Subscriber Identity Module ( SIM ), commonly referred to as " SIM card " or " telephone card", is a smart card mainly used to store user identification data, SMS data and phone numbers . Regarding SIM cards that are not entities , see eSIM card.
Nano SIM (4FF) not removed from the card
From left to right: full-size SIM (1FF), mini-SIM (2FF), micro-SIM (3FF) and nano-SIM (4FF)
SIM cards are mainly used in GSM networks and UMTS networks, but compatible modules can also be used in IDEN phones. Some people call the RUIM card and UIM card of CDMA2000 and cdmaOne also called SIM card. Although the two have similar functions and comply with all the same mechanical and electrical standards and some software standards, the upper layer applications are not necessarily compatible.
SIM is made up of CPU , ROM , RAM , EEPROM and I/O circuit . When the user uses the SIM, the mobile phone actually sends commands to the SIM card, and the SIM card should execute or reject it according to standard specifications; the SIM card is not a simple message storage.
The unique identifier of the SIM card is ICCID.
Physical Specifications
There are three operating voltages for SIM cards: 5 V, 3 V, and 1.8 V (ISO/IEC 7816-3 categories A, B, and C). Before 1998, most SIM cards worked at 5 V, and the SIM cards produced later supported 3 V and 1.8 V respectively. Currently used SIM supports three voltages of 5 V, 3 V and 1.8 V.
Current SIM cards allow loading programs to run while in use by the user. These programs communicate interactively with mobile phones or servers through the SIM toolbox, which is proposed by 3GPP in TS 11.13. The European Telecommunications Standards Institute (ETSI) has an identical but differently numbered specification. SIM card specifications are currently maintained by 3GPP and ETSI; the main specifications are: ETSI TS 102 223, ETSI TS 102 241, ETSI TS 102 588 and ETSI TS 131 111. SIM Toolbox programs are written using a private API . In order to ensure the interoperability of the program, ETSI proposed a Java Card solution. Other standards and specifications are maintained by Global Platform.
The physical specifications of the SIM comply with the regulations of the UICC, and there are four types:
- The earliest version was the same size as a standard credit card (85 x 54 x 0.78 mm), and the contacts conformed to ISO 7816 for ID-1 type IC cards.
- Due to the miniaturization of mobile phones, the SIM card is generally cut into a plug-in type of 25×15 mm (as shown in the figure, that is, UICC plug-in) for a long time. The SIM card of this size is also called "Mini SIM". It is usually embedded in an ID-1 card when it is sold, and it is removed along the prefabricated cutout before use.
- In 2003, the European Telecommunications Standards Institute (European Telecommunications Standards Institute) developed a "Micro SIM" card that was reduced from the Mini SIM to 15 x 12 mm. The Micro SIM card was first used in the iPad and iPhone 4 launched by Apple .
- In 2011, Apple proposed the "Nano SIM" card (8.8×12.3 mm) standard, which was adopted by the European Union as the 4FF standard after some competition in 2012. At that time, telecommunications companies in Europe stockpiled millions of "Nano SIM" cards to cope with iPhone 5 , iPhone 6 and iPhone 6 plus . Currently, more and more smartphone manufacturers adopt SIM cards of this size as standard.
- In response to the needs of wearable devices , vehicle-mounted devices, and the future Internet of Things, an " embedded SIM card " (eSIM, Embedded-SIM) has been developed after the 2010s. This SIM card is much smaller than a Nano SIM and is installed in the device. The user can change it by himself, but if the user needs to switch the mobile network operator , there is no need to change the physical SIM card, and only need to switch the settings in the device after application.
- In 2014, Apple launched Apple Sim, which was the first to be applied to its own tablet, but a few of its specifications are different from E-Sim. It was not until 2017 that its own watches began to use E-Sim.
Since the only difference between different SIM card standards is the size, and the contact standards are exactly the same, telecom operators will issue all-in-one SIM cards, and SIM cards of different sizes can be obtained by cutting along different cutting lines. There are also card cutters (to cut a large size SIM card into a small size) and card sleeves (to restore a small size SIM card to a large size) on the market.
| SIM card | introduction time | Introduce standard | Length (mm) | Width (mm) | Thickness (mm) |
|---|---|---|---|---|---|
| Full-size（FF） | year 1991 | ISO/IEC 7810:2003, ID-1 | 85.60 | 53.98 | 0.76 |
| Mini-SIM（2FF） | 1996 | ISO/IEC 7810:2003, ID-000 | 25.00 | 15.00 | 0.76 |
| Micro-SIM（3FF） | Year 2003 | ETSI TS 102 221 V9.0.0, Mini-UICC | 15.00 | 12.00 | 0.76 |
| Nano-SIM (4FF) | 2012 | ETSI TS 102 221 V11.0.0 | 12.30 | 8.80 | 0.67 |
| Embedded-SIM | 2017 | JEDEC Design Guide 4.8, SON-8 | 6.00 | 5.00 | <1.0 |
standard
SIM has been standardized by the GSM 11.11 standard, and users can easily move their accounts, short messages and directories between mobile phones. Similar in theory, users can also insert a SIM card from a new carrier on a phone provided by an old carrier to change accounts. But many carriers use SIM locks on the custom phones they sell to prevent losing customers to competitors. Whether SIM unlocking is legal depends on the laws of each country.
The PIN on the card protects what is stored on the card and how the card is used.
Vulnerabilities and Security
In 2013, the RT channel reported that German password cracking experts found that the SIM cards used by about 750 million users worldwide had vulnerabilities. Experts have notified the discovery to the International Telecommunication Union , which has also begun to notify relevant manufacturers to patch the vulnerability in time.
The SIM card only supports one-way authentication, not two-way authentication. That is, the network authenticates the legality of the mobile phone (SIM), and the lack of user authentication of the network leaves room for illegal activities such as " pseudo base stations ". The consequence is that criminals arbitrarily use other people's mobile phone numbers or arbitrary numbers Forcibly send spam text messages such as scams and promotions to users' mobile phones. This vulnerability can be resolved by upgrading the mobile phone card to a USIM card.
password protection
There are four types of passwords in the SIM card:
- PIN code (Personal Identification Number, also known as PIN1 code): This password can be set by the user, and can be used for power-on unlocking and other operations. If the wrong input is entered 3 times, the SIM card will be locked, and the PUK code needs to be used to unlock it.
- PUK code (Personal Unlock Key, also known as PUK1 code): This code is provided by the operator and can be used to unlock and reset the PIN code after entering the wrong PIN code 3 times. If the wrong code is entered more than 10 times, the SIM will not be able to continue to be used. At this time, you need to apply to the operator for a replacement card
- PIN2 code : mainly used for billing, etc. If you enter the wrong number 3 times, the SIM card will be locked, and you need to use the PUK2 code to unlock it
- PUK2 code : This password is provided by the operator, which can be used to unlock and reset the PIN2 code after entering the wrong PIN2 code 3 times. If the wrong input exceeds 10 times, the SIM will not be able to continue to be used. In this case, you need to apply for a new card from the operator.
The SIM card must work with the communication device
Countries around the world will have different frequencies (for example: 700MHz, 900MHz, 1800MHz, 1900MHz) and mobile communication technologies (for example: 2G , 3G , 3.9G , 4G ) in mobile communications. SIM cards are also divided into 2G , 3G , 3.9 G , 4G , if the two are not well matched with each other, the equipment will not be able to use the best specifications of the telecommunications system, or even completely unusable. For example, a 2G mobile phone with a 3G USIM card can only receive 2G signals, and the mobile data network will only have 2G specifications. For example, if a mobile phone that does not support 700MHz is used with a USIM card provided by a 700MHz carrier, it will be completely unusable. The SIM card should be paired with equipment that supports the SIM card format and carrier, so that the best specifications can be used. For example, when using a 4G mobile phone with a 4G USIM card, when using voice communication, switch from 4G VoLTE → 3.9G → 3G → 2G in order to optimize the call quality of the voice system.
related entries
References
- ^ Title: "Android Telephony Architecture Analysis and Implementation" Author: He LimingCurrent page: 230 pages
- ^ iPhone 5 and the nano-SIM stockpiles: a micro or major PITA? ( page archive backup , stored in) (in English)
- ^ . China Central Television News Network . [2013-07-24]. (Original content archived on 2013-07-29).
external link
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Related multimedia resources from Wikimedia Commons : SIM card |
- GSM11.11 ( page archive backup , stored in)
- GSM51.011 ( page archive backup , stored in)
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