There are two different versions of the Auto-Key plug-in.  One version is sold individually, and the other version is included with purchases of Auto-Tune Pro.  Both versions have the exact same functionality, but some important differences detailed below:

Auto-Key (sold individually): This version does not require authorization with an iLok dongle, but can instead by authorized directly to your computer using the included Antares Central application.  This is a convenient option if you do not have an iLok dongle or account.

Auto-Key (included with Auto-Tune Pro):  This version requires authorization with an iLok dongle and an Auto-Tune Pro iLok license.  If you purchase Auto-Tune Pro and install it on your computer, Auto-Key will automatically be installed alongside Auto-Tune Pro.  This option may be preferable if you already have an iLok dongle and account, and also wish to purchase Auto-Tune Pro.