Physical Layer Key Generation (PKG) has evolved as a promising technique to circumvent the problems faced by the classical symmetric key production schemes. It exploits channel reciprocity and spatial decorrelation provided by wireless medium. This paper systematically reviews the evolution of PKG technologies, discussing their working principles, performance metrics, and implementations under various scenarios such as slow-fading channels, low SNR, and multi-user environments. With recent advancements introduced—intelligent reflecting surfaces (RIS/STAR-RIS), optimization powered by AI/ML, and their integration with massive MIMO and terahertz communications—chaos, robustness, and scalability enhancements are investigated. Further exploration involves application domains from IoT and healthcare to Industry 4.0 and 6G networks, this focus shifting from proof of feasibility to full-fledged implementation. The concluded findings show that PKG is inclined to become a key security primitive for next-generation wireless systems to enjoin lightweight and efficient friendly key management schemes.
Physical Layer Key Generation (PKG) has evolved as a promising technique to circumvent the problems faced by the classical symmetric key production schemes. It exploits channel reciprocity and spatial decorrelation provided by wireless medium. This paper systematically reviews the evolution of PKG technologies, discussing their working principles, performance metrics, and implementations under various scenarios such as slow-fading channels, low SNR, and multi-user environments. With recent advancements introduced—intelligent reflecting surfaces (RIS/STAR-RIS), optimization powered by AI/ML, and their integration with massive MIMO and terahertz communications—chaos, robustness, and scalability enhancements are investigated. Further exploration involves application domains from IoT and healthcare to Industry 4.0 and 6G networks, this focus shifting from proof of feasibility to full-fledged implementation. The concluded findings show that PKG is inclined to become a key security primitive for next-generation wireless systems to enjoin lightweight and efficient friendly key management schemes.
As the development of next-generation (NextG) communication networks continues, tremendous devices are accessing the network and the amount of information is exploding. However, with the increase of sensitive data that requires confidentiality to be transmitted and stored in the network, wireless network security risks are further amplified. Physical-layer key generation (PKG) has received extensive attention in security research due to its solid information-theoretic security proof, ease of implementation, and low cost. Nevertheless, the applications of PKG in the NextG networks are still in the preliminary exploration stage. Therefore, we survey existing research and discuss (1) the performance advantages of PKG compared to cryptography schemes, (2) the principles and processes of PKG, as well as research progresses in previous network environments, and (3) new application scenarios and development potential for PKG in NextG communication networks, particularly analyzing the effect and prospects of PKG in massive multiple-input multiple-output (MIMO), reconfigurable intelligent surfaces (RISs), artificial intelligence (AI) enabled networks, integrated space-air-ground network, and quantum communication. Moreover, we summarize open issues and provide new insights into the development trends of PKG in NextG networks.
While Physical Layer Key Generation (PKG) offers lightweight security for 6G IoT, channel non-reciprocity in FDD massive MIMO degrades key consistency. This paper presents a comprehensive review of Physical Layer Key Generation (PKG) techniques within Frequency Division Duplex (FDD) massive MIMO systems. While PKG leverages the inherent randomness of wireless channels to establish lightweight security for communication nodes, FDD systems pose a significant challenge. The separated uplink and downlink bands produce non-reciprocal fast-fading channel responses, which inherently degrade the consistency of keys generated from instantaneous channel state information (CSI). To address this, this study categorizes existing methodologies into three primary routes: stable propagation feature extraction, intelligent feature mapping, and system engineering optimization. It examines their mechanisms across the angle, beam, and statistical covariance domains, comparing representative schemes in terms of Key Disagreement Rate (KDR), overhead, and computational complexity. Ultimately, future research must integrate physical priors with data-driven models to ensure robust security in practical 6G networks.
The diverse application scenarios envisioned for sixth generation (6G) are characterized by the deep integration of sensing and ubiquitous connectivity, which imposes unprecedentedly stringent security requirements. However, due to the open nature of wireless channels, mobile communications systems always face severe information security threats such as falsification, spoofing, interception, and repudiation. Cryptography-based symmetric and asymmetric encryption techniques remain mainstream solutions for information protection. Symmetric encryption is efficient and secure for legitimate users but suffers from key-distribution difficulties over open wireless channels, whereas asymmetric encryption resolves this problem but faces increasing risks from quantum computing due to its reliance on structured mathematical hardness assumptions. In response to these limitations, physical layer security (PLS) has gained a great deal of research attention as a powerful security component that leverages the features of varying wireless channels. Existing PLS schemes can be broadly classified into two categories. The first one takes advantage of the legitimate link’s opportunistic channel-quality superiority over or different spatial-domain directions from the attacking link, which still faces many practical implementation difficulties. The second category is termed physical-layer key generation (PLKG). It extracts the unique features of the legitimate link’s channel variation, which is often reciprocal, as the source of secret key generation and therefore can naturally implement secure key distribution tasks. This advantage no doubt injects new vigor to symmetric encryption as a stronger protection approach. Following this trend, we in this paper concentrate on the PLKG techniques. Specifically, we present a comprehensive overview on existing PLKG schemes, discussing diverse secret key generation and reconciliation methods. We further investigate the model-driven and deep-learning-based approaches tailored for the scenario with imperfect channel reciprocity between the sender and receiver. After comprehensively reviewing major existing schemes, we further discuss a recently proposed PLKG design based on codeword reconstruction, which makes use of the strong error-correcting capability of the forward-error-correction (FEC) codes to effectively implement secure and consistent secret key generation between the legitimate sender and receiver. Finally, we share our opinions on the unsolved challenges and potential research directions dedicated to PLKG toward meeting the security requirements of 6G.
With the burgeoning internet of things (IoT), securing communication becomes paramount. Traditional cryptography does not meet computational needs and brute-force attacks. This review explores the state-of-the-art physical layer secret key generation (PLKG) that takes advantage of the inherent reciprocity and randomness of wireless channels. We investigate cutting-edge techniques such as feature extraction networks, domain adversarial training, and deep learning-based approaches, evaluating their effects on the security and efficiency of key generation. In addition to these methods, the review addresses real-world challenges such as multi-user scenarios, reconciliation overhead, and inconsistent channel measurement. We believe that improved key generation rates and security can be achieved through the use of millimeter wave technology and full-duplex communication. To strengthen the robustness of key generation, the paper concludes by suggesting future directions, such as incorporating more random sources, such as physiological signals and sensor data. This comprehensive overview offers deep insights into the state-of-the-art and paves the way for reliable communication in ever more complicated IoT settings.
The fifth generation (5G) and beyond wireless communications will transform many exciting applications and trigger massive data connections with private, confidential, and sensitive information. The security of wireless communications is conventionally established by cryptographic schemes and protocols in which the secret key distribution is one of the essential primitives. However, traditional cryptography-based key distribution protocols might be challenged in the 5G and beyond communications because of special features such as device-to-device and heterogeneous communications, and ultra-low latency requirements. Channel reciprocity-based key generation (CRKG) is an emerging physical layer-based technique to establish secret keys between devices. This article reviews CRKG when the 5G and beyond networks employ three candidate technologies: duplex modes, massive multiple-input multiple-output (MIMO) and mmWave communications. We identify the opportunities and challenges for CRKG and provide corresponding solutions. To further demonstrate the feasibility of CRKG in practical communication systems, we overview existing prototypes with different IoT protocols and examine their performance in real-world environments. This article shows the feasibility and promising performances of CRKG with the potential to be commercialized.
The evolution from 5G to 6G wireless networks is driving a fundamental transformation in encryption technologies. While 5G networks primarily rely on advanced classical cryptography, including AES, ECC, and RSA, emerging applications such as IoT, e-healthcare, and ultra-reliable low-latency communications demand lightweight, hybrid, and context-aware security schemes. The advent of quantum computing poses significant threats to classical cryptosystems, motivating the integration of quantum-resistant security techniques, including post-quantum cryptography (PQC), quantum key distribution (QKD), and physical layer security (PLS) in 6G networks. This review synthesizes recent research on classical, hybrid, and quantum-resistant security techniques, highlighting the shift toward multi-layered and adaptive security frameworks. A comparative analysis of PLS in 5G and 6G illustrates its transition from a complementary role to a core security mechanism, especially in ultra-low-latency, massive connectivity, and heterogeneous environments. Finally, open research questions and standardization challenges are discussed, emphasizing the need for scalable, energy-efficient, and interoperable security solutions for next-generation wireless networks.