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International Conference Laser Optics (ICLO)

Fiber-optic elements spectroscopy against Trojan-horse attack in 1500 - 2000 nm range

Boris Aleksandrovich Nasedkin, Darya Tolochko, I. M. Filipov, Vladimir Chistiakov, Azat Olfatovich Ismagilov, Fedor Dmitrievich Kiselev, Anton Nikolaevich Tcypkin, V. I. Egorov

Published Jun 20, 2022• 0 citations
Publisher

Abstract

In this work, we measured transmission spectra of fiber-optic elements, which are used as countermeasures against quantum hacking in the 1500 - 2000 nm range. We found that investigated fiber-optic elements transmit light in 1800 - 2000 nm which opens possibilities for realization of trojan-horse attack on quantum key distribution systems at this range. To solve that problem, we suggest a simple way to decrease transmission in long-wavelength range.

DOI
10.1109/iclo54117.2022.9839700

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In this work, we measured transmission spectra of fiber-optic elements, which are used as countermeasures against quantum hacking in the 1500 - 2000 nm range. We found that investigated fiber-optic elements transmit light in 1800 - 2000 nm which opens possibilities for realization of trojan-horse attack on quantum key distribution systems at this range. To solve that problem, we suggest a simple way to decrease transmission in long-wavelength range.
Vulnerabilities of components used in quantum-key-distribution systems affect its implementation security and must be taken into consideration during system development and security analysis. In this paper, we investigate transmission of fiber optical elements, which are commonly used in quantum-key-distribution systems for designing countermeasures against Trojan-horse attacks, in the 150015001500--210021002100-nm\mathrm{nm}nm range. As a result, we find loopholes in their transmission spectra that open possibilities for eavesdropping. We also consider a simple passive countermeasure based on the violation of total internal reflection in a single-mode fiber, that provides additional insertion losses of at least 60 dB for double-pass Trojan-horse probe pulses for wavelengths longer than 1830 nm.
A well-protected and characterized source in a quantum key distribution system is needed for its security.Unfortunately, the source is vulnerable to light-injection attacks, such as Trojan-horse, laser-seeding, and laser-damage attacks, in which an eavesdropper actively injects bright light to hack the source unit.The hacking laser could be a high-power one that can modify properties of components via the laserdamage attack and also further help the Trojan-horse and other light-injection attacks.Here we propose a countermeasure against the light-injection attacks, consisting of an additional sacrificial component placed at the exit of the source.This component should either withstand high-power incoming light while attenuating it to a safe level that cannot modify the rest of the source, or get destroyed into a permanent high-attenuation state that breaks up the line.We demonstrate experimentally that off-the-shelf fiberoptic isolators and circulators have these desired properties, at least under attack by a continuous-wave high-power laser.
Abstract The results of investigation of the spectral characteristics of some passive fiber-optic components, such as optical isolators, circulators, spectral filters and multiplexers, used in quantum key distribution (QKD) systems and contributing to the protection of QKD system from active optical probing attacks are presented. An assessment of the required degree of isolation is also given, which ensures reliable protection of the QKD system against Trojan-horse attacks under the most stringent conditions for legitimate users. Based on the formulated requirements and measurement results, the effectiveness of protection using the investigated passive insulating components is analyzed. Using the example of calculating the insulation for the QKD system scheme presented in the work, the achievement of the required level of isolation (150 dB) in the entire considered spectral range is shown.
The Trojan-horse attacks on quantum key distribution (QKD) systems are known to be a threat to secure key sharing between two parties (Alice and Bob). To protect a QKD system against such attacks a variety of passive optical and active optical devices embedded in Alice’s and Bob’s setup are widely used. However, a security analysis against the Trojan-horse attack is required to ensure the unconditional security of a QKD system. We present a security analysis against the Trojan-horse attacks on a practical fiber-based QKD phase-coding system in 400–1700 nm spectral range. The obtained results made it possible to calculate the higher limit of average photon number returned to Eve and the probabilities of Eve’s success of the attack on a particular QKD system.
In the quantum version of a Trojan-horse attack, photons are injected into the optical modules of a quantum key distribution system in an attempt to read information direct from the encoding devices.To stop the Trojan photons, the use of passive optical components has been suggested.However, to date, there is no quantitative bound that specifies such components in relation to the security of the system.Here, we turn the Trojan-horse attack into an information leakage problem.This allows us to quantify the system security and relate it to the specification of the optical elements.The analysis is supported by the experimental characterization, within the operation regime, of reflectivity and transmission of the optical components most relevant to security.