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SIM Cards

Sim Authentication Forensics ICC-ID unique number identity

Integrated Circuit Card Identifier. An ICCID is a unique number assigned to each SIM card.

Sim-Subscriber Identity Module
The UICC (Universal Integrated Circuit Card) is a smart card which contains account information and memory that is used to enable GSM cellular telephones. One of the applications running on the smart card is the SIM, or Subscriber Identity Module. In common parlance the term "UICC" is not used an the phrase "SIM" is used to describe the smart card itself. Because the SIM is just one of several applications running on the smart card, a given card could, in theory, contain multiple SIMs. This would allow multiple phone numbers or accounts to be accessed by a single UICC. This is seldom seen, though there is at least one "12-in-1" SIM card being advertised at present.

ICC-ID is a unique identifier

Each SIM is internationally identified by its ICC-ID (Integrated Circuit Card ID). ICC-IDs are stored in the SIM card and can also be engraved or printed on the SIM card’s body during a process called personalization. The number is up to 18 digits long with an addition of a single “check digit” that is used for error detection. This single digit allows us to detect an input error of digits, mistyped digits or a permutation of two successive digits. This digit was calculated using the Luhn algorithm.

A typical SIM (19 digits) example 89 91 10 1200 00 320451 0, provide several details as follows:

  • The first two digits (89 in the example) refers to the Telecom Id.
  • The next two digits (91 in the example) refers to the country code (91-India).
  • The next two digits (10 in the example) refers to the network code.
  • The next four digits (1200 in the example) refers to the month and year of manufacturing.
  • The next two digits (00 in the example) refers to the switch configuration code.
  • The next six digits (320451 in the example) refers to the SIM number.
  • The last digit which is separated from the rest is called the “check digit”.

These digits can be further grouped for additional information:

  • The first 3 to 4 digits represents the Mobile Country Code (MCC) (Some cards only have 3 digits to represent the Telecom ID and country code.)
  • The next 2 digits represent the Mobile Network Code (MNC, AKA the mobile operator)
  • The next 12 digits is the number represent the Home Location Register
  • And mentioned above, the “check digit”

Location Area Identity

Operation networks for cell phone devices are divided into area locations called Location Areas. Each location is identified with its own unique identification number creating the LAI (Location Area Identity). A phone will store this number on its SIM card so it knows what location it’s in and to be able to receive service. If a phone were to change to a new Location Area, it stores the new LAI in the SIM card, adding to a list of all the previous LAIs it has been in. This way if a phone is powered down, when it boots back up, it can search its list of LAIs it has stored until it finds the one its in and can start to receive service again. This is much quicker than scanning the whole list of frequencies that a telephone can have access on. This is a real plus for forensic investigators because when a SIM card is reviewed, they can get a general idea of where the SIM card has been geographically. In turn this tells them where the phone has been and can then relate back to where the individual who owns the phone has been.

SIM Security

Information inside the UICC can be protected with a PIN and a PUK.

A PIN locks the SIM card until correct code is entered. Each phone network sets the PIN of SIM to a standard default number (this can be changed via handset). If PIN protection is enabled, the PIN will need to be entered each time phone is switched on. If the PIN is entered incorrectly 3 times in a row, the SIM card will be blocked requiring a PUK from the network/service provider.

A PUK is needed if the PIN is entered incorrectly 3 times and the SIM is blocked (phone is unable to make and receive calls/texts). The PUK can be received from the network provider, or possibly the GSM cell phone manual. Caution: if PUK is entered 10 times incorrectly, the SIM card is permanently disabled and must be exchanged.

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