Impersonating Quantum Secrets over Classical Channels

2026-01-03

IACR Cryptology ePrint Archive

AI Summary

This study addresses two fundamental questions: how to securely leverage a quantum pre-shared key for authentication over a classical channel, and whether the security of quantum money can be verified using only classical queries. By introducing the existence assumption of one-time puzzles, this work establishes—for the first time—a theoretical connection between such puzzles and the security of reusable quantum authentication schemes. It further generalizes the impossibility result that quantum money cannot achieve information-theoretic security via classical queries alone to arbitrary oracle models. The main contributions include proving that, in the absence of one-time puzzles, an eavesdropper can efficiently impersonate a legitimate party, and rigorously demonstrating that any quantum money scheme relying solely on classical queries is inherently incapable of achieving information-theoretic security.

Technology Category

• Machine Learning: Quantum Machine Learning
• Game Theory and Economic Paradigms: Mechanism Design
• Multiagent Systems: Mechanism Design

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: LLM based quality controls for crowd work
• Web Mining and Content Analysis: Web data provenance, reliability, and authenticity

Abstract

We show that a simple eavesdropper listening in on classical communication between potentially entangled quantum parties will eventually be able to impersonate any of the parties. Furthermore, the attack is efficient if one-way puzzles do not exist. As a direct consequence, one-way puzzles are implied by reusable authentication schemes over classical channels with quantum pre-shared secrets that are potentially evolving. As an additional application, we show that any quantum money scheme that can be verified through only classical queries to any oracle cannot be information-theoretically secure. This significantly generalizes the prior work by Ananth, Hu, and Yuen (ASIACRYPT'23) where they showed the same but only for the specific case of random oracles. Therefore, verifying black-box constructions of quantum money inherently requires coherently evaluating the underlying cryptographic tools, which may be difficult for near-term quantum devices.

Problem

• quantum authentication
• classical channels
• quantum money
• impersonation attack
• information-theoretic security

Innovation

• quantum authentication
• classical channel
• quantum money
• one-way puzzles
• information-theoretic security