A subscriber identity module or subscriber identification module ( SIM) is an integrated circuit that is intended to encryption store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as and ). It is also possible to store contact information on many SIM cards. SIM cards are always used on GSM phones; for CDMA phones, they are only needed for newer LTE-capable handsets. SIM cards can also be used in , computers, or cameras.
The SIM circuit is part of the function of a universal integrated circuit card (UICC) physical smart card, which is usually made of PVC with embedded contacts and . "SIM cards" are transferable between different mobile devices. The first UICC smart cards were the size of credit and bank cards; sizes were reduced several times over the years, usually keeping electrical contacts the same, so that a larger card could be cut down to a smaller size.
A SIM card contains its unique serial number (ICCID), international mobile subscriber identity (IMSI) number, 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: a personal identification number (PIN) for ordinary use, and a personal unblocking code (PUC) for PIN unlocking.
The first SIM card was developed in 1991 by Munich smart-card maker Giesecke & Devrient, who sold the first 300 SIM cards to the Finnish wireless network operator Radiolinja.
Today, SIM cards are ubiquitous, allowing over 7 billion devices to connect to cellular networks around the world. According to the International Card Manufacturers Association (ICMA), there were 5.4 billion SIM cards manufactured globally in 2016 creating over $6.5 billion in revenue for traditional SIM card vendors. The rise of cellular IoT and 5G networks is predicted to drive the growth of the addressable market for SIM card manufacturers to over 20 billion cellular devices by 2020. The introduction of Embedded SIM (eSIM) and Remote SIM Provisioning (RSP) from the GSMA may disrupt the traditional SIM card ecosystem with the entrance of new players specializing in "digital" SIM card provisioning and other value-added services for mobile network operators.
Modern SIM cards allow applications to load when the SIM is in use by the subscriber. These applications communicate with the handset or a server using SIM Application Toolkit, which was initially specified by 3GPP in TS 11.14. (There is an identical ETSI specification with different numbering.) ETSI and 3GPP maintain the SIM specifications. The main specifications are: ETSI TS 102 223, ETSI TS 102 241, ETSI TS 102 588, and ETSI TS 131 111. SIM toolkit applications were initially written in native code using proprietary APIs. To provide interoperability of the applications, ETSI chose Java Card.. Additional standard size and specifications of interest are maintained by GlobalPlatform.
SIM cards can come in various data capacities, from to at least . All can store a maximum of 250 contacts on the SIM, but while the has room for 33 Mobile Network Codes (MNCs) or network identifiers, the version has room for 80 MNCs. This is used by network operators to store data on preferred networks, mostly used when the SIM is not in its home network but is roaming. The network operator that issued the SIM card can use this to have a phone connect to a preferred network that is more economic for the provider instead of having to pay the network operator that the phone 'saw' first. This does not mean that a phone containing this SIM card can connect to a maximum of only 33 or 80 networks, but it means that the SIM card issuer can specify only up to that number of preferred networks. If a SIM is outside these preferred networks it uses the first or best available network.
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 digit "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 copies of SIM personalization datasets. Some datasets are without the ICCID checksum digit, others are with the digit.
As required by E.118, The ITU publishes a list of all current internationally assigned IIN codes in its Operational Bulletins. Links to current IIN list. the list issued on 15 November 2013 was current.
The SIM card is designed to prevent someone from getting the Ki by using the smart-card interface. Instead, the SIM card provides a function, Run GSM Algorithm, that the phone uses to pass data to the SIM card to be signed with the Ki. This, by design, makes using 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 SIM cloning.
SIM cards have been made smaller over the years; functionality is independent of format. Full-size SIM were followed by mini-SIM, micro-SIM, and nano-SIM. SIM cards are also made to embed in devices.
|+ SIM card sizes|
|Full-size (1FF)||1991||ISO/IEC 7810:2003, ID-1||85.60||53.98||0.76||3511.72|
|Mini-SIM (2FF)||1996||ISO/IEC 7810:2003, ID-000||25.00||15.00||0.76||285.00|
|Micro-SIM (3FF)||2003||ETSI TS 102 221 V9.0.0, Mini-UICC||15.00||12.00||0.76||136.80|
|Nano-SIM (4FF)||early 2012||ETSI TS 102 221 V11.0.0||12.30||8.80||0.67||72.52|
|JEDEC Design Guide 4.8, SON-8|
ETSI TS 103 383 V12.0.0
GSMA SGP.22 V1.0
The micro-SIM was introduced by the European Telecommunications Standards Institute (ETSI) along with SCP, 3GPP (UTRAN/GERAN), 3GPP2 (CDMA2000), ARIB, GSM Association (GSMA SCaG and GSMNA), GlobalPlatform, Liberty Alliance, and the Open Mobile Alliance (OMA) for the purpose of fitting into devices too small for a mini-SIM card.
The form factor was mentioned in the December 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 designed for backward compatibility. The major issue for backward compatibility was the contact area of the chip. Retaining the same contact area makes the micro-SIM compatible with the prior, 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 prior 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.
Micro-SIM cards were introduced by various mobile service providers for the launch of the original iPad, and later for smartphones, from April 2010. The iPhone 4 was the first smartphone to use a micro-SIM card in June 2010, followed by many others.
The iPhone 5, released in September 2012, was the first device to use a nano-SIM card, followed by other handsets.
The surface mount format provides the same electrical interface as the full size, 2FF and 3FF SIM cards, but is soldered to the circuit board as part of the manufacturing process. In M2M applications where there is no requirement to change the SIM card, this avoids the requirement for a connector, improving reliability and security. GSMA has been discussing the possibilities of a software based SIM card since 2010. While Motorola noted that eUICC is geared at industrial devices, Apple "disagreed that there is any statement forbidding the use of an embedded UICC in a consumer product." in 2012, The European Commission has selected the Embedded UICC format for its in-vehicle emergency call service known as eCall. All new car models in the EU must have one by 2018 to instantly connect the car to the emergency services in case of an accident. Russia has a similar plan with the ERA-GLONASS regional satellite positioning system.
In response, the International Telecommunication Union said that the development was "hugely significant" and that it would be contacting its members. UPDATE 1-UN warns on mobile cybersecurity bugs in bid to prevent attacks, Reuters, 2013-07-21, accessed 2013-07-21
In February 2015, it was reported by The Intercept that the NSA and GCHQ had stolen the encryption keys (Ki's) used by Gemalto (the manufacturer of 2 billion SIM cards annually), enabling these intelligence agencies to monitor voice and data communications without the knowledge or approval of cellular network providers or judicial oversight. Having finished its investigation, Gemalto claimed that it has “reasonable grounds” to believe that the NSA and GCHQ carried out an operation to hack its network in 2010 and 2011, but says the number of possibly stolen keys would not have been massive.
A virtual SIM is a mobile phone number provided by a mobile network operator that does not require a SIM card to connect phone calls to a user's mobile phone.
At the 2015 Mobile World Congress in Barcelona, Simless, Inc., a US-based startup unveiled world's first GSM phone without a SIM card slot. The reference phone was capable of downloading multiple virtual SIM cards over-the-air.
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.
Japan's 2G PDC system (which was shut down in 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. However, Japanese CDMA2000-based phones are locked to the R-UIM they are associated with and thus, the cards are not interchangeable with other Japanese CDMA2000 handsets (though they may be inserted into GSM/WCDMA handsets for roaming purposes outside Japan).
CDMA-based devices originally did not use a removable card, and the service for these phones bound to a unique identifier contained in the handset itself. This is most prevalent in operators in the Americas. The first publication of the TIA-820 standard (also known as 3GPP2 C.S0023) in 2000 defined the Removable User Identity Module (R-UIM). Card-based CDMA devices are most prevalent in Asia.
The equivalent of a SIM in UMTS is called the universal integrated circuit card (UICC), which runs a USIM application. The UICC is still colloquially called a SIM card.
On some networks, the mobile phone is SIM lock, meaning that the phone only works with SIM cards from the specific carrier. 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, 18 or 24 months). SIM cards that are issued by providers with an associated contract are called SIM-only deals. Common examples are the GSM networks in the United States, 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., India, Israel 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 carrier's traffic by different tariffs to different friends on different networks, or when traveling internationally.
In 2016, carriers started using the concept of automatic SIM reactivation whereby they let users reuse expired SIM cards instead of purchasing new ones when they wish to re-subscribe to that operator. This is particularly useful in countries where prepaid calls dominate and where competition drives high , as users had to return to a carrier shop to purchase a new SIM each time they wanted to churn back to an operator.
Within a SIM-only contract the mobile network provider supplies their customer with just one piece of hardware, a SIM card, which includes an agreed amount of network usage in exchange for a monthly payment. Network usage within a SIM-only contract can be measured in minutes, text, data or any combination of these. The duration of a SIM-only contract varies depending on the deal selected by the customer, but in the UK they are available over 1, 3, 6, and 12 month periods.
SIM-only contracts differ from mobile phone contracts in that they do not include any hardware other than a SIM card. In terms of network usage, SIM-only is typically more cost effective than other contracts because the provider does not charge more to offset the cost of a mobile device over the contract period. Short contract length is one of the key features of SIM-only made possible by the absence of a mobile device.
SIM-only is increasing in popularity very quickly. In 2010 pay monthly based mobile phone subscriptions grew from 41 percent to 49 percent of all UK mobile phone subscriptions. According to German research company GfK, 250,000 SIM-only mobile contracts were taken up in the UK during July 2012 alone, the highest figure since GfK began keeping records.
Increasing smartphone penetration combined with financial concerns are leading customers to save money by moving onto a SIM-only when their initial contract term is over.