Abstract
Recently, Huang et al. (2021) presented a quantum key agreement schemeto securely negotiate on a secret key employing the properties of a quantumsearch algorithm. First, the authors proposed the two-party quantum key agreement, and then they extended their work to the three-party case. Huang et al.'s protocol employs the unitary operation and single-particle measurements to negotiate on a secret key without using complex quantum technologies such as quantum memory or entangled quantum particles. The authors claimed that their protocol is secure and efficient. However, this work shows that Huang et al.'s protocol has a significant pitfall, where the private key of one user could be easily leaked to the attackers. Hence, the properties of security and fairness are not achieved. Accordingly, thetwo-party and three-party of Huang et al.'s protocol have been reviewed, and an improvementto address the shortcoming is suggested.