The 5G mobile system is a culmination of technological evolution of communication technologies, including IP based services, virtualization, the rise of smartphones, IoT and the convergence of wired and wireless networks. With the evolution of 5G mobile connectivity, its security mechanism needs to adapt to a wide range of users and technological shifts. This book provides a simplified view of 5G security, bridging the gap between complex technical standards and practical understanding. Technical topics covered in this book include: Primary and secondary authentications Slice authentications Application-oriented authentication and key management support called AKMA Non-3GPP access and converged wireline-wireless authentication Non-public network UAV USS authentication and authorization Variability in 5G security feature adoption As mobile networks have become an integral part of modern society and critical infrastructure, this book is a timely insight into how 5G security is structured, applied and shaped by the technological and regulatory forces.