Issue with authenticating user

Hello Everyone,

Thank You for responding to my previous posts.

I am presently working on a Web Application which would have single sign on.

Here is the scenario:

Web Application is the www.someotherwebsite.com which is external Web Application.

My Web Application will receive encrypted string(which is a key) in query string which will indicate the user is authenticated on their www.someotherwebsite.com.

Now the question is can I use the Form Authentication and Membership Profile in this scenario? If Yes, how to implment it? If No, what is the alternative?

Also if some can help me with forcefully setting Me.User.Identity.IsAuthenticated() to TRUE?

Thanks
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