Comment on “Controlled Bidirectional Quantum Secure Direct Communication with Six-Qubit Entangled States”

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  • Xiangfu Zou
  • Zhenbang Rong
  • Zhiming Huang
  • Jianfeng Liu
  • Ying Chen


Original languageEnglish
Article number43
Journal / PublicationInternational Journal of Theoretical Physics
Issue number2
Online published22 Feb 2023
Publication statusPublished - Feb 2023


In the controlled bidirectional quantum secure direct communication, two users can successfully exchange their private messages only when a third party permits. Recently, a controlled bidirectional quantum secure direct communication protocol with six-qubit entangled states was proposed (Int. J. Theor. Phys. 60(8), 2943–2950 2021). It claimed that, in the protocol, the participant Bob can decode Alice’s private message only with Charlie’s agreement. However, in this comment, it is pointed out that Bob can decode Alice’s private message without needing Charlie’s agreement by constructing an intercept-and-resend attack. Furthermore, to resist the constructed attack, an improving strategy is suggested. The comment can help designers of such protocols avoid similar mistakes in the future. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Research Area(s)

  • Controlled bidirectional quantum direct communication, Quantum cryptography, Quantum dialogue, Quantum secure direct communication

Citation Format(s)