Recently, Li et al. (Int J Theor Phys: DOI: 10.1007/s10773-020-04588-w, 2020) proposed a multiparty quantum key agreement protocol via non-maximally entangled cluster states. They claimed that the proposed protocol can help all the involved participants have equal influence on the final shared key. However, this study points out a loophole that makes Li et al.'s protocol suffer from a collusion attack, i.e. several dishonest participants can conspire to manipulate the final shared key without being detected by others. To avoid this loophole, an improvement is proposed here.

中文翻译：

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通过非最大纠缠簇状态对量子密钥协议的共谋攻击和反击

最近，李等人。(Int J Theor Phys: DOI: 10.1007/s10773-020-04588-w, 2020) 提出了一种通过非最大纠缠簇状态的多方量子密钥协商协议。他们声称，提议的协议可以帮助所有参与的参与者对最终的共享密钥具有同等的影响力。然而，这项研究指出了一个漏洞，使 Li 等人的协议遭受串通攻击，即几个不诚实的参与者可以合谋操纵最终的共享密钥而不会被其他人发现。为了避免这个漏洞，这里提出一个改进。