https://www.c-sharpcorner.com/article/securing-your-Asp-Net-web-applications/
To configure Secure Sockets Layer (SSL) for a site in IIS 7, you could follow these steps.
Get an appropriate certificate.Create an HTTPS binding on a site.Test by making a request to the site.Optionally configure SSL options, that is, by making SSL a requirement.
https://www.c-sharpcorner.com/UploadFile/8ef97c/web-service-in-Asp-Net-security-by-soap-authentication-pa/
1.**HMAC Authentication**
This security mechanism is common in public APIs and is relatively easy to implement. The client or application that wants to access your service will need an API Key and a Secret Key from you as the service owner. These keys are usually randomly generated strings and is given to the client beforehand. API Keys are unique to each client/application. Both the client and server will hold the API Key and Secret Key.
**2.Digital Signature
Digital signature relies on private-public key pair is a useful mechanism for securing server to server communication. It works by signing the message content with a private key to produce a security signature that can be verified using the corresponding public key (certificate). A key pair is usually provided by a certificate authority.
**3.OAuth**
OAuth is popular security mechanism that is widely used for user authentication. Similar to how a logged in session works on a website, OAuth requires the client user to “login” to the Web API before allowing access to the rest of the service.
Could you please add more details? Are you asking how to implement authentication or authorization in web application?