CRM 4.0 Authentication Using XRM

Hi

I am trying to authenticate users with CRM, but I am having difficulties and truthfully with the myriad of suggestions on the topic, I am having difficulties finding a path that truly works. The following is what I am trying to accomplish:

I have a ASP.NET MVC 5 application. I am using xRM to manipulate CRM's data. I like the ease of LINQ it allows me. I am using Forms authentication. My plan is to authenticate the user and use the credentials to build the connection for xRM. That is, unless someone knows how to authenticate and create a security token using a xRm connection.

Any help would be deeply appreciate it.

Thanks

Hector