Authentication & Authorization system

Im designing a application in .net and now im comming to the point when i have to decide what would be the best authentication method. The applicati开发者_运维技巧on has one public Web site Client and a private backoffice WPF both working with an WCF layer. I would like to be able to allo the users logging from facebook and other external sites but without losing the ASP.net membership capabilities for WCF. My question is what would be the best approach to develop this feature?

Any answer are welcome.

Thanks in advance

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You should explore Windows Identity Foundation and OAuth and the respective .NET library oauth-dot-net.