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Pulsed laser attack at 1061 nm potentially compromises quantum key distribution

Anastasiya Ponosova, Irina Zhluktova, Daria Ruzhitskaya, Daniil Trefilov, Anqi Huang, Alexey Wolf, Vladimir Kamynin, Vladimir Tsvetkov, Vadim Makarov

Abstract

Quantum key distribution systems offer cryptographic security, provided that all their components are thoroughly characterised. However, certain components might be vulnerable to a laser-damage attack, particularly when attacked at previously untested laser parameters. Here, we show that exposing 1550-nm fiber-optic isolators to 1061-nm sub-nanosecond pulsed illumination with 1.16 W average power permanently degrades their isolation at 1550 nm, while their forward transparency is less affected. One experimental sample was exposed to 17-mW average power picosecond attacking pulses that temporarily reduced its isolation below the specified guaranteed minimum value. This indicates a potential security threat in these attacking laser regimes that need to be addressed by improving security analysis for various light-injection attacks.

Pulsed laser attack at 1061 nm potentially compromises quantum key distribution

Abstract

Quantum key distribution systems offer cryptographic security, provided that all their components are thoroughly characterised. However, certain components might be vulnerable to a laser-damage attack, particularly when attacked at previously untested laser parameters. Here, we show that exposing 1550-nm fiber-optic isolators to 1061-nm sub-nanosecond pulsed illumination with 1.16 W average power permanently degrades their isolation at 1550 nm, while their forward transparency is less affected. One experimental sample was exposed to 17-mW average power picosecond attacking pulses that temporarily reduced its isolation below the specified guaranteed minimum value. This indicates a potential security threat in these attacking laser regimes that need to be addressed by improving security analysis for various light-injection attacks.

Paper Structure

This paper contains 1 section, 4 figures, 1 table.

Table of Contents

  1. Author declarations

Figures (4)

  • Figure 1: Pulsed laser schemes, output spectra, and pulse shapes. (a) Single-YDFA scheme. (b) Dual-YDFA scheme. (c) Pulse-compression scheme. BC, beam combiner; LD, laser diode; ISO, isolator; PC, polarization controller; PBS, polarization beamsplitter; CFBG, chirped fiber Bragg grating; MO, master oscillator. Black ellipses depict splices of components with distributed side-coupled cladding-pumped (DSCCP) Yb-doped fibers (so-called GTWave fiber) that have one active, Yb-doped fiber and one passive fiber within a common silicone coating. Insets show the reflection spectrum of CFBG and the autocorrelation trace (ACT). Spectra and oscillograms are normalized to their peak value.
  • Figure 2: Experimental setup. (a) Measurement of insertion loss at $1550~\nano\meter$. (b) Measurement of isolation at $1550~\nano\meter$. DFB, distributed-feedback laser diode; WDM, $1061/1550~\nano\meter$ wavelength-division multiplexer; PL, pulsed laser; ASE, $1550~\nano\meter$ amplified spontaneous emission source; TC, thermocouple, fixed on the isolator housing. Light paths with minimum loss at $1061~\nano\meter$ and $1550~\nano\meter$ are shown in green (light grey) and red (dark grey).
  • Figure 3: Isolation decrease and insertion loss of the tested samples at $1550~\nano\meter$ under illumination by the pulsed laser. At power below $600~\milli\watt$, the increase in insertion loss of sample 1 exhibits variations due to imperfect repeatability of FC/APC connection. Lines connect the data points in the order they were collected.
  • Figure 4: Isolation recovery of sample 2 immediately after illumination by $770~\milli\watt$ sub-nanosecond pulses and $17~\milli\watt$ picosecond pulses. PL is switched off at $0~\second$.