Continuous-variable quantum digital signatures that can withstand coherent attacks

TL;DR

This paper presents a continuous-variable quantum digital signature protocol that can resist coherent attacks, offering improved security and efficiency for large-scale quantum networks, demonstrated through simulations showing significant signature length reduction.

Contribution

The authors develop a CV QDS protocol capable of withstanding coherent attacks and demonstrate high efficiency and robustness against finite-size effects and noise.

Findings

Significant reduction in signature length for large messages.

Protocol robustness against finite-size effects and excess noise.

Enhanced security against coherent attacks.

Abstract

Quantum digital signatures (QDSs), which utilize correlated bit strings among sender and recipients, guarantee the authenticity, integrity, and nonrepudiation of classical messages based on quantum laws. Continuous-variable (CV) quantum protocol with heterodyne and homodyne measurement has obvious advantages of low-cost implementation and easy wavelength division multiplexing. However, security analyses in previous researches are limited to the proof against collective attacks in finite-size scenarios. Moreover, existing multibit CV QDS schemes have primarily focused on adapting single-bit protocols for simplicity of security proof, often sacrificing signature efficiency. Here, we introduce a CV QDS protocol designed to withstand general coherent attacks through the use of a cutting-edge fidelity test function, while achieving high signature efficiency by employing a refined one-time universal hashing signing technique. Our protocol is proved to be robust against finite-size effects and excess noise in quantum channels. In simulation, results demonstrate a significant reduction of eight orders of magnitude in signature length for a megabit message signing task compared with existing CV QDS protocols and this advantage expands as the message size grows. Our work offers a solution with enhanced security and efficiency, paving the way for large-scale deployment of CV QDSs in future quantum networks.