Paper 2022/1101

Solutions to quantum weak coin flipping

Atul Singh Arora, California Institute of Technology
Jérémie Roland, Université Libre de Bruxelles
Chrysoula Vlachou, Instituto de Telecomunicações
Stephan Weis, Wald-Gymnasium, Berlin, Germany

Weak coin flipping is an important cryptographic primitive, as it is the strongest known secure two-party computation primitive, that classically becomes secure only when certain assumptions are made (e.g. computational hardness), while quantumly there exist protocols that achieve arbitrarily close to perfect security. This breakthrough result was established by C. Mochon in 2007 [arXiv:0711.4114], however, his proof of existence was partially non-constructive, thus, setting back the proposal of explicit protocols. In this work, we report three different solutions to the quantum weak coin flipping problem. In particular, we propose different methods that result---either analytically or numerically---in the operators needed to construct weak coin flipping protocols with different levels of security, including nearly perfect security. In order to develop these methods, we study the quantum weak coin flipping problem from both an algebraic and a geometric perspective. We also analytically construct illustrative examples of weak coin flipping protocols achieving different levels of security.

Note: Parts of the original work presented in this paper have been presented in the STOC19 ( and SODA21 ( conferences.

Available format(s)
Cryptographic protocols
Publication info
secure two-party computation quantum coin flipping
Contact author(s)
atul singh arora @ gmail com
Jeremie Roland @ ulb be
chrysoula vlachou @ lx it pt
weis @ waldygmnasium de
2022-08-29: approved
2022-08-25: received
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      author = {Atul Singh Arora and Jérémie Roland and Chrysoula Vlachou and Stephan Weis},
      title = {Solutions to quantum weak coin flipping},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1101},
      year = {2022},
      note = {\url{}},
      url = {}
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