Security Analysis and Improvement of Source Independent Quantum Random Number Generators with Imperfect Devices

TL;DR

This paper investigates security loopholes in practical source-independent quantum random number generators caused by device imperfections, proposes countermeasures, and enhances their security for high-speed, real-world applications.

Contribution

It identifies measurement loopholes in SI-QRNGs, evaluates their impact, and introduces countermeasures to improve security and practicality in high-speed systems.

Findings

Measurement loopholes can compromise security in SI-QRNGs.

Countermeasures like recalculating entropy and monitoring improve security.

The protocol is effective for high-speed, secure quantum random number generation.

Abstract

A quantum random number generator (QRNG) as a genuine source of randomness is essential in many applications, such as number simulation and cryptography. Recently, a source-independent quantum random number generator (SI-QRNG), which can generate secure random numbers with untrusted sources, has been realized. However, the measurement loopholes of the trusted but imperfect devices used in SI-QRNGs have not yet been fully explored, which will cause security problems, especially in high-speed systems. Here, we point out and evaluate the security loopholes of practical imperfect measurement devices in SI-QRNGs. We also provide corresponding countermeasures to prevent these information leakages by recalculating the conditional minimum entropy and adding a monitor. Furthermore, by taking into account the finite-size effect,we show that the influence of the afterpulse can exceed that of the finite-size effect with the large number of sampled rounds. Our protocol is simple and effective, and it promotes the security of SI-QRNG in practice as well as the compatibility with high-speed measurement devices, thus paving the way for constructing ultrafast and security-certified commercial SI-QRNG systems.