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On the Physical Layer Security of Visible Light Communications Empowered by Gold Nanoparticles

Geonho Han, Hyuckjin Choi, Ryeong Myeong Kim, Ki Tae Nam, Junil Choi, Theodoros A. Tsiftsis

TL;DR

This paper tackles eavesdropping in visible light communications by exploiting the chiroptical properties of gold nanoparticle (GNP) plates to induce differential effects for left- and right-circular polarization. A CP-domain VLC channel model is developed that incorporates GNP plates and linear polarizers; the authors design MRT precoding for the intended symbol and a null-space artificial-noise projector and optimize transmitter and Bob polarizer angles to maximize secrecy rate without requiring Eve CSI. Suboptimal yet practical polarizer-angle solutions are derived and shown to incur negligible performance loss, while simulations in indoor scenarios demonstrate significantly higher secrecy rates and a larger Bob–Eve symbol error-rate gap compared to prior schemes. The approach offers a low-cost, hardware-amenable method for securing VLC links in indoor environments and could be extended to multi-user, cross-polarization, and wavelength-division schemes.

Abstract

Visible light is a proper spectrum for secure wireless communications because of its high directivity and impermeability in indoor scenarios. However, if an eavesdropper is located very close to a legitimate receiver, secure communications become highly risky. In this paper, to further increase the level of security of visible light communication (VLC) and increase its resilience against to malicious attacks, we propose to capitalize on the recently synthesized gold nanoparticles (GNPs) with chiroptical properties for circularly polarized light resulting the phase retardation that interacts with the linear polarizer angle. GNP plates made by judiciously stacking many GNPs perform as physical secret keys. Transmitters send both the intended symbol and artificial noise to exploit the channel variation effect by the GNP plates, which is highly effective when an eavesdropper is closely located to the legitimate receiver. A new VLC channel model is first developed by representing the effect of GNP plates and linear polarizers in the circular polarization domain. Based on the new channel model, the angles of linear polarizers at the transmitters and legitimate receiver are optimized considering the effect of GNP plates to increase the secrecy rate in wiretapping scenarios. Simulations verify that when the transmitters are equipped with GNP plates, even if the eavesdropper is located right next to the legitimate receiver, insightful results on the physical layer security metrics are gained as follows: 1) the secrecy rate is significantly improved and 2) the symbol error rate gap between the legitimate receiver and eavesdropper becomes much larger due to the chiroptical properties of GNP plates.

On the Physical Layer Security of Visible Light Communications Empowered by Gold Nanoparticles

TL;DR

This paper tackles eavesdropping in visible light communications by exploiting the chiroptical properties of gold nanoparticle (GNP) plates to induce differential effects for left- and right-circular polarization. A CP-domain VLC channel model is developed that incorporates GNP plates and linear polarizers; the authors design MRT precoding for the intended symbol and a null-space artificial-noise projector and optimize transmitter and Bob polarizer angles to maximize secrecy rate without requiring Eve CSI. Suboptimal yet practical polarizer-angle solutions are derived and shown to incur negligible performance loss, while simulations in indoor scenarios demonstrate significantly higher secrecy rates and a larger Bob–Eve symbol error-rate gap compared to prior schemes. The approach offers a low-cost, hardware-amenable method for securing VLC links in indoor environments and could be extended to multi-user, cross-polarization, and wavelength-division schemes.

Abstract

Visible light is a proper spectrum for secure wireless communications because of its high directivity and impermeability in indoor scenarios. However, if an eavesdropper is located very close to a legitimate receiver, secure communications become highly risky. In this paper, to further increase the level of security of visible light communication (VLC) and increase its resilience against to malicious attacks, we propose to capitalize on the recently synthesized gold nanoparticles (GNPs) with chiroptical properties for circularly polarized light resulting the phase retardation that interacts with the linear polarizer angle. GNP plates made by judiciously stacking many GNPs perform as physical secret keys. Transmitters send both the intended symbol and artificial noise to exploit the channel variation effect by the GNP plates, which is highly effective when an eavesdropper is closely located to the legitimate receiver. A new VLC channel model is first developed by representing the effect of GNP plates and linear polarizers in the circular polarization domain. Based on the new channel model, the angles of linear polarizers at the transmitters and legitimate receiver are optimized considering the effect of GNP plates to increase the secrecy rate in wiretapping scenarios. Simulations verify that when the transmitters are equipped with GNP plates, even if the eavesdropper is located right next to the legitimate receiver, insightful results on the physical layer security metrics are gained as follows: 1) the secrecy rate is significantly improved and 2) the symbol error rate gap between the legitimate receiver and eavesdropper becomes much larger due to the chiroptical properties of GNP plates.
Paper Structure (13 sections, 46 equations, 10 figures, 1 table)

This paper contains 13 sections, 46 equations, 10 figures, 1 table.

Table of Contents

  1. Introduction
  2. Technical Literature Review
  3. Motivation
  4. Our Contributions
  5. System Model
  6. GNP Properties
  7. Effective Channel Modeling
  8. Precoder Design and Linear Polarizer Angle Optimization
  9. Precoder design
  10. Linear polarizer angle optimization
  11. Analysis of proposed design
  12. Simulation Results
  13. Conclusion

Figures (10)

  • Figure 1: The conceptual figure of proposed GNP-empowered VLC system.
  • Figure 2: The VLC channel paths between a transmitter and a receiver generated by WiThRay Choi:2023.
  • Figure 3: The chiroptical properties of GNP plates depending on the different sizes with the same pattern.
  • Figure 4: The chiroptical properties of GNP plates with respect to the different patterns with the same size. The pitch means the gap between adjacent GNPs.
  • Figure 5: The channel variation effect by elaborated arrangement of GNPs.
  • ...and 5 more figures