Adding Security Layer to OData Service

Im creating an Odata service th开发者_StackOverflow中文版at is being exposed to an IPhone application and potentially other receivers. Im just wondering what is the best method for adding security to the Odata service so all data requests to the Odata provider are authenticated?

Thanks in advance

---

There's a great series of posts about auth over OData services here: http://blogs.msdn.com/b/astoriateam/archive/tags/authentication/