Polarization Attack on Continuous-Variable Quantum Key Distribution with a Local Local Oscillator

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Communications

Background:

• Phase noise estimation is critical for determining secret key rates in local oscillator continuous-variable quantum key distribution (LLO CVQKD).
• The phase reference, essential for LLO CVQKD, is vulnerable to eavesdropping when transmitted over insecure quantum channels.
• Practical LLO CVQKD systems often measure only a fraction of phase reference pulses due to limited measurement rates, leaving others unmonitored.

Purpose of the Study:

• To introduce and analyze a novel polarization attack scheme targeting the phase reference in LLO CVQKD systems.
• To demonstrate how an eavesdropper can leverage unmeasured phase reference pulses to conceal quantum attacks.
• To investigate the impact of this attack on the security and achievable secret key rates of LLO CVQKD.

Main Methods:

• Development of a polarization attack model against the phase reference in LLO CVQKD.
• Simulations to evaluate the effectiveness of the attack under varying transmission distances and system parameters.
• Analysis of the relationship between polarization measurement rate and system vulnerability.

Main Results:

• The proposed polarization attack allows an eavesdropper (Eve) to manipulate phase noise by controlling unmeasured phase reference pulses.
• Simulations indicate that Eve can obtain partial or complete information about the secret key rates shared between Alice and Bob as distance increases.
• The attack's success is directly linked to the proportion of unmeasured phase reference pulses.

Conclusions:

• Attacks on the phase reference pose a significant threat to the security of LLO CVQKD systems.
• Increasing the polarization measurement rate to 100% is a vital countermeasure against such polarization attacks.
• Real-time monitoring of phase reference intensity is recommended to enhance LLO CVQKD security.