Silverlight out of browser offline forms authentication

I'm building an app which is subscription based, users can login to a website an use it as they please. I would also like them to have the option to work with it outside of the browser and even offline. The app itself is not dependent on online resources, only the authentication is done via forms authentication.

What would be the best way for me to make offline authent开发者_StackOverflow中文版ication possible?

You could consider using WCF RIA Services for authorization and authentication with your own membership system. Here is a brief example.