SIM-card - a device that representssubscriber identification module. This is an integrated circuit designed to safely store the International Mobile Subscriber Identity Number (IMSI) and the associated key, which are used to identify and authenticate subscribers on mobile telephony devices (eg, 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. Also they can be used in satellite phones.
The SIM card is part of the universalan integrated circuit (UICC), which is usually made of PVC with built-in contacts and semiconductors. A sim card, based on digital technology, can transfer data between different mobile devices.
The SIM card contains:
- unique serial number (ICCID);
- international mobile communication 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 the PIN.
History and market entry
Initially, the SIM format was definedEuropean Telecommunications Standards Institute 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 was partially transferred to 3GPP.
The first SIM card was developed in 1991 by the manufacturer of Munich smart cards Giesecke & Devrient, which sold the first 300 copies to the Finnish operator of the Radiolinja wireless network.
In many contractual agreements, "with payment foryou need to periodically use the prepay to avoid expiration of your account. This period depends on 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.
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 "simoks", launched prior to 1998, was 5 V. The subsequently created cards are compatible with 3 V and 5 V. The current instances support a voltage of 5 V, 3 V and 1, 8 V.
SIM-cards store information about the network,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 emergency number for the operator.
A sim card, the device of which 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 (SDN), Advanceofcharge and VAS.
SIM-cards can be delivered in different volumesdata from 8 to at least 256 KB. All of them allow to store a maximum of 250 contacts, but if there is room for 33 mobile network codes (MNCs) or "network identifiers" in the 32-KB version, a version on 64 KB holds for 80 MNCs. 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 card canuse this to connect the phone to the preferred network to use the best commercial agreement for the source network company. This does not mean that the phone containing this SIM can connect to a maximum of 33 or 80 networks, which means only that the SIM-card issuer can specify only up to this number of preferred networks. If the SIM is outside of these preferred networks, it will use the first or best available of them.
Each SIM card is identified on theinternational level by ICID. ICCIDs are stored on SIM cards, as well as engraved or printed on the case during the personalization process.
ICCID is determined by the recommendation of ITU-T E.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 Moon algorithm. However, GSM Phase 1 defined the ICCID as 10 octets (20 digits) with a specific operator structure.
International Mobile Subscriber Identity (IMSI)
SIM cards are identified on individual networksoperators using a unique international mobile subscriber identity (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). The three-digit MNC codes are permitted by E.212, but are mainly used in the United States and Canada.
The following figures representmobile subscriber identification number (MSIN). Usually this is 10 digits, but the value will be smaller in the case of a three-digit MNC or if the national rules indicate that the total length of the IMSI should 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 circuit is standard and factory, the difference is observed only in the recorded information.
Authentication Key (Ki)
Kni is the 128-bit value used forSIM-card 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 the Authentication Center, or AuC) in the carrier's network.
How does the SIM card work in the light of the above? It is designed in such a way that KI can not be received with the help of a smart card interface. Instead, the SIM card provides the "Launch GSM algorithm" function, which allows the phone to transmit data to the SIM, which must be signed with Ki. This in theory makes the use of a SIM card mandatory, if Ki can not be extracted from the SIM card or the operator wants to open this parameter. In practice, the GSM cryptographic algorithm for calculating SRES_2 (see step 4 below) from Ki has certain vulnerabilities that can allow the extraction of this value from the SIM and the creation of a duplicate SIM card.
When mobile equipment starts, itreceives 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 the PIN to the SIM card before it opens this information.
Location Area Identification
SIM stores information about the network status thatis received from the location-area identifier (LAI). Network operators are divided into areas of location, each of which has a unique LAI number. When the device changes location, it stores 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 retrieve the data from the SIM and search for the previous LAI. On this feature, there are some bugging devices with a SIM card.
SMS messages and contacts
Most SIM-cards will be stored by defaulta number of SMS messages and phone book contacts. Contacts are stored in simple pairs "name and number": records containing several phone numbers and additional phone 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 attempts to copy such records to a SIM card, the phone's software splits them into several records, discarding any information that is not a phone 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 items.
SIM card: device and formats
With years of development SIM-cards have become smaller, and theirfunctionality does not depend on the format. Behind the full-sized "simka" came mini-SIM, micro-SIM and nano-SIM. Today they are even built into devices.
Full-size SIM card
A full-sized SIM card (or 1FF, 1-stform 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 built-in a full-sized card, from which they can be pushed out.
The mini-SIM (or 2FF) card has the samecontact device as a full-size SIM card, and is usually supplied in a full-size adapter attached to it by connecting elements. This scheme allows you to use it in a device that requires a full-size card, and in a device that requires a mini-SIM card (after breaking the connectors). Since the full-sized SIM is no longer used, some vendors call this form factor a standard or regular SIM card.
The micro-SIM (or 3FF) card has a similar thickness and location of the contacts, but it is distinguished by a reduced length and width.
The micro-SIM format was presented by the Europeanthe Telecommunications Standards Institute (ETSI) for installation in devices too small for a mini SIM card. The form factor was mentioned in the working group 3GPP SMG9 UMTS, which is the body setting the standards for GSM SIM cards, in December 1998, and was subsequently agreed at the end of 2003.
The micro-SIM was developed for the reversecompatibility. The main problem was the chip contact area. Saving the same contact area allows the micro-SIM to be compatible with previous, larger SIM card readers by using 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 contacts led to numerous tutorials and YouTube videos with detailed instructions on how to trim a 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 does not become completely useless.
The nano-SIM (or 4FF) card was introduced 11October 2012, when mobile service providers in different countries began to deliver it for phones that support this format. Nano-SIM measures 12.3 × 8.8 × 0.67 mm and reduces the previous format to the contact area, while preserving the existing functions. A small rim of the 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 SIM cards 2FF or 3FF, and for this are made thinner, but many phone companies do not recommend it.
IPhone 5, released in September 2012, was the first device to use activated sim cards nano, followed by other phones.
The upcoming new generation of sim cards is callede-SIM or eSIM (embeddedSIM), which is an unchangeable embedded chip in the SON-8 package - soldering directly on the circuit board. It will have the capabilities of M2M and remote access to the SIM card.