现该协议对任何其他窃听者都是安全的，除了代理Bob会准备攻击特洛伊木马的量子通信时准备量子信号。也就是说，Bob用多光子替换了单光子信号，而另一个代理Charlie却找不到这种作弊，因为她没有测量光子，然后从老板Alice跑回去，这表明该MQSS协议对于Bob并不安全。最后，我们提出了通过两个单光子测量和六个单元操作对MQSS协议安全性的可能改进。
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