getting the signed request from facebook authentication

Hi Guys

I am writing the mobile app for a web service where I am leveraging their existing backend URLs. As part of this service they use facebook for authentication. The backend URL expects both the FB access token, which I get using Ti.Facebook.getAccessToken(), and the signed request, as documented here on the facebook developers pages.

My question is how do I get this signed request? I have taken a simple approach ATM in using Ti.Facebook.createLoginButton(), can I get the signed request with this approach or do I need to get more complicated?

Thanks, Richard