http://support.apple.com/kb/ht5570 http://support.apple.com/kb/ht5570 > When you set up two-step verification, you register one or more trusted devices. A trus

http://support.apple.com/kb/ht5570 http://support.apple.com/kb/ht5570 > When you set up two-step verification, you register one or more trusted devices. A trusted device is a device you control that can receive 4-digit verification codes using either SMS or Find My iPhone. You're required to provide at least one SMS capable phone number. > Then, any time you sign in to manage your Apple ID at My Apple ID or make an iTunes, App Store, or iBooks Store purchase from a new device, you'll need to verify your identity by entering both your password and a 4-digit verification code, as shown below.