A SIM card or SIM is an integrated circuit (IC) in the range of a 25 MHz 32 bit CPU, and 256 KB of NVM. SIMs are intended to securely store an international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephone devices. SIMs are also able to run apps and to store arbitrary information like address book contact information, and may be protected using a PIN code to prevent unauthorized use.
