Underwater Wavelength Attack on Discrete Modulated Continuous-Variable Quantum Key Distribution.

Area of Science:

• Quantum Information Science
• Optical Communication Security
• Underwater Networks

Background:

• Continuous-variable quantum key distribution (CV-QKD) is crucial for secure communication.
• Wavelength attacks exploit beam splitter wavelength dependence to compromise CV-QKD.
• Underwater channels are vital for secure communication but less explored for QKD security.

Purpose of the Study:

• To propose and analyze wavelength attack schemes for discrete-modulated (DM) CV-QKD in underwater turbulent channels.
• To investigate the effectiveness of these attacks with and without a local oscillator (LO) intensity monitor.
• To determine the conditions under which an eavesdropper can maximize key theft.

Main Methods:

• Developed two novel wavelength attack schemes tailored for underwater DM-CV-QKD.
• Utilized the wavelength-dependent transmittance properties of fused biconical taper (FBT) beam splitters.
• Determined specific blue-green wavelengths for Eve's pulse manipulation.
• Derived a successful criterion for the attack based on channel transmittance and estimated excess noise.

Main Results:

• Both proposed wavelength attack schemes effectively reduce the estimated excess noise for Alice and Bob towards zero.
• The attack's success is contingent on selecting appropriate condition parameters based on channel transmittance.
• Numerical analysis confirms that minimizing estimated excess noise allows Eve to steal a greater number of secret keys.

Conclusions:

• Wavelength attacks pose a significant threat to underwater discrete-modulated CV-QKD systems.
• The proposed schemes are effective in both scenarios with and without an LO intensity monitor.
• Secure underwater quantum communication requires countermeasures against such wavelength-dependent exploits.