Сим-карта – устройство, представляющее собой subscriber identity module. It is an integrated circuit designed to securely store an international mobile subscriber identification number (IMSI) and its associated key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). In addition, you can store contact information on many SIM-cards.
SIM cards are always used on GSM phones, for CDMA devices they are only needed for new LTE-compatible devices. They can also be used in satellite phones.
The SIM card is part of the universal function.integrated circuit (UICC), which is usually made of PVC with integrated contacts and semiconductors. A SIM card based on digital technology can transfer data between different mobile devices.
SIM card contains:
- unique serial number (ICCID);
- International Mobile Identity Identifier (IMSI);
- authentication and encryption;
- temporary information about the local network;
- list of services to which the user has access;
- The phone's SIM card device also has two passwords: a personal identification number (PIN) for normal use and a personal unlock code (PUK) for unlocking a PIN code.
History and market entry
Initially, the SIM format was determinedEuropean Institute of Telecommunications Standards in the specification with the number TS 11.11, describing the physical and logical properties of the SIM card. With the development of UMTS, the specification work has been partially transferred to 3GPP.
The first SIM card was developed in 1991 by Munich smart card maker Giesecke & Devrient, which sold the first 300 copies to the Finnish wireless network operator Radiolinja.
Inactivation
In many contractual agreementsgo "you need to periodically use the prepayment to avoid the expiration of the account. This period depends on the network operators, but usually a period of three months is defined. This is sometimes due to the fact that the SIM card becomes inactive on the network.
check in
Most countries and operators require identification to activate the service, but there are some exceptions, such as Hong Kong SAR.
How is the phone SIM card?
There are three operating voltages for SIM cards:5 V, 3 V and 1.8 V. The operating voltage of most of the sims running before 1998 was 5 V. The cards created afterwards are compatible with 3 V and 5 V. Modern specimens support 5 V, 3 V, and 1, 8 V.
Data
На SIM-картах хранится информация о сети, used to authenticate and identify subscribers in the network. The most important of these are ICCID, IMSI, authentication key (Ki), local area identifier (LAI), and the emergency number of the operator.
Sim card, whose device is based on diagrams,also stores other operator-specific data, such as the short message service center number (SMS ServiceServiceName), service provider name (SPN), service number numbers (SDN), Advanceofcharge parameters, and value added applications (VAS).
SIM cards can be supplied in various quantities.data from 8 to at least 256 KB. All of them allow you to store a maximum of 250 contacts, but, if in the 32 KB version there is space for 33 mobile network codes (MNC) or “network identifiers”, a 64 KB version is available for 80 MNC. This indicator is used by network operators to store information about preferred networks and is mainly used when the SIM is not in its home network, but in roaming. What does such a SIM card device mean?
The operator, who released the "SIM" canuse this to connect your phone to your preferred network in order to use the best commercial agreement for the original network company. This does not mean that a phone containing this SIM can connect to a maximum of 33 or 80 networks, which means that the issuer of a SIM card can only indicate up to this number of preferred networks. If Simka is outside of these preferred networks, it will use the first or best available one.
ICCID
Each SIM is identified byinternationally by integrated circuit identifier (ICCID). ICCIDs are stored on SIM cards, as well as engraved or printed on the case during the personalization process.
ICCID is determined by ITU-T E. Recommendation.118 as the Primary number. Its layout is based on ISO / IEC 7812. According to E.118, the number can be up to 22 digits, including one check digit calculated using the Luna algorithm. However, GSM Phase 1 defined the length of the ICCID as 10 octets (20 digits) with a specific operator structure.
International Mobile Subscriber Identity (IMSI)
SIM cards are identified on individual networks.operators using unique international mobile subscriber identification (IMSI). Mobile network operators connect to mobile phone calls and exchange their SIM cards on the market using their IMSI. Their format is as follows.
The first three digits represent the mobile country code (MCC).
The next two or three digits represent the mobile network code (MNC). Three-digit MNC codes are permitted by E.212, but are mainly used in the United States and Canada.
The following numbers representMobile Subscriber Identity Number (MSIN). This is usually 10 digits, but the value will be less in the case of a three-digit MNC or if national rules indicate that the total IMSI length must be less than 15 digits. All these figures differ from country to country, so there may be differences in how the SIM card is arranged. The scheme is standard and factory, the difference is observed only in the recorded information.
Authentication Key (Ki)
Kni is a 128-bit value used forSIM authentication in the GSM mobile network (for the USIM network, you still need Ki, but other parameters are required). Each SIM card stores a unique Ki, assigned to it by the operator during the personalization process. This parameter is also stored in a database (called an authentication center, or AuC) in a carrier network.
How does the SIM card with the foregoing?It is designed in such a way as to prevent the receipt of Ki using a smart card interface. Instead, the SIM card provides the “Run GSM-algorithm” function, which allows the phone to transfer data to a SIM card, which must be signed with Ki. This, in theory, makes the use of a SIM card mandatory if the Ki cannot be removed from the SIM card or the operator wants to disclose this parameter. In practice, the GSM cryptographic algorithm for calculating SRES_2 (see step 4 below) from Ki has certain vulnerabilities that may allow the extraction of this value from a sim card and the creation of a duplicate SIM card.
Authentication process
When mobile equipment starts up, itobtains the international mobile subscriber identity (IMSI) from the SIM card and sends it to the mobile operator requesting access and authentication. Mobile equipment can transfer a PIN code to a SIM card before it opens this information.
Location Area Identification
The SIM stores network status information, whichis taken from the location area identifier (LAI). Networks of operators are divided into location areas, each of which has a unique LAI number. When the device changes its location, it saves the new LAI on the SIM card and sends it back to the carrier network with the new location. If the device operates cyclically, it will extract data from the SIM card and search for the previous LAI. On this feature, some listening devices with a SIM card work.
SMS and contacts
Большинство SIM-карт будут по умолчанию хранить a number of SMS and phone book contacts. Contacts are stored in simple “name and number” pairs: records containing several telephone numbers and additional telephone numbers are usually not stored on it. Such conditions are provided by the SIM card device. Contacts can be kept very limited. For example, when a user tries to copy such entries to a SIM card, the telephone software breaks them up into several entries, discarding any information that is not a telephone number.
Number of saved contacts and messagesDepends on the SIM card. Early models will store only five messages and 20 contacts, while modern SIM cards can usually store more than 250 positions.
Sim card: device and formats
Over the years, the development of SIM-cards has become smaller, and theirThe functionality does not depend on the format. For a full-sized "SIM" followed by a mini-SIM, micro-SIM and nano-SIM. Today they are even embedded in devices.
Full size SIM card
Full-size SIM card (or 1FF, 1stform factor) became the first form factor. It has the size of a credit card (85.60 × 53.98 × 0.76 mm). Later, smaller “sims” were often sold as built-in full-size cards from which they could be pushed out.
Mini-sim
The mini-SIM card (or 2FF) has the samea contact device as a full-sized SIM card, and is usually supplied in a full-sized adapter attached to it by connecting elements. This scheme allows using it both in the device requiring a full-sized card and in the device requiring a mini-SIM card (after breaking the connecting elements). Since the full-size SIM is no longer used, some vendors call this form factor a standard or regular SIM card.
Micro-sim
The micro-SIM (or 3FF) card has a similar thickness and arrangement of contacts, but it is distinguished by a reduced length and width.
The micro-SIM format was introduced by the EuropeanTelecommunications Standards Institute (ETSI) for installation in devices that are too small for a mini SIM card. The form factor was mentioned in the 3GPP SMG9 UMTS working group, which is the standard setting body for GSM SIM cards, in December 1998, and subsequently agreed at the end of 2003.
Micro SIM was designed for reversecompatibility. The main problem was the contact area of the chip. Keeping the same contact area allows the micro-SIM to be compatible with previous, larger SIM card readers through the use of plastic cutouts. The device was also designed to work at the same speed (5 MHz) as the previous version. The same size and position of the contacts led to numerous tutorials and YouTube videos with detailed instructions on how to cut the mini-SIM card to the size of a micro-SIM. However, such actions at home sometimes lead to the fact that as a result the SIM card does not correspond to the device or it becomes completely unusable.
Nano-sim
Card nano-SIM (or 4FF) was presented 11October 2012, when mobile service providers in different countries began shipping it to phones that support this format. Nano-SIM has dimensions of 12.3 × 8.8 × 0.67 mm and reduces the previous format to the contact area, while maintaining the existing functions. A small bezel of insulating material remains around the contact area to avoid short circuits. Nano-SIM has a thickness of 0.67 mm compared to 0.76 mm of its predecessors. 4FF cards can be placed in adapters for use with devices designed for 2FF or 3FF SIM cards and made thinner for this, but many telephone companies do not recommend this.
The iPhone 5, released in September 2012, was the first device to use activated nano SIM cards, followed by other phones.
The upcoming new generation of SIM cards is callede-SIM or eSIM (embeddedSIM), which is an indispensable embedded chip in the SON-8 package - soldering directly onto the circuit board. It will have M2M and remote SIM access capabilities.
