[winstonwinston]

First time I enabled iCloud keychain when it was released in iOS 7, it asked for both user defined security code (4-pin at the time) and a verification phone number.

When you switch to a new device and want to pull iCloud keychain to a new device you need to provide your security code (pin) and additionally a verification code that they send to the phone number.

Nowdays I’m not sure what my security code even is, because it stopped asking for it on a new devices, since you can approve pulling iCloud keychain from another device.