Glossary:Subscriber Identity Module (SIM)
Subscriber Identity Module, abbreviated as SIM, is a smartcard that is necessary to make use of a mobile phone.
The SIM is the key used to identify and authenticate the mobile subscriber. On the SIM is also memory available for personalised data, such as a telephone book and messages.
The subscriber is identified with an IMSI, International Mobile Subscriber Identity, and a telephone number.
The SIM made a clear separation between a mobile phone and a subscriber possible. The subscriber can make use of any mobile phone under his own account if the SIM card is put in the phone. The use of a SIM can be guarded with a PIN code from 4 to 8 digits. If 4 times the wrong PIN code is typed, the SIM will be blocked. To unblock the SIM the PUK (PIN Unblocking Key) is needed. This is an 8 digits code that is known by the authorised user and given by the service provider.
The SIM card is essentially an internal integrated circuit card (ICC) providing diverse functionalities to establish an authenticated secure communication between the mobile device and the network.