Wavelength attack on atmospheric continuous-variable quantum key distribution

Recently, several practical wavelength attacks on continuous-variable quantum key distribution (CVQKD) were proposed based on the wavelength-dependent property of a beam splitter in Bob's station. These attack schemes are limited to the fiber channel systems with a relatively stable transmittance. However, unlike the fiber channel, the transmittance of the atmospheric channel is complex and fluctuates dramatically in time, which may invalidate the attack equations that must be satisfied in the optical fiber channel. In this paper, we propose two wavelength attack schemes against complex atmospheric CVQKD systems and formulize the two schemes based on the parameter estimation method. To verify the feasibility and availability of this attack, we deduce the success criteria for the two attack schemes. By numerical analysis, our attack schemes are proved to be feasible in the permitted parameter regimes. The secret key rate and propagation distance of CVQKD can be further overestimated by selecting the condition parameters effectively. Moreover, we discuss the possible prevention countermeasures to resist these attack schemes. The proposed method will fill the gap of wavelength attack for the implementation of practical atmospheric CVQKD.