Secure and practical Quantum Digital Signatures

TL;DR

This paper evaluates and enhances practical Quantum Digital Signature protocols to ensure information-theoretic security against quantum attacks, optimizing their efficiency and closing security loopholes.

Contribution

It analyzes, amends, and optimizes existing QDS protocols based on preshared keys and universal hashing, ensuring their security and improving efficiency.

Findings

Successfully closed security loopholes in three QDS protocols.

Optimized protocol parameters for reduced key consumption and signature length.

Identified the most efficient protocol among the analyzed options.

Abstract

Digital signatures represent a crucial cryptographic asset that must be protected against quantum adversaries. Quantum Digital Signatures (QDS) can offer solutions that are information-theoretically (IT) secure and thus immune to quantum attacks. In this work, we analyze three existing practical QDS protocols based on preshared secure keys (e.g., established with quantum key distribution) and universal hashing families. For each protocol, we make amendments to close potential loopholes and prove their IT security while accounting for the failure of IT-secure authenticated communication. We then numerically optimize the protocol parameters to improve efficiency in terms of preshared bit consumption and signature length, allowing us to identify the most efficient protocol.