A SIM card or SIM (subscriber identity module) is a type of integrated circuit, often in the form of a smart card. They are intended to securely store an international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephone devices (such as mobile phones, tablets, and laptops). SIMs are also able to run apps and to store arbitrary information like address book contact information, and may be protected using a PIN code to prevent unauthorized use. These SIM cards are always used on GSM phones; for CDMA phones, they are needed only for LTE-capable handsets. SIM cards are also used in various satellite phones, smart watches, computers, or cameras. The first SIM cards were the size of credit and bank cards; sizes were reduced several times over the years, usually keeping electrical contacts the same, to fit smaller-sized devices. SIMs are transferable between different mobile devices by removing the card itself.
Technically, the actual physical card is known as a universal integrated circuit card (UICC); this smart card is usually made of PVC with embedded contacts and semiconductors, with the SIM as its primary component. In practice the term "SIM card" is still used to refer to the entire unit and not simply the IC. A SIM contains a unique serial number, integrated circuit card identification (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 four passwords: a personal identification number (PIN) for ordinary use, and a personal unblocking key (PUK) for PIN unlocking as well as a second pair (called PIN2 and PUK2 respectively) which are used for managing fixed dialing number and some other functionality. In Europe, the serial SIM number (SSN) is also sometimes accompanied by an international article number (IAN) or a European article number (EAN) required when registering online for the subscription of a prepaid card.As of 2020, eSIM is superseding physical SIM cards in some domains, including cellular telephony. eSIM uses a software-based SIM embedded into an irremovable eUICC.
History and procurement The SIM card is a type of smart card, the basis for which is the silicon integrated circuit (IC) chip. The idea of incorporating a silicon IC chip onto a plastic card originates from the late 1960s. Smart cards have since used MOS integrated circuit chips, along with MOS memory technologies such as flash memory and EEPROM (electrically EPROM). The SIM was initially specified by the ETSI in the specification TS 11.11. This describes the physical and logical behaviour of the SIM. With the development of the Universal Mobile Telecommunications System (UMTS), the specification work was partially transferred to 3GPP. 3GPP is now responsible for the further development of applications like SIM (TS 51.011) and USIM (TS 31.102) and ETSI for the further development of the physical card UICC. The first SIM card was manufactured in 1991 by Munich smart-card maker Giesecke+Devrient, who sold the first 300 SIM cards to the Finnish wireless network operator Radiolinja, who launched the world's first commercial 2G GSM cell network that year. Today, SIM cards are considered ubiquitous, allowing over 8 billion devices to connect to cellular networks around the world daily. 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 was predicted by Ericsson to drive the growth of the addressable market for SIM cards to over 20 billion 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.
Design
There are three operating voltages for SIM cards: 5 V, 3 V and 1.8 V (ISO/IEC 7816-3 classes A, B and C, respectively). The operating voltage of the majority of SIM cards launched before 1998 was 5 V. SIM cards produced subsequently are compatible with 3 V and 5 V. Modern cards support 5 V, 3 V and 1.8 V.
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 (the toolkit for smart cards), ETSI TS 102 241 (API), ETSI TS 102 588 (application invocation), and ETSI TS 131 111 (toolkit for more SIM-likes). SIM toolkit applications were initially written in native code using proprietary APIs. To provide interoperability of the applications, ETSI chose Java Card. A multi-company collaboration called GlobalPlatform defines some extensions on the cards, with additional APIs and features like more cryptographic security and RFID contactless use added.
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