Beating Classical Impossibility of Position Verification

Authors Jiahui Liu, Qipeng Liu, Luowen Qian

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Author Details

Jiahui Liu
  • Department of Computer Science, University of Texas at Austin, TX, USA
Qipeng Liu
  • Simons Institute for the Theory of Computing, Berkeley, CA, USA
Luowen Qian
  • Department of Computer Science, Boston University, MA, USA


The authors would like to thank Ran Canetti and Shih-Han Hung for their helpful discussions.

Cite AsGet BibTex

Jiahui Liu, Qipeng Liu, and Luowen Qian. Beating Classical Impossibility of Position Verification. In 13th Innovations in Theoretical Computer Science Conference (ITCS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 215, pp. 100:1-100:11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


Chandran et al. (SIAM J. Comput. '14) formally introduced the cryptographic task of position verification, where they also showed that it cannot be achieved by classical protocols. In this work, we initiate the study of position verification protocols with classical verifiers. We identify that proofs of quantumness (and thus computational assumptions) are necessary for such position verification protocols. For the other direction, we adapt the proof of quantumness protocol by Brakerski et al. (FOCS '18) to instantiate such a position verification protocol. As a result, we achieve classically verifiable position verification assuming the quantum hardness of Learning with Errors. Along the way, we develop the notion of 1-of-2 non-local soundness for a natural non-local game for 1-of-2 puzzles, first introduced by Radian and Sattath (AFT '19), which can be viewed as a computational unclonability property. We show that 1-of-2 non-local soundness follows from the standard 2-of-2 soundness (and therefore the adaptive hardcore bit property), which could be of independent interest.

Subject Classification

ACM Subject Classification
  • Theory of computation → Cryptographic protocols
  • Security and privacy → Authorization
  • Security and privacy → Public key (asymmetric) techniques
  • Theory of computation → Quantum query complexity
  • Theory of computation → Quantum complexity theory
  • cryptographic protocol
  • position verification
  • quantum cryptography
  • proof of quantumness
  • non-locality


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