I have a simple application, based of the "Utility Application" template. It retrieves a password-protected XML file (via NSXMLParser).

I want to allow the user to set a username and password in the "FlipsideView", how would I go about this?

I have the basics in place, the two UITextField boxes, the value of which gets set to a fixed value when the view loads (using the viewWillAppear method), and NSLog'd when the view is closed (the NSLog is just for testing, obviously, in the viewWillDisappear method)

How do I store the data? I've had a look at the Developer documentation, and it seems like I should be using NSUserDefaults..?

I agree with Ben. This is exactly what the Keychain is for.

I would not, under any circumstances simply store passwords in the defaults as dbr suggests. This is highly insecure. You're essentially storing your passwords in the open.

In addition to Apple's sample code, I also recommend Buzz Anderson's Keychain code: iPhone Keychain Code