A Subscriber Ientity Module (SIM) is part of a removable smart card ICC (Integrated Circuit Card), also known as SIM Cards, for mobile cellular telephony devices such as mobile computers and mobile phones. SIM cards securely store the service-subscriber key (IMSI) used to identify a subscriber. The SIM card allows users to change phones by simply removing the SIM card from one mobile phone and inserting it into another mobile phone or broadband telephony device.