<p>Fifth-generation and beyond (5G and xG) wireless networks are envisioned to meet the requirements of various vertical applications that require higher traffic throughput, ultra-massive connectivity, extremely low latency, and high quality of service. Disruptive technologies, such as massive multiple-input multiple-output, millimeter wave, and multiple access are being deployed to meet these requirements. However, the deployment of these technologies poses several challenges, including the lack of network transparency, management decentralization, and reliability. In addition, the heterogeneity of these networks raises security concerns, particularly, confidentiality, privacy, and trustworthiness. Typically, networks rely on encryption techniques at higher layers to ensure  security and privacy. However, due to the emergence of novel computing paradigms, such as quantum computing, traditional security approaches are no longer sufficient to protect over-the-air communications. Therefore, 5G/xG networks must consider smarter and more efficient security techniques to operate seamlessly and efficiently. Within this context, physical layer security (PLS) and blockchain represent promising solutions to complement existing methods. By exploiting the characteristics of wireless links, PLS can enhance the security of wireless communications, while blockchain can guarantee the decentralization, integrity, and trustworthiness of networks. Motivated by these technological advancements, this paper provides an in-depth review of the existing literature on PLS and blockchain. Then, for the first time, we present a framework for the integration of PLS with blockchain in 5G/xG  systems. We begin by providing a thorough discussion about the potential of PLS and blockchain for 5G/xG systems. Next, we present our vision of a cross-layer architecture that leverages both PLS and blockchain in 5G/xG networks. Finally, we identify related challenges and open issues and shed light on future research directions.</p> <p><br></p>

<p>Fifth-generation and beyond (5G and xG) wireless networks are envisioned to meet the requirements of various vertical applications that require higher traffic throughput, ultra-massive connectivity, extremely low latency, and high quality of service. Disruptive technologies, such as massive multiple-input multiple-output, millimeter wave, and multiple access are being deployed to meet these requirements. However, the deployment of these technologies poses several challenges, including the lack of network transparency, management decentralization, and reliability. In addition, the heterogeneity of these networks raises security concerns, particularly, confidentiality, privacy, and trustworthiness. Typically, networks rely on encryption techniques at higher layers to ensure  security and privacy. However, due to the emergence of novel computing paradigms, such as quantum computing, traditional security approaches are no longer sufficient to protect over-the-air communications. Therefore, 5G/xG networks must consider smarter and more efficient security techniques to operate seamlessly and efficiently. Within this context, physical layer security (PLS) and blockchain represent promising solutions to complement existing methods. By exploiting the characteristics of wireless links, PLS can enhance the security of wireless communications, while blockchain can guarantee the decentralization, integrity, and trustworthiness of networks. Motivated by these technological advancements, this paper provides an in-depth review of the existing literature on PLS and blockchain. Then, for the first time, we present a framework for the integration of PLS with blockchain in 5G/xG  systems. We begin by providing a thorough discussion about the potential of PLS and blockchain for 5G/xG systems. Next, we present our vision of a cross-layer architecture that leverages both PLS and blockchain in 5G/xG networks. Finally, we identify related challenges and open issues and shed light on future research directions.</p> <p><br></p>