I. INTRODUCTION  
A. Review methodology  
B. Contributions  
C. Structure of the paper  

ACRONYMS  

II. RELATED WORK AND OUR SURVEY POSITION  

III. SECURITY ISSUES AND THE EVOLUTION OF SECURITY ARCHITECTURE IN LEGACY MOBILE NETWORKS  
A. 1G, 2G, 3G - Security issues of phased-out and phasing-out networks  
B. Featured upgrades in 5G security  
C. Security vulnerabilities of 5G  
D. Network deployment strategies’ impact on security architecture and security transition  

IV. 6G NETWORK VISION AND POTENTIAL CHANGES OF ITS SECURITY ARCHITECTURE  
A. 6G applications, network vision, and potential security threats that impact on 6G security and privacy  
B. Overview of several security and privacy issues on typical 6G applications: finding the origin of the issues  
C. 6G for the expectation of the Internet of Everything and security evolution  
D. Vision of 6G security architecture and potential changes  
E. Summary of lessons learned from key possible changes of 6G security  

V. SECURITY IN THE PHYSICAL LAYER  
A. Security in 6G mmWave communications  
B. Security in 6G Large Intelligent Surface  
C. Security in NOMA for 6G massive connectivity  
D. Security in 6G Terahertz communications  
E. Security in 6G VLC communications  
F. Security in 6G Molecular communications  
G. Other prospective technologies for 6G physical layer security  
H. Summary of lessons learned from physical layer security  

VI. SECURITY IN THE CONNECTION LAYER  
A. Enhanced Security Edge Protection Proxy (SEPP) for securing interconnect between 6G networks: Roaming Security  
B. Blockchain and distributed ledger technologies for a vision of 6G trust networks  
C. SD-WAN security: 6G network management control  
D. Deep slicing and Open RAN for 6G network security isolation  
E. Next-generation firewalls/intrusion detection for 6G network endpoint and multi-access edge security  
F. Summary of lessons learned from connection layer security  

VII. SECURITY IN THE SERVICE LAYER  
A. 6G application authentication: Distributed PKI and blockchain-based PKI  
B. Using service access authentication (6G AKA) for application authentication  
C. 6G biometric authentication for 6G-enabled IoT and implantable devices  
D. OAuth 3.0: new authorization protocol for 6G applications and network function services  
E. Quantum homomorphic encryption for secure computation  
F. Liquid software security: a step to 6G platform-agnostic security  
G. AI-empowered security-as-a-service transition for 6G “Service Everywhere” architecture  
H. Summary of lessons learned from service layer security  

VIII. ARTIFICIAL INTELLIGENCE’S IMPACT ON 6G SECURITY  
A. AI as a guardian: AI for enhancing 6G security  
B. AI as a target: Security attacks against 6G AI-empowered engines and defense approaches  
C. AI as a weapon: Ethical AI/Super intelligent AI/AI Regulation  
D. Summary of lessons learned from AI’s impact on 6G security  

IX. PRIVACY CHALLENGES AND PRESERVATION APPROACHES  
A. Why data privacy matters in 6G  
B. State-of-the-art privacy preservation techniques and vision for 6G  
C. Privacy challenges  
D. Summary of lessons learned from privacy enhancing technologies  

X. DISCUSSION ON FUTURE RESEARCH DIRECTIONS AND OPEN ISSUES  
A. Future research directions for 6G security and privacy  
B. Open challenges and issues  

XI. CONCLUSION