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A subscriber identity module or subscriber identification module (SIM) is an integrated circuit that securely stores the service-subscriber key (IMSI) used to identify a subscriber on mobile telephony devices (such as mobile phones and computers).
A SIM is held on 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 (ICCID), 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 (PIN for usual use and PUK for unlocking).
The specification that standardized the micro-SIM form factor continues to evolve. Some features introduced recently include:
The number is composed of the following subparts:
; Issuer identification number (IIN): Maximum of seven digits:
With the GSM Phase 1 specification using 10 octets into which ICCID is stored as packed BCD, the data field has room for 20 digits with hexadecimal 'F' being used as filler when necessary.
In practice, this means that on GSM SIM cards there are 20-digit (19+1) and 19-digit (18+1) ICCIDs in use, depending upon the issuer. However, a single issuer always uses the same size for its ICCIDs.
To confuse matters more, SIM factories seem to have varying ways of delivering electronic copy of SIM personalization datasets. Some datasets are without the ICCID checksum digit, others are with the digit.
The SIM card is designed not to allow the Ki to be obtained using the smart-card interface. Instead, the SIM card provides a function, Run GSM Algorithm, that allows the phone to pass data to the SIM card to be signed with the Ki. This, by design, makes usage of the SIM card mandatory unless the Ki can be extracted from the SIM card, or the carrier is willing to reveal the Ki. In practice, the GSM cryptographic algorithm for computing SRES_2 (see step 4, below) from the Ki has certain vulnerabilities that can allow the extraction of the Ki from a SIM card and the making of a duplicate SIM card.
Authentication process: # When the Mobile Equipment starts up, it obtains the International Mobile Subscriber Identity (IMSI) from the SIM card, and passes this to the mobile operator requesting access and authentication. The Mobile Equipment may have to pass a PIN to the SIM card before the SIM card will reveal this information. # The operator network searches its database for the incoming IMSI and its associated Ki. # The operator network then generates a Random Number (RAND, which is a nonce) and signs it with the Ki associated with the IMSI (and stored on the SIM card), computing another number known as Signed Response 1 (SRES_1). # The operator network then sends the RAND to the Mobile Equipment, which passes it to the SIM card. The SIM card signs it with its Ki, producing SRES_2, which it gives to the Mobile Equipment along with encryption key Kc. The Mobile Equipment passes SRES_2 on to the operator network. # The operator network then compares its computed SRES_1 with the computed SRES_2 that the Mobile Equipment returned. If the two numbers match, the SIM is authenticated and the Mobile Equipment is granted access to the operator's network. Kc is used to encrypt all further communications between the Mobile Equipment and the network.
SIM cards are available in three standard sizes. The first is the size of a credit card (85.60 mm × 53.98 mm × 0.76 mm). The newer, most popular version has the same thickness, but has a length of 25 mm and a width of 15 mm, and has one of its corners truncated (chamfered) to prevent misinsertion. The newest incarnation, known as the micro-SIM or 3FF, has dimensions of 15 mm × 12 mm. Most cards of the two smaller sizes are supplied as a credit card size with the smaller standard card held in place by a few plastic links; it can easily be broken off to be used in a device that uses the smaller SIM.
The mini-SIM card has the same contact arrangement as the full-size SIM card and is normally supplied within a full-size card carrier, attached by a number of linking pieces. This arrangement (defined in ISO/IEC 7810 as ID-1/000) allows for such a card to be used in a device requiring a full-size card, or to be used in a device requiring a mini-SIM card after cleanly breaking the scorings manufactured in the outline of a mini-SIM card.
Even smaller device sizes have prompted the development of a yet smaller card size, the 3FF card or micro-SIM. Micro-SIM cards have the same thickness and contact arrangement again, but the length and width are further reduced to 15 mm × 12 mm. The specifications for the 3FF card or micro-SIM also include additional functionality beyond changing the physical card size.
The micro-SIM was developed by the European Telecommunications Standards Institute along with SCP, 3GPP (UTRAN/GERAN), 3GPP2 (CDMA2000), ARIB, GSMAssociaton (GSMA SCaG and GSMNA), GlobalPlatform, Liberty Alliance, and the Open Mobile Alliance (OMA) for the purpose of fitting into devices otherwise too small for a mini-SIM card.
The form factor was mentioned in the Dec 1998 3GPP SMG9 UMTS Working Party, which is the standards-setting body for GSM SIM cards, and the form factor was agreed upon in late 2003.
The micro-SIM was created with backwards compatibility in mind. The major issue with backwards compatibility was the contact area of the chip. Retaining the same contact area allows the micro-SIM to be compatible with the previous, larger SIM readers through the use of plastic cutout surrounds. The SIM was also designed to run at the same speed (5 MHz) as the previous version. The same size and positions of pins resulted in numerous "How-to" tutorials and YouTube video with detailed instructions how to cut a mini-SIM card to micro-SIM size with a sharp knife or scissors. These tutorials became very popular among first owners of iPad 3G after its release on April 30, 2010 and iPhone 4 on June 24, 2010.
The chairman of EP SCP, Dr. Klaus Vedder, said :"With this decision, we can see that ETSI has responded to a market need from ETSI customers, but additionally there is a strong desire not to invalidate, overnight, the existing interface, nor reduce the performance of the cards. EP SCP expect to finalise the technical realisation for the third form factor at the next SCP plenary meeting, scheduled for February 2004."
USIM (Universal Subscriber Identity Module) is an application for UMTS mobile telephony running on a UICC smart card which is inserted in a 3G mobile phone. There is a common misconception to call the UICC itself a USIM, but the USIM is merely a logical entity on the physical card. It stores user subscriber information, authentication information and provides storage space for text messages and phone book contacts. The phone book on a UICC has been greatly enhanced. For authentication purposes, the USIM stores a long-term pre-shared secret key, which is shared with the Authentication Center (AuC) in the network. The USIM also verifies a sequence number that must be within a range using a window mechanism to avoid replay attacks, and is in charge of generating the session keys to be used in the confidentiality and integrity algorithms of the KASUMI block cipher in UMTS. The equivalent of USIM on CDMA networks is CSIM.
The use of SIM cards is mandatory in GSM devices.
The satellite phone networks Iridium, Thuraya and Inmarsat's BGAN also use SIM cards. Sometimes these SIM cards work in regular GSM phones and also allow GSM customers to roam in satellite networks by using their own SIM card in a satellite phone.
IC-Card]]
Japan's 2G PDC system (which will be completely shut down by 2012; SoftBank Mobile has already shut down PDC from March 31, 2010) also specifies a SIM, but this has never been implemented commercially. The specification of the interface between the Mobile Equipment and the SIM is given in the RCR STD-27 annex 4. The Subscriber Identity Module Expert Group was a committee of specialists assembled by the European Telecommunications Standards Institute (ETSI) to draw up the specifications (GSM 11.11) for interfacing between smart cards and mobile telephones. In 1994, the name SIMEG was changed to SMG9.
Japan's current and next generation cellular systems are based on W-CDMA (UMTS) and CDMA2000 and all use SIM cards.
The equivalent of a SIM in UMTS is called the Universal Integrated Circuit Card (UICC), which runs a USIM application, while the Removable User Identity Module (R-UIM) is more popular in CDMA-based devices e.g. CDMA2000. The UICC is still colloquially called a SIM card.
On some networks, the mobile phone is locked to its carrier SIM card, meaning that only the specific carrier's SIM cards will work. This is more common in markets where mobile phones are heavily subsidised by the carriers, and the business model depends on the customer staying with the service provider for a minimum term (typically, 12 or 24 months). Common examples are the GSM networks in the USA, Canada, Australia, the UK and Poland. Many businesses offer the ability to remove the SIM lock from a phone, effectively making it possible to then use the phone on any network by inserting a different SIM card. Mostly, GSM and 3G mobile handsets can easily be unlocked and used on any suitable network with any SIM card.
In countries where the phones are not subsidised e.g. Italy, India and Belgium, all phones are unlocked. Where the phone is not locked to its SIM card, the users can easily switch networks by simply replacing the SIM card of one network with that of another while using only one phone. This is typical, for example, among users who may want to optimise their telecoms traffic by different tariffs to different friends on different networks.
Category:Mobile phone standards Category:Cryptographic hardware Category:Smart cards Category:Computer access control
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