Introducing IdentityServer4
Security Token Service (STS) is a critical component of token-based authentication. Other terms that you might encounter are identity provider or authorization server. It's a piece of software that generates and issues security tokens to client-side applications. Client-side applications redirect user verification to STS to handle it. The token is encrypted and signed to ensure that the token is protected from any tampering.
The encryption in the application uses a private key kept by the token service, while the public key for decrypting the token is shared with client-side applications. In this way, the client applications trust that the token came from the right token service. Standards for providing identity information, such as OpenID Connect, are used by token services.
When it comes to consuming token services, there are different options. You can use a pre-built service such as Active Directory Federation Services (ADFS) to build your...