whats the best way to secure content on another web site / subdomain of a public facing web site?

Question

I have a public facing web site living at www.somedomain.com. This web site renders pages with links to images that live at photos.somedomain.com. All users that view images on www.somedomain.com must be authenticated with forms authentication and they are authenticated by the asp.net membership provider running in the context of the web site at www.somedomain.com.

How can I implement security on photos.somedomain.com, such that ONLY authenticated users of www.somedomain.com are able to access images living at photos.somedomain.com?

Answer 1

If the applications are so closely related that they share an authentication system, would it not be better to merge the 2 applications into one single application?