What is the fundamental part of the security module in Spring?

The fundamental part of the security module in Spring is the AuthenticationManager interface and the associated authentication mechanism.

Main components:

• AuthenticationManager — responsible for verifying the user's identity.
• UserDetailsService — loads user data (login, password, roles).
• SecurityContext — stores information about the currently authenticated user.
• Security Filters — intercept requests and ensure access rights.

Spring Security is built around these components, providing authentication and authorization in the application. Access control and resource protection are implemented through them.