SIM-Subscriber Identity Module
The terms SIM, smart card, and UICC have an unfortunate tendency to be used interchangeably. The UICC is hardware. A SIM is a software application. Generally speaking a smart card is a UICC running a SIM as well as possibly other applications.
SIM is actually just an application running on a smartcard. A given card could contain multiple SIM’s, allowing, for instance, a given phone to be used on multiple networks.
A typical SIM contains several categories of information. One is the actual identity of the card itself. The SIM needs to have a unique identity to the network. This allows the network to identify what sources the subscriber is entitled to, billing information, etc. A second category relates to the actual operation of the device. Information such as the last number called, or the length of the phone call can be stored. A third category of information is personalized information. Phonebooks or calendars fall into this category.
Uses of SIMs
SIM cards can be used in any kind of device or situation where there is a need to authenticate the identity of a user. They are particularly useful when there is a need or desire to provide different types or levels of service to many users who have different configurations.
The primary use of SIM cards in the United States is in cell phones. There are other uses as well. The US military issues smart cards as identification to its personnel. These cards are used to allow users to log into computers.
Europe has seen a wider use of these cards. The credit and debit card industry has integrated this technology in their cards for years. Similarly, a number of European phone companies have used these as phone cards to use in public telephones. The card companies in the United States have evidently not seen enough fraud to have a business justification to switch to this technology. There is some speculation that American credit cards will use a future generation of the technology when the added robustness and security of the system will make more economic sense.