subscriber identity module

from The Free On-line Dictionary of Computing (8 July 2008)

Subscriber Identity Module
SIM

   <telecommunications, wireless communications> (SIM or "SIM
   card") A component, usually in the form of a miniature
   smart-card, that is theoretically tamper-proof and is used to
   associate a mobile subscriber with a mobile network
   subscription. The SIM holds the subscriber's unique {MSISDN}
   along with secret information such as a private encryption key
   and encryption/digital signature algorithms.  Most SIMs also
   contain non-volatile storage for network and device
   management, contact lists, text messages sent and received,
   logos and in some cases even small Java programs.

   (2007-01-06)