Physical Layer Security Techniques Research Articles

Cooperative communication design of physical layer security enhancement with social ties in random networks

Social relationships among wireless nodes play a key role of wireless networks to establish trusted services applications. Owing to inherent randomness of wireless environment, the security and confidentiality of wireless information transmission urgently needs to be addressed. Physical layer security (PLS) technique has been proposed as an effective solution of securing wireless communications, by exploiting channel characteristics. Different from most previous works that ignored relationship among wireless nodes, this paper studies secrecy performance of cooperative communication based random network with social friendships, and presents four types of cooperative relaying and jamming schemes. In particular, proposed schemes introduce the concept of Local Friendship Circle (LFC) and Long-range Friendship Annulus (LFA), in which the optimal relay and friendly jammers are selected based on their physical locations and channel state information (CSI). In the context of PLS, the connection outage probability (COP) and secrecy outage probability (SOP) are introduced to evaluate performance of designed strategies, and their mathematical expressions are derived with the tools of stochastic geometry. Numerical simulations validate the theoretical analysis and illustrate the influence of system configurations on reliability and security performances.

Multiple Optical Beam Switching for Physical Layer Security of Visible Light Communications

Visible light communications (VLC) techniques are viewed as promising candidates for the upcoming B5G&6G mobile wireless networks. Due to the broadcast nature of VLC channel, physical layer security (PLS) techniques have been considered and explored to improve the confidentiality of VLC transmission. Nevertheless, almost all current designs focus on application scenarios including sufficient transmitters and fail to match the scenarios with limited, even just two transmitters. For addressing this challenge, in this article, multiple optical beam switching scheme is proposed. Unlike conventional Lambertian beam based technique paradigm, the given scheme tentatively utilize two asymmetry non-Lambertian beams to configure each VLC transmitter. Numerical results show that, for the typical center legitimate receiver, compared with about 0.92 bps/Hz average secrecy capacity (SC) of the conventional Lambertian beam configuration, up to 5.55 bps/Hz average SC gain is acquired through the proposed beam switching scheme. Moreover, this potential gain will be enhanced to about 5.86 bps/Hz when three candidate non-Lambertian beams are available for each transmitter.

Challenges in Physical Layer Security for Visible Light Communication Systems

This article highlights challenges associated with securing visible light communication (VLC) systems by using physical layer security (PLS) techniques. Motivated by the achievements in PLS studies for radio frequency (RF) communication, many PLS techniques for VLC systems were also rigorously investigated by tailoring the RF techniques to the VLC environment. However, careful consideration of the inherent differences between RF and VLC systems is still needed. By disregarding these differences, an eavesdropper could be given an opportunity to wiretap the VLC systems, even when PLS techniques are employed to protect them. Crucially, the fact that it is often not possible to know the number and locations of eavesdroppers in real VLC systems may allow eavesdroppers to devise various cooperative eavesdropping methods. By examining a few examples of the possible eavesdropper threats that can occur in VLC systems, this article offers novel insights into the vulnerabilities of state-of-the-art PLS schemes for VLC systems. Although the focus of the paper is mostly on these weaknesses, some potential solutions are also briefly proposed with a view to stimulating discourse in the community.

Physical layer security techniques for data transmission for future wireless networks

The broadcast nature of wireless communication systems makes wireless transmission extremely susceptible to eavesdropping and even malicious interference. Physical layer security technology can effectively protect the private information sent by the transmitter from being listened to by illegal eavesdroppers, thus ensuring the privacy and security of communication between the transmitter and legitimate users. Thus, the main design goal of physical layer security is to increase the performance difference between the link of the legitimate receiver and that of the eavesdropper using well-designed transmission schemes. The development of mobile communication presents new challenges to physical layer security research. This paper provides a survey of the physical layer security research on various promising mobile technologies from secure key generation and keyless techniques, including secure key generation, directional modulation (DM), spatial modulation (SM), covert communication, and intelligent reflecting surface (IRS)-aided communication. Finally, the future topics and the unresolved technical challenges are presented in physical layer security for mobile communications.

Secure OFDM with Peak-to-Average Power Ratio Reduction Using the Spectral Phase of Chaotic Signals.

In this paper, a new physical layer security technique is proposed for Orthogonal Frequency Division Multiplexing (OFDM) communication systems. The security is achieved by modifying the OFDM symbols using the phase information of chaos in the frequency spectrum. In addition, this scheme reduces the Peak to Average Power Ratio (PAPR), which is one of the major drawbacks of OFDM. The Selected Mapping (SLM) technique for PAPR reduction is employed to exploit the random characteristics of chaotic sequences. The reduction with this algorithm is shown to be similar to that of other SLM schemes, but it has lower computational complexity and side information does not have to be sent to the receiver. The security of this technique stems from the noise like behavior of chaotic sequences and their dependence on the initial conditions of the chaotic generator (which are used as the key). Even a slight difference in the initial conditions will result in a different phase sequence, which prevents an eavesdropper from recovering the transmitted OFDM symbols.

Physical layer secure key generation with nonlinear preprocessing of RSS for power constraint wireless networks

SummaryThere has been growing attention in physical layer security (PLS) techniques for wireless networks. PLS techniques are based on physical layer characteristics and are less computationally complex than traditional cryptographic approaches, which work on higher layers of networks. Physical layer key generation (PLKG) is one of the prominent key based PLS techniques that exploits reciprocity and randomness of wireless fading channel to establish secure communication between two transceivers. PLKG system consists of five stages as RSS measurement, its preprocessing, quantization and encoding, key reconciliation, and privacy amplification. Each stage has a substantial role in deciding the performance of PLKG system, but RSS preprocessing offers wide scope in performance improvement for the system. In this work, we propose PLKG system using a new class of preprocessing technique first time, which is nonlinear. We formulated the problem uniquely and considered two nonlinear techniques: nonlinear preprocessing using expander (NLPE) and nonlinear preprocessing using compressor (NLPC). We analyzed the performance of system using NLPE and NLPC and found NLPE is most suitable. Performance of the system is evaluated in terms of bit disagreement rate (BDR) and randomness of keys. Results show that NLPE performs extremely well, as compared with linear approach and without preprocessing approach, especially at low signal to noise ratio (SNR) range. Emerging wireless networks such as internet of things (IoT), centralized radio access network (CRAN), wireless sensor network (WSN), and so forth are being operated at lower transmission power with lightweight hardware. Hence, for such type of power constraint networks, proposed PLKG system with NLPE can be proven a perfect security solution.

Average Contiguous Duration—A Novel Metric for Characterizing Wireless Fading Channels

We define the average contiguous duration (ACD) of the received fading signal as the average time duration during which the signal envelope contiguously remains within a bounded amplitude interval. Also, the multi-interval ACD or L-ACD function is defined as the set of ACD values for L non-overlapping amplitude-intervals whose union spans the received envelope's amplitude range. We derive closed-form expressions of the ACD for Rayleigh, Rice, and Nakagami- m fading signals, which are widely analyzed in the literature. The derived expressions hold practical significance for several signal processing applications such as non-uniform quantization of channel samples for secret key generation (SKG) in physical layer security (PLS) techniques. The well-known channel fading metric of average fade duration (AFD) is shown as a special case of the proposed ACD metric and the proposed theoretical analysis is validated by simulations.

Novel channel-hopping pattern-based wireless IoT networks in smart cities for reducing multi-access interference and jamming attacks

In smart cities, the Internet-of-Thing (IoT) provides an enabling communication infrastructure to support tremendous amount of data exchange. Most IoT applications, e.g., wireless local area network, Bluetooth and so forth, utilize the channel-hopping scheme to suppress the transmission security threats. In this paper, to reduce the mutual interference and external jamming attacks, multiple novel channel-hopping patterns, i.e., traditional no-hit-zone (NHZ) hopping pattern and generalized NHZ hopping pattern, are introduced to suit to IoT networks. Particularly the design of probabilistic hopping pattern is first proposed, which has the various usage probabilities with regard to various channels. The properties of these hopping patterns are investigated by the step-to-step examples. Then, the error-rate performance of the multi-node IoT systems adopting these hopping patterns in the presence of jamming attacks is comprehensively analyzed. The extensive simulations show that the traditional/generalized NHZ hopping patterns are in favor of combating the mutual interference but with the limited capability of reducing jamming attacks, while the probabilistic hopping pattern possesses the opposite feature, that is, it has the predominant merit in suppressing jamming attacks. Thus, the novel channel-hopping pattern-based IoT could provide the secure transmission for communication applications in smart cities. Note that, as the physical-layer security technique, the channel-hopping patterns investigated in this paper are convenient to integrate with the security policies implemented in upper layers (e.g., encryption, authentication and so forth).

Multi-cell, Multi-user, and Multi-carrier Secure Communication Using Non-Orthogonal Signals’ Superposition with Dual-Transmission for IoT in 6G and Beyond

Considering the advancements of the internet of things (IoT) in 6G and beyond communications, data transmission security in IoT devices has received extensive interest because of their significant features, such as low computational complexity, led by low power requirements. In such devices, the conventional cryptographic techniques may fail to provide secure communication. To fight this drawback, physical layer security (PLS) has remarkable potential to provide security solutions suitable for such applications. In this work, a highly effective PLS technique is proposed for providing secure communication against external and internal eavesdroppers in a downlink multi-cell, multi-user, and multi-carrier IoT communication system. In our proposed system, we considered two base stations, where each base station uses a single radio frequency (RF) chain to link two antennas that are used for the transmission of data. Further, we transmit the data in two rounds, and each round of transmission occurs through a single active antenna of each base station. A different antenna is used for each round of transmission to communicate with two single antenna IoT devices/users in the presence of a passive eavesdropper. In the proposed algorithm, frequency selective channel-based pre-coder matrices and the dual transmission approach are jointly employed. The dual-transmission is performed simultaneously from two base stations to provide security against internal and external eavesdroppers. The proposed system is suitable for IoT-based applications. Also, the potential capabilities of our proposed algorithm are proved by extensive mathematical and simulation analysis.

Machine learning-based security-aware spatial modulation for heterogeneous radio-optical networks

In this article, we propose a physical layer security (PLS) technique, namely security-aware spatial modulation (SA-SM), in a multiple-input multiple-output-based heterogeneous network, wherein both optical wireless communications and radio-frequency (RF) technologies coexist. In SA-SM, the time-domain signal is altered prior to transmission using a key at the physical layer for combating eavesdropping. Unlike conventional PLS techniques, SA-SM does not rely on channel characteristics for securing the information, as its perception is self-imposed, which allows its adoption in radio-optical networks. Additionally, a novel periodical key selection algorithm is proposed. Instead of having multiple keys stored in the nodes, by using off-the-shelf and low-complexity machine learning (ML) methods, including a support vector machine, logistic regression and a single-layer neural network, SA-SM nodes can estimate the used key. Results show that a positive secrecy capacity can be achieved for both the RF and optical links by using 1000 different keys, with a minimal signal-to-noise ratio penalty of less than 5 dB for the legitimate user using SA-SM versus conventional transmission at a bit-error-rate of 10−4. The analysis also includes computational time and classification accuracy evaluation of the various proposed ML techniques using different hardware architectures.

Optimal Subset Size Analysis of Randomized Analog Beamforming Using Uniform Planar Arrays in mmWave Networks

Assuming millimeter wave (mmWave) systems, we consider an analog beamforming-based physical layer security (PLS) technique, which has considerably lower complexity compared to the digital beamforming-based PLS. Motivated by the limitations of the related prior arts assuming a uniform linear array (ULA), we employ a uniform planar array (UPA) to take advantage of both azimuth and elevation domains to realize three-dimensional (3D) beamforming. Also, in contrast to the approximate analysis on the secrecy rate (SR) in the existing studies, we derive the exact SR without any approximation. Based on this analysis, we analyze the optimal size of random antenna subset, which is the key parameter to maximize the SR.

Hybrid Directional Modulation and Beamforming for Physical Layer Security Improvement Through 4-D Antenna Arrays

The physical layer security techniques have made great progress in the past few years. The essential idea of physical layer transmission is to maximize the randomness of undesired channels. The 4-D antenna arrays formed by introducing time as the fourth controlling degree of freedom can be used to regulate the radiated fields in space, time, and frequency domains simultaneously. Thus, 4-D antenna arrays are an effective carrier for achieving physical layer secure transmission. However, the traditional secure transmission approach based on 4-D antenna arrays always inevitably leads to high sidelobe levels (SLLs) of radiated power or less channel randomness. Aimed at this problem, a novel physical layer secure transmission approach based on 4-D antenna arrays is proposed, which combines the advantages of traditional phased arrays and 4-D arrays. The approach can be used to reduce the SLL of radiated power and improve the channel randomness by optimizing the time sequences and static amplitude weighting. Moreover, the signal distortion caused by time modulation can be compensated in the desired direction by premodulating the transmitted signals. Both the numerical and experimental results demonstrate the effectiveness of the proposed approach.

Mode Selection and Cooperative Jamming for Covert Communication in D2D Underlaid UAV Networks

The integration of unmanned aerial vehicle (UAV) networks and device-to-device (D2D) communications is expected to provide ubiquitous connectivity and high-speed rates for sensitive information transmission in future wireless networks. However, the traditional cryptography and physical layer security techniques still cannot prevent adversaries from knowing the existence of information transmission such that they further launch attacks on transmitters and receivers. Covert communication can offer an even stronger level of security via hiding the information transmission process of wireless networks. In this article, we first integrate D2D communications into UAV networks, and then investigate the fundamental issues of mode selection and cooperative jamming for covert communication in such networks, aiming to provide a powerful security solution to support widespread securi-ty-sensitive applications of such networks. To this end, we propose two promising D2D underlaid UAV network architectures, whereby each UAV acts as either a flying BS or an aerial UE. Then, we propose a covert communication strategy by combining mode selection and cooperative jamming, where mode selection allows each user equipment to adaptively switch between half-du-plex and full-duplex communication modes, and cooperative jamming means that idle D2D pairs inject interference to confuse adversaries. The goal of the proposed strategy is to enhance covert capacity performance (i.e., the maximum channel rate) while maintaining a high detection error probability at adversaries in the promising network architectures. Numerical results are presented to evaluate our strategy of mode selection and cooperative jamming, and to illustrate performance gains in terms of covert capacity and detection error probability in these two network architectures. Finally, a vision is discussed for our future research in D2D underlaid UAV networks.

An enhanced indoor visible light communication physical‐layer security scheme for 5G networks: Survey, security challenges, and channel analysis secrecy performance

SummaryVisible light communication (VLC) is considered to be a great replacement or complement to existing radio frequency networks to provide the future fifth‐generation (5G) wireless technology with higher data rates for indoor connectivity, which alleviates the traffic demand. Therefore, many issues emerged regarding the security in 5G networks as human safety is at risk. This work presents a comprehensive study on the physical‐layer security (PLS) and solutions in 5G networks, specifically, the security of VLC technology as one of the core PLS solutions for 5G future wireless networks. Furthermore, VLC threats and PLS solutions are extensively investigated. Based on our study, we propose a new indoor VLC secure model to enhance the secrecy performance in VLC networks using a combination of multiple PLS techniques to achieve this aim as beamforming, secure communication zones, and friendly jamming. The simulation results with respect to the received optical power and signal‐to‐noise ratio (SNR) prove that the proposed indoor VLC model can improve the secrecy performance. As the user's SNR exceeded 100 dB and optical received power reached 15 mW, the malicious user's SNR barely reached 30 dB with a 4‐μW received power outside the target zone increasing his interference level. Finally, future research directions in VLC security are outlined to encourage future research.

Secure Millimeter-Wave Ad Hoc Communications Using Physical Layer Security

Millimeter-wave (mmWave) communications are highly promising to improve the capacity of modern wireless networks, while the physical layer security (PLS) techniques hold great potential to enhance the critical secrecy performance therein. By carefully exploiting the significant signal difference between the Non-Light-of-Sight (NLoS) and Line-of-Sight (LoS) mmWave links, this paper proposes a Sight-based Cooperative Jamming (SCJ) scheme to improve the PLS performance of mmWave ad hoc communications. In this scheme, each potential jammer that has no LoS link to its nearest receiver but may have LoS links to eavesdroppers is selected with a certain probability to generate artificial noise such that channel advantages at legitimate receivers can be achieved. For performance modeling of the new jamming scheme, novel and efficient theoretical approximation approaches are firstly developed to enable the challenging issue of interference distribution modeling to be tackled, and then a theoretical framework based on stochastic geometry is proposed to capture the secrecy transmission capacity behavior under the SCJ scheme. Finally, extensive numerical results are provided to illustrate the SCJ scheme under various network scenarios.

On Quantization for Secret Key Generation From Wireless Channel Samples

Physical layer security (PLS) techniques hold promise for augmenting secure communications in the 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> generation of mobile wireless networks. Secret key generation (SKG) is a PLS technique which exploits the wireless propagation channel's randomness to generate symmetric key bits for information encryption and decryption. This work proposes symmetric key generation based on non-uniform quantization of the received signal strength (RSS) samples of a Nakagami-$m$ fading channel. The proposed strategy for non-uniform quantization for SKG aims to set quantization thresholds for maximal key randomness and high values of key generation rate (KGR) and key agreement probability (KAP). Finally, a framework is proposed to use single node RSS measurements, readily available in the literature, to generate RSS samples at the other link end. This framework facilitates the testing of new SKG algorithms that require simultaneous RSS measurements by the legitimate nodes, which are not readily available in the open literature. The effectiveness of the proposed SKG scheme is validated through Monte Carlo methods and the National Institute of Standards and Technology (NIST) test suite for assessing the randomness of the generated key sequence.

An Advanced Non-Orthogonal Multiple Access Security Technique for Future Wireless Communication Networks

The future wireless communication systems demand much more enhanced security and reliability compared to currently deployed systems. In this work, we propose a much simpler yet more efficient physical layer security (PLS) technique for achieving reliable and secure communication in the multiple-input single-output non-orthogonal multiple access (MISO-NOMA) systems. This system is capable of providing enhanced confidential communication as well as inter-user interference cancellation without using the successive interference cancellation (SIC) method. The conventional NOMA was previously adopted under the name of multi-user superposition transmission (MUST) in release 13 of 3GPP but recently excluded from 3GPP-release 17 due to its performance degradation. In this work, we analyze the drawbacks in conventional NOMA and present a new kind of NOMA with more improved performance metrics. The proposed algorithm combines the benefit of pre-coder matrices with simultaneous transmission using antenna diversity to provide simple, reliable, and secure communication without complex processing at the receivers in downlink scenarios. The effectiveness of the proposed algorithm is verified and proven by extensive analysis and numerical simulations.

Secrecy transmission capacity in mobile ad hoc networks with security‐aware Aloha protocol

Mobile ad hoc networks (MANETs) represent a class of important network models for supporting various critical applications, while the security breach due to eavesdropping attacks has been a critical issue. This study investigates the security issue of MANETs from the perspective of physical layer security (PLS). In particular, by combining PLS techniques [e.g. artificial noise (AN) injection and Secrecy Guard zoNe (SGN)] and the conventional Aloha protocol, the authors first propose an AN-based Aloha protocol and a SGN-based Aloha protocol to ensure secure medium access for legitimate transmitters. In the AN-based Aloha protocol, all potential transmitters are allowed to be active and each active transmitter injects AN into its transmitted signals to confuse eavesdroppers. In the SGN-based protocol, each potential transmitter has an SGN, a circle centred at itself, and only the potential transmitters whose SGN contains no eavesdroppers are allowed to be active. To understand the security performances of the proposed security-aware Aloha protocols, the authors then apply tools from Stochastic Geometry to analyse the secrecy transmission capacity (STC) performances of MANETs under both protocols. Finally, the authors provide simulation/numerical results to corroborate the proposed theoretical analysis and also to show the impacts of network parameters on the STC performances.

Physical Layer Security Enhancement Using Artificial Noise in Cellular Vehicle-to-Everything (C-V2X) Networks

The secure transmission of confidential information in cellular vehicle-to-everything (C-V2X) communication networks is vitally important for user's personal safety. However, for C-V2X there have not been much studies on the physical layer security (PLS). Since artificial noise (AN) and secure beamforming are popular PLS techniques for cellular communications, in this paper we investigate the potential of these PLS techniques for enhancing the security of C-V2X networks. In particular, leveraging stochastic geometry, we study the PLS of an AN assisted C-V2X network, where the locations of legitimate vehicular nodes, malicious vehicular nodes and road side units (RSUs) are modeled by Cox processes driven by a common Poisson line process (PLP), and the locations of cellular base stations (BSs) are modeled by a two-dimensional (2D) Poisson point process (PPP). Based on the maximum signal-to-interference-ratio (SIR) association scheme, we calculate the coverage probability of the network. We also derive bounds on the secrecy probability, which are validated by simulation results. Moreover, we obtain an analytical result of the effective secrecy throughput for characterizing the reliability and security of wiretap channels. Simulation results are given to validate the analytical result, and provide interesting insights into the impact of network parameters on the achievable secrecy performance. Simulation results show that a larger array antenna can provide a better robustness of the secure transmission strategy, and the optimal power allocation ratio between confidential information and AN remains almost unchanged for different numbers of antennas.

Survey on physical layer security for 5G wireless networks

Physical layer security is a promising approach that can benefit traditional encryption methods. The idea of physical layer security is to take advantage of the propagation medium’s features and impairments to ensure secure communication in the physical layer. This work introduces a comprehensive review of the main information-theoretic metrics used to measure the secrecy performance in physical layer security. Furthermore, a theoretical framework related to the most commonly used physical layer security techniques to improve secrecy performance is provided. Finally, our work surveys physical layer security research over several enabling 5G technologies, such as massive multiple-input multiple-output, millimeter-wave communications, heterogeneous networks, non-orthogonal multiple access, and full-duplex. We also include the key concepts of each of the technologies mentioned above. Also identified are future fields of research and technical challenges of physical layer security.