Local oscillator fluctuation opens a loophole for Eve in practical continuous-variable quantum-key-distribution systems

Abstract

We consider the security of practical continuous-variable quantum key distribution implementation with the local oscillator (LO) fluctuating in time, which opens a loophole for Eve to intercept the secret key. We show that Eve can simulate this fluctuation to hide her Gaussian collective attack by reducing the intensity of the LO. Numerical simulations demonstrate that, if Bob does not monitor the LO intensity and does not scale his measurements with the instantaneous intensity values of LO, the secret key rate will be compromised severely.

Continuous-variable quantum key distribution under the local oscillator intensity attack with noiseless linear amplifier

“…(22). However, it is unsecured in evidence [17]. Alice and Bob cannot discover the partial information intercepted by Eve under the LOIA.…”

“…One is to attack the signal beam with a traditional Gaussian collective attack. The other is to attack the LO beam with an intensity attenuation [17] which is a non-changing phase attenuator A shown in Fig. 1 …”

“…In this paper, the protocol with or without monitoring specially represents that Bob's measurement is performed by scaling with the monitoring instantaneous value or the initial LO intensity, respectively. The covariance matrix of Alice's and Bob's mode with and without monitoring can be derived [17], separately, as follows, virtually equivalent protocol in the EB scheme based on coherent states and homodyne measurement. A state |λ sent through a Gaussian channel under the LOIA with parameters T and ε, finally applying a successful amplification with parameter g, has the same covariance matrix γ AB as a state |λ g sent through a Gaussian channel under the LOIA with transmittance T g and excess noise ε g without the NLA (Color figure online)…”

Performance Improvement of Plug-and-Play Dual-Phase-Modulated Quantum Key Distribution by Using a Noiseless Amplifier

“…A recent demonstration of one-way GMCS CVQKD has been achieved over 150 km of optical fiber by controlling excess noise [12]. However, the ignorance of the nonlocal arrangement of LO will lead to wavelength attacks [14], calibration attacks [15] and LO fluctuation attacks [16], which are all related to the loopholes of LO. Therefore, self-referenced CVQKD without sending an LO is proposed, and it can effectively remove the loopholes introduced by the LO transmission [17].…”

Quantum hacking on quantum key distribution using homodyne detection

“…While the theoretical security of CV-QKD protocols has been established [12,[15][16][17], the study of practical security of CV-QKD devices is far from sufficient (see for example, [18][19][20][21][22][23]). This is mostly due to the relative youth of the technology.…”