MicroSIMs come with a couple extra features: allow for multiple simultaneous applications accessing the card through logical channels; introduce mutual authentication as a way to eliminate carrier spoofing by allowing the SIM card to authenticate the cell tower to which it is connecting; add a new PIN protection with hierarchical PIN management with a universal PIN, an application PIN and a local PIN; expand the phonebook storage of the SIM card with entries for email, second name, and groups. Why does the iPhone HD use a MicroSIM just like iPad|The iPhone User Guide
