A lot of different services on the Internet offer ways for their users to authenticate with third-party applications. In this recipe, we will look at implementing a custom OpenID authentication provider by using Steam as an example.

Steam is a platform for game distribution and social gaming. Like a lot of social, Internet-based applications, you can add friends, see their status, and message each other. Steam also keeps track of game statistics for certain games. If you were creating a web application centered around computer games or with a large cross-over audience, adding functionality that would allow your users to sign in with their Steam account might be a welcome feature.