Subscriber Identity Module

A SIM card, also known as a subscriber identity module, is a subscriber identity module application on a smartcard that stores data for GSM/CDMA Cellular telephone subscribers. Such data includes user identity, network authorization data, personal security keys, contact lists and stored text messages.



A SIM is embedded into a removable SIM card, which can be transferred between different mobile devices. SIM cards were first made the same size as a credit card (85.60 mm × 53.98 mm × 0.76 mm). The development of physically-smaller mobile devices prompted the development of a smaller SIM card, the mini-SIM card. Mini-SIM cards have the same thickness as full-size cards, but their length and width are reduced to 25 mm × 15 mm.



A SIM card contains its unique serial number (Integrated Circuit Card ID), internationally unique number of the mobile user (IMSI), security authentication and ciphering information, temporary information related to the local network, a list of the services the user has access to and two passwords: a personal identification number (PIN) for ordinary use and a personal unblocking code (PUK) for PIN unlocking.





Security features include Authentication and encryption to protect data and prevent eavesdropping.



The SIM card performs the following valuable functions:

1. Identification of a subscriber

2. Authentication of a subscriber

3. Storage: To store phone numbers and SMS.

4. Applications: To provide basic information on demand and other applications for m-commerce, chatting, cell broadcast, phonebook backup, location based services etc.

References:

• http://www.mpf.org.in/pdf/technology/SIM_Card_Committee_Report.pdf

• http://en.wikipedia.org/wiki/Subscriber_Identity_Module