ASP.NET - IdentityServer Integration

IdentityServer integration refers to connecting an ASP.NET Core application with IdentityServer to handle authentication and authorization in a centralized and secure way. Instead of managing login logic inside every application, IdentityServer acts as a single authority that verifies users and issues security tokens.

Purpose of IdentityServer
The main purpose of IdentityServer is to manage identities and access control for multiple applications. It authenticates users once and then allows trusted applications to access user information through tokens. This approach reduces duplicated security code and enforces consistent authentication rules across systems.

How Integration Works Conceptually
When an application integrates with IdentityServer, it redirects users to IdentityServer for login. After successful authentication, IdentityServer issues tokens that contain user identity and permission data. The application validates these tokens and decides what the user is allowed to access.

Token-Based Communication
IdentityServer uses industry standards like OAuth 2.0 and OpenID Connect. Tokens such as access tokens and identity tokens are issued after login. These tokens are sent with requests and are verified by the application without needing to contact IdentityServer every time.

Benefits for Applications
Integration improves security by isolating authentication logic in one place. Applications become simpler because they only need to validate tokens, not manage passwords or sessions. It also supports single sign-on, allowing users to log in once and access multiple applications seamlessly.

Why IdentityServer Is Used in Real Projects
IdentityServer is commonly used in enterprise systems, microservices and APIs where multiple applications share users. It supports scalable security architecture, centralized control and modern authentication standards, making it suitable for complex and growing systems.