Why do OAuth packages in ASP.NET depend on Owin?

Question

There are multiple ways to secure a rest service like Basic authentication,API Key Authentication but OAuth is the most preferred ,I am new to Asp.Net and no nothing about Owin ,I have created a web Api project and now i want to secure it with OAuth 2.0 ,but all packages depend on Owin like Microsoft.Owin.Security.OAuth.Why do i actually need Owin to implement Oauth? Can't i simply implement OAuth in my project?