04 - SIM/UICC Flashcards
Explain IMSI?
International Mobile Subscriber Identity. This is a unique identifier that defines a subscriber in the wireless world, including the country and mobile network to which the subscriber belongs. It has the format MCC-MNC-MSIN. MCC = Mobile Country Code (e.g. 310 for USA); MNC = Mobile Network Code (e.g. 410 for AT&T), MSIN = sequential serial number. All signaling and messaging in GSM and UMTS networks uses the IMSI as the primary identifier of a subscriber.
The IMSI is one of the pieces of information stored on a SIM card.
Explain ICCID?
Integrated Circuit Card ID. This is the identifier of the actual SIM card itself - i.e. an identifier for the SIM chip. It is possible to change the information contained on a SIM (including the IMSI), but the identify of the SIM itself remains the same.
Explain IMEI?
IMEI is short for International Mobile Equipment Identity and is a unique number given to every single mobile phone, typically found behind the battery.
IMEI numbers of cellular phones connected to a GSM network are stored in a database (EIR - Equipment Identity Register) containing all valid mobile phone equipment.
When a phone is reported stolen or is not type approved, the number is marked invalid.
Explain MSISDN?
Mobile Station ISDN number. This is the full phone number of a subscriber, including the national country code (e.g. 1 for US, 44 for UK, etc.). The purpose of the MSISDN is simply to allow a device to be called. A subscriber can have multiple MSISDNs (e.g. one phone number for business, one for personal calls, one for fax, etc.), but generally only one IMSI. The MSISDN does not need to be stored on the SIM card. In cases where it is stored on the SIM, the main reason is so that the user can use check to see what their own MSISDN is (in case they forget). The MSISDN is never signaled to of from the device.
What is SIM?
Subscriber Identity Module is the ICC defined for 2G GSM Networks including the physical card and logical application.
What is UICC?
Universal Integrated Circuit Card is the physical card as defined for the UMTS and LTE networks.
ICCs are designed to identify and authenticate the user, setup encryption on the network and provide secure storage for user and network data. There are three types of cards.
What types of SIM cards are present?
- 1FF (Full-size / Credit Card)
- 2FF (Mini-SIM)
- 3FF (Micro-SIM)
- 4FF (Nano-SIM)
- Machine-2-Machine Form Factor (M2MFF) = eSIM / eUICC; are used for Kindle eReaders or Car Systems
What are the compontents of a SIM card?
SIM cards are mini-computers with min. Come in various capacities (8 KB - 256 KB). The SIM card contains a microcomputer as well as a certain amount of memory to process commands (Random Access Memory or RAM), and to store user files (Electronically Erasable Programmable Read Only Memory or EEPROM). The SIM also contains an amount of Read Only Memory (ROM) which stores the cards operating system. When the SIM card is activated the microcomputer loads the operating system from ROM into the RAM of the card and processes commands as requested by the mobile equipment (ME) or card access device (CAD). It consists of:
- Microprocessor
- Data Store (E Prom)
- Working Memory (RAM)
- Operating Software (ROM)
Explain the components of the SIM File Structure?
- Master File (MF - 0x3F00)
Mandatory root file containing access conditions and Dedicated and Elementary Files. The Master File or MF is the root of the file system. It is analogous to the root directory or “/” in the Linux file system; there is only one MF. An MF may contain one Dedicated File (DF) or many DFs and it may or may not contain one or many Elementary Files (EF).
- Dedicated File (DF - 0x7F00 / 0x5F00)
Underneath the MF in structure and can contain access conditions and DF and EF. The term Dedicated File is perhaps a bit confusing since the Dedicated File is more akin to a container or a sub directory rather than an actual file in the traditional sense. A dedicated file can also be identified by a two byte identifier. This identifier is assigned by the DF or the MF that contains it.Two Dedicated Files of interest are the DFGSM and the DFTELECOM. First level DF have a 2 byte file identifier of 0x7F00. Second level lDF have 0x5F00.
- Elementary File (EF - 0x2F00 / 0x6F00 / 0x4F00)
Sits usually underneath a DF in structure and contains access conditions and defined formatted data but there are exceptions.
Elementary Files (EF) sit below the Dedicated Files in the file system hierarchy (with the exception of the aforementioned EFICCID). These are the files that contain the actual data. An analogy to familiar computer file system terminology would be to say that the EF represents the leaf node of the file system.
The EF file under the MF can be identified by 0x2F00. The EF under a first level DF can be identified by 0x6F00. A EF under a second level DF can be identified with 0x4F00.
What is EFICCID?
It should be noted that there is one EF directly beneath the MF in the hierarchy. This EF identified by the marker EFICCID in the graphic above is the Integrated Circuit Card Identity (EF ICCID). This EF contains the unique serial number of each individual SIM card.
What is DFTELECOM?
The DFTELECOM contains more common telecom service features and can be used for other telecom applications in multipurpose SIMs. The phonebook EF which falls under this directory is an example of a more general telecom application. The DFTELECOM file can be identified by the 2 byte identifier of 0x7F10.
What is DFGSM?
The DFGSM contains applications for the GSM900 and GSM1800 MHz respectively. This directory contains EFs that are exclusive to GSM networks. The DFGSM file can be identified by the 2 byte identifier of 7F20.
Name the five File Access Control Levels of Elementary Files?
- Always
- Card Holder Verification 1 (CHV1)
- Card Holder Verification 2 (CHV2)
- Administrative
- Never
What are the four Elementary File Types?
- Transparent
- Linear Fixed
- Linear Variable
- Cyclical
Name data that can be retrieved from a SIM/UICC card?
-
Static data
ICCID, IMSI, Language preference, Authentication Key (Ki), Ciphering Key (Kc), Allowed / Forbidden PLMN’s, UCHV1/2 (PUK1/2) -
Dynamic data
TMSI, PTMSI, Location Area Code, CHV1/2 (PIN1/2) -
Phonebook / Contacts
SIM stores individual user record e.g. Name and Number. USIM stores multiple fields e.g. Name, Number and Email -
SMS messages
Capacity will vary Including deleted if not overwritten. -
Phone number
MSISDN
