# Security analysis of practical continuous-variable quantum key distribution systems under laser seeding attack

## TL;DR

This paper analyzes the security vulnerabilities of practical continuous-variable quantum key distribution systems under laser seeding attack and proposes a real-time monitoring scheme to enhance their security.

## Contribution

It identifies a security loophole caused by laser seeding attack and introduces a monitoring method to accurately evaluate and secure CVQKD systems.

## Key findings

- Laser seeding attack can overestimate secret key rates.
- Proposed monitoring scheme effectively detects and resists the attack.
- Security loophole in practical CVQKD systems is mitigated.

## Abstract

Here, we investigate the security of the practical one-way CVQKD and CV-MDI-QKD systems under laser seeding attack. In particular, Eve can inject a suitable light into the laser diodes of the light source modules in the two kinds of practical CVQKD systems, which results in the increased intensity of the generated optical signal. The parameter estimation under the attack shows that the secret key rates of these two schemes may be overestimated, which opens a security loophole for Eve to successfully perform an intercept-resend attack on these systems. To close this loophole, we propose a real-time monitoring scheme to precisely evaluate the secret key rates of these schemes. The analysis results indicate the implementation of the proposed monitoring scheme can effectively resist this potential attack.