Advanced Security in Visible Light Communication Systems

Abstract

The broadcast nature of the wireless optical channel in visible light communication (VLC) arises security vulnerabilities while working in open or public indoor spaces, where a passive eavesdropper (Eve) can extract information from the modulated light signals spreading across the room. The commonly implemented key-based ciphering methods used to securely transfer the data between the access point (AP) and user equipment (UE) are vulnerable to the continuing development in computational power including quantum computing. Considering the above-mentioned practical challenges, the objective of this thesis is to develop and investigate novel advanced security schemes, which can reduce the ability of a passive Eve to access the transmitted message via the physical layer (optical medium) of the indoor VLC system. The main approaches proposed in the conducted research include location-aware physical layer security (PLS) and quantum key distribution (QKD). For developing the PLS algorithms based on the location of the UE in the room, this thesis proposes to implement a novel single light-emitting diode (LED)-based uplink visible light positioning scheme and provides a closed-form geometrical solution for the minimum optical FOV constraints to provide ubiquitous localisation, where the simulation results indicate the 90-th percentile accuracy of 5 cm in the absence of ambient light in the room. Subsequently, this thesis proposes a novel location-centric singular value decomposition (SVD)-based beamforming scheme to provide PLS via signal processing. The comparative numerical analysis shows that the proposed SVD-based beamforming scheme enhances data confidentiality by significantly narrowing the secure communication zone area around UE’s location by over 90% in comparison to the commonly implemented zero-forcing beamforming and achieves reasonable secrecy capacity. Another unique machine learning (ML)-based PLS strategy exploiting UE’s position information is proposed in this thesis, which classifies the VLC AP nearest to the UE’s location to transmit the data via point-to-point channel allocation. The numerical simulations show reliable classification performance, and it is observed that the proposed PLS approach establishes a pre-defined trust boundary (i.e., closed access), which is indicated by the optical footprint of the LED associated with the selected AP. Furthermore, this thesis explores an integrated dual-level security system for the VLC channel utilising both the BB84 QKD protocol and PLS, where the latter exploits the beam directivity to enhance the confidentiality of the system. The BB84 QKD protocol used for the generation of the secret shared key between Alice and Bob is simulated while considering the quantum channel impairments and a weak coherent source generating multiphoton states. According to the results, for the average number of photons > 20 a higher secret key fraction of 0.4 is achieved but at the expense of paving the way for the photon number splitting attack, hence reducing the bit error rate (BER) for Eve to 2.4×10-2. However, the BER achieved for Eve is much higher than that of Bob (i.e., 3.7×10-3), due to limitations imposed by the PLS. Finally, the thesis concludes by highlighting the open issues for potential future research.

Date of Award	29 Nov 2024
Original language	English
Awarding Institution	Northumbria University
Supervisor	Hoa Le Minh (Supervisor), Fary Ghassemlooy (Supervisor) & Stanislav Zvánovec (Supervisor)