Quantum Hacking Against Discrete-Modulated Continuous-Variable Quantum Key Distribution Using Modified Local Oscillator Intensity Attack with Random Fluctuations

The local oscillator in a practical continuous-variable quantum key distribution system fluctuates at any time during the key distribution process, which may open security loopholes for the eavesdropper to hide her eavesdropping behaviors. Based on this, we investigate a more stealthy quantum attack where the eavesdroppers simulate random fluctuations of local oscillator intensity in a practical discrete-modulated continuous-variable quantum key distribution system. Theoretical simulations show that both communicating parties will misestimate channel parameters and overestimate the secret key rate due to the modified attack model, even though they have monitored the mean local oscillator intensity and shot noise as commonly used. Specifically, the eavesdropper's manipulation of random fluctuations in LO intensity disturbs the parameter estimation in a realistic discrete-modulated continuous-variable quantum key distribution system, where the experimental parameters are always used for constraints of the semidefinite program modeling. The modified attack introduced by random fluctuations of local oscillator can only be eliminated by monitoring the local oscillator intensity in real time, which places a higher demand on the accuracy of monitoring technology. Moreover, similar quantum hacking will also occur in a practical local local oscillator system by manipulating the random fluctuations in pilot intensity, which shows the strong adaptability and the role of the proposed attack. © 2023 American Physical Society.