Recently, Lang suggested a quantum private comparison (QPC) without classical computation (Int J Theor Phys, 59(2020)2984). Lang claimed that this QPC protocol is secure against both the participant attack and the outside attack. It is pointed out in this paper that the third party (TP) can totally obtain the private binary sequences of two communicants by launching a special measurement attack; and moreover, an outside attacker can make this protocol fail by launching the disturbance attack. The corresponding methods are further put forward to overcome these drawbacks.

中文翻译：

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无需经典计算的密码分析和量子私有比较的改进

最近，Lang提出了没有经典计算的量子私有比较（QPC）（Int J Theor Phys，59（2020）2984）。Lang声称，此QPC协议可抵御参与者攻击和外部攻击。本文指出，第三方（TP）通过发起特殊的测量攻击可以完全获得两个通信者的私有二进制序列。而且，外部攻击者可以通过发起干扰攻击来使该协议失败。为了克服这些缺陷，进一步提出了相应的方法。