How To Handle User Login/Registration?

I have an iPhone app that uses core data. I want to add account management to this app for backup and social reasons. What is the easiest way to handle account registration and login? Will I need to create a PHP script or create an XML/J开发者_如何学CSON file?

Any advice would be great. I have no idea what to do (I'm only familiar with Cocoa Touch).

Edit:

I think I will be going with a twitter login. Hmm, so if I do a twitter login, when the user signs in, their account data will be loaded into my database? Or something similar? I think I still need my own server because if a user signs in from another device, their data should show up there too.

From a usability standpoint, it would be best to use login's from Facebook or Twitter as the user will generally prefer to have a single login. They make sdk's for this, and it also reduces the amount of work you have to do on your end to maintain accounts. If the account is essential to your app then explore other options, but if it is just social, as you mentioned above, don't reinvent the wheel.