In the last decade data-centers have become a crucial element in our society. As a result, in the coming years there will be increased threat from hackers, who could cause outage of the data-center, extract millions of account details, or steal financial and sensitive information. One way to reduce these threats is to divide the data-center into sub data-centers, and connect them by secure links which prevent access by unauthorized users. A possible technology to connect between the sub data-centers is optical wireless communication (OWC) or free space optics (FSO). An OWC link includes an optical receiver and laser transmitter. The transmitter transmits a light beam that carries information which propagates to the receiver. The light beam carrying the information propagates through the air. In order to increase the security and make the penetration and intrusion difficult quantum key distribution (QKD) is added to the link. By doing so the information exchange between the sub data-centers is encrypted. In this paper we review up to date literature in the field, propose an implementation scheme of an OWC network in sub data-centers, and discuss ways to hack the system.
In the last decade data-centers have become a crucial element in our society. As a result, in the coming years there will be increased threat from hackers, who could cause outage of the data-center, extract millions of account details, or steal financial and sensitive information. One way to reduce these threats is to divide the data-center into sub data-centers, and connect them by secure links which prevent access by unauthorized users. A possible technology to connect between the sub data-centers is optical wireless communication (OWC) or free space optics (FSO). An OWC link includes an optical receiver and laser transmitter. The transmitter transmits a light beam that carries information which propagates to the receiver. The light beam carrying the information propagates through the air. In order to increase the security and make the penetration and intrusion difficult quantum key distribution (QKD) is added to the link. By doing so the information exchange between the sub data-centers is encrypted. In this paper we review up to date literature in the field, propose an implementation scheme of an OWC network in sub data-centers, and discuss ways to hack the system.
As the existing radio-frequency (RF) networks cannot meet the ever-increasing data rate demand, the optical wireless communication (OWC), which uses a wide untapped unregulated spectrum, has been proposed as a promising technology to overcome the RF spectrum limitations. On the other hand, with the increasing demand for high data rate and the prevalence of the broadcast-nature networks, researchers have recently come up with new mechanisms to improve secure communication using physical layer techniques. Compared to RF networks, the OWC networks are more secure and less susceptible to the interception because of the small coverage provided by LEDs, and because they work properly only in the presence of the line-of-sight (LoS) components. However, the security in OWC networks is still an issue, especially in visible light communication (VLC) when the transmitted information can be accessed by multiple users as in public areas, meeting rooms, laboratories, and libraries. That means potential eavesdroppers may be existing to gather confidential messages. This paper reviews all the conducted work on physical layer security (PLS) in two types of OWC networks, which are the VLC and free space optical (FSO) networks. Furthermore, the paper proposes several open problems in these networks to optimize and enhance the security performance.
Due to the recent rapid growth of computing technologies, today's encrypted information based on classical computational complexities will soon no longer remain secure. Quantum cryptography, or quantum key distribution (QKD), relying on the physical laws of quantum mechanics, stands out as a more powerful cryptographic solution that enables the secret key to be shared securely over publicly unsecured communication channels in the presence of eavesdroppers. QKD can be possibly implemented over both optical fiber and free-space optical (FSO) links. Compared to optical fiber, FSO has the immediate advantage of flexibility and cost-effectiveness in terms of infrastructure deployment. More interestingly, recent advancements in satellite communications using FSO links promise the future of a global QKD network for highly secure applications. This paper reviews the development of QKD over FSO for both terrestrial and satellite channels, which highlights the most up-to-date QKD protocols. Owing to how the information is encoded, different QKD protocols are classified into technology-focused categories, where their properties are reviewed and compared. The feasibility of current QKD protocols is then investigated with respect to its specific application scenarios for terrestrial and satellite FSO links, equipped with results from both theoretical and experimental studies. Based on the latest free-space QKD achievements, novel perspectives for future developments and challenges to enhance the secrecy performance and reduce implementation cost are then summarized and comprehensively discussed. The potential combination of QKD and physical layer cryptography for the newly emerging wireless mobile communications networks involved with unmanned aerial vehicles (UAV) is also introduced.
The growing role of secure communication in defense networks has increased the need for systems that remain dependable even under advanced cyber-threat conditions. In this work, we study a Quantum Key Distribution (QKD)-enabled Optical Wireless Communication (OWC) link for short-range building-to-building applications. The system is evaluated using a MATLAB-based simulation framework that models a terrestrial free-space optical channel affected by attenuation, beam divergence, pointing misalignment, turbulence-related penalties, and additive noise. Accordingly, the performance of channel impairments is investigated with respect to QBER and the achievable secret key rate using the BB84 protocol. At the same time, a regression model based on ANN is developed to estimate the secret key rate from the measurable channel parameters. Finally, the derived key is used in the example of QOTP encryption to illustrate the secure end-to-end communication. It is concluded from the results that attenuation of channels has the most profound effect on the performance of QKD, particularly under high-loss situations where the key rate significantly decreases. In summary, the results provide a practical baseline for understanding QKD behavior over terrestrial FSO links and point to the need for future experimental verification.
With the demand for economical and high-speed wireless services, Optical Wireless Communication (OWC) has attracted increasing attention in both research and the market. In the past decades, numerous optical-related techniques (e.g., LEDs, displays, cameras) and systems (e.g., VLC, LiFi, LiDAR) have been invented. OWC techniques, which are considered as a competitive mechanics in next-generation networks as an alternative to RF approaches, offer 10,000 times more bandwidth than conventional radio frequency (RF)-based wireless techniques (e.g., WiFi, LoRa, Bluetooth, LTE), as well as tremendous spatial reuse potential with even less interference. Because optical communications have a limited wavelength and travel in the line of sight (LoS) manner, the OWC is commonly thought as a secure wireless approach to confine light transmissions within physical bounds. However, in the real world, it is completely untrue. The privacy leakages and security risks broadly exist in the optical-related wireless applications including OWC networks. These threats and weaknesses have recently been the subject of several initial studies. However, they lack systematic analysis and are isolated. This survey first presents a general workflow of OWC systems, which consists of three stages: before signal emission (BSE), during signal propagation (DSP), and after signal receiving (ASV). For each stage, related risks are reviewed. Then, we summarize existing attacks in optical-related wireless applications and corresponding counter-attack solutions. Finally, we outline the future trends for improving OWC security.
Free-space optical (FSO) communication provides a promising alternative solution to the traditional radio frequency (RF) communications. Compared to the RF technology, there are many advantages of FSO communications, such as ultra-high bandwidth, license-free spectrum, low inter-channel interference, and energy-efficient transmission. The potential applications for FSO communication include the last-one-mile access link from the fiber-based backbone network, low earth orbit (LEO) satellite communications, high-altitude base station platforms or vehicles, deep-space communications, and in-building automation connections. As the FSO technology becomes mature and increasingly involved, the security and reliability requirements of such applications also become crucial. Regarding the security issues, although the FSO communication is inherently more secure than the RF counterpart due to high directivity of its line-of-sight (LOS) link, it can still suffer from optical wire-tapping attack. There are many different application schemes that an eavesdropper can still probe the FSO link. Traditionally, to protect the communication, many works have been done on encryption layer and upper network layer, such as computationally intensive cryptographic algorithms and message exchanging protocols. In recent years, physical-layer security (PLS) has been getting more attentions as it provides an extra layer of security against eavesdropping. The PLS schemes, in general can be categorized into two main categories: classical PLS and quantum key distribution (QKD) protocols. The classical PLS is based on the information theoretic security analysis, while the QKD security is guaranteed by the quantum mechanics laws. Both techniques have been studied for FSO channels. In the first half of this dissertation, we study the PLS in a LOS FSO channel using orbital angular momentum (OAM) multiplexing and show that higher secrecy capacity can be achieved using OAM multiplexing technology in the presence of atmospheric turbulence effects. Then, we proposed an adaptation scheme for QKD system over FSO channel with different QKD protocols, i.e. BB84 and decoy state protocols. By adapting the source brightness based on the channel condition, we optimized the secret key rate (SKR) of the QKD system. Furthermore, we proposed a multiple spatial modes-based QKD system with backpropagation method to increase the total SKR through parallel channels. Regarding the reliability of an optical communication system as well as information reconciliation for both PLS and QKD schemes, the forward error correction (FEC) becomes an essential technique to enable high-speed transmission. The FEC with low-density parity-check (LDPC) codes has been studied for decades from LDPC block codes to the most recent spatially-coupled (SC) LDPC codes. For FSO communications, due to the time-varying nature of FSO channels, the capability of rate adaptation is important to achieve a consistent reliable transmission. In the second half of this dissertation, we proposed unified FPGA-based architecture to implement both quasi-cyclic (QC) LDPC codes and SC-LDPC codes with rate adaptation capability. The performance is verified through FPGA emulation to show good error floor properties. To further validate the rate adaptation capability, we have built a spatial light modulator (SLM)-based FSO channel emulator to test the adaptive coding scheme. Furthermore, we have conducted a fiber-based experiment with our rate adaptative coding scheme to show that the proposed adaptive coding scheme can be also used in dynamic fiber-based networks.
Proposed paper presents a novel hybrid subject in optical wireless communications (OWC) in contribution to IoT devices of smart grids within smart sustainable cities (SSC). OWC and IoT are among the noticeably developing fields being used in smart cities, e-commerce, and even e-health. Accordingly, their constructions are entirely investigated. Also, the Metaverse virtual world, its infrastructures, and applications are expressed to clarify the OWC, IoT applications, and perspectives inherited with this virtual world. Moreover, the important factor in IoT devices, SSCs, and the Metaverse is ultra-secure communication. To cover this subject, quantum technology, quantum cryptography, as well as, quantum key distribution (QKD), and quantum IoT (IoT) for much more secure communication between IoT devices are represented. As another methodology, quantum neural networks (QNN), and their application in secure communication of IoT, and OWC systems are explained. Finally, quantum-based systems were compared with other regular methods and concluded quantum technology-based systems can have the potential to be implemented with optical wireless communications (OWC), IoT devices, and artificial intelligence (AI) to increase the security, and efficiency of communications in IoT constructions of smart sustainable cities (SSCs) elements.