SIM cards - functions and features. A Brief Introduction to SIM Cards

Mobile communications have become our faithful companion. It's hard to imagine traveling by car, getting ready out of town, working, or even going to the store without a cell phone. The pipe becomes a lifesaver in any difficult situation. A person is accustomed to his small communicator, and the connection that has been established between the cellular device and its owner is much stronger than that offered to you by the operator. Try not taking your cell phone with you for a couple of days. Thoughts about missed meetings, possible troubles while driving, or meeting anxiety will overwhelm you. This is how the body will react to the absence of 100 grams of plastic and semiconductors. If the cell phone is so important to us, then why do we know so little about it? Our series of articles “Secrets of Communication” should change this. We will introduce you to many interesting moments from life cellular communications and give a basic idea of ​​the hardware.

Today we will talk about the SIM card. Most users do not pay any attention to this microcomputer. But without a shadow of embarrassment, we can say that the SIM card is the heart of your cellular device. The convenience and simplicity of this solution, on the one hand, bring it to the same level as the invention of the wheel. On the other hand, the SIM card has absorbed everything new from modern digital progress. The solution is not just a static device, but a serious evolving chip. The capabilities of which are far from being fully utilized.

Why SIM card?

The history of any device is closely connected with the question - “Why”? They say that if a child asks it at the age of 2, then he grows into a genius. If the cherished word is spoken at the age of five, then we have before us a simple individual. It becomes excruciatingly painful when you think about at what age we ask this question. So, by clearly answering why the SIM card was created, we will wash away the shame of the time delay of this issue.

Any cell phone must be uniquely identified by the operator's network. First of all, this must be done to withdraw money from him for the services provided. In addition, identification serves as the key to the provision of all services. When connected to the network, the handset receives a unique designation, which is entered into a special register. At first, the issue of assigning a code to each phone was resolved very simply. The operator used a unique Electronic Serial Number (ESN) - the serial number of the device. Most likely, this happened by analogy with the automobile industry. It is no secret that previously in many countries a license plate was assigned to a car at the factory and accompanied the car throughout its life (not to be confused with the body number or VIN number). This approach is completely justified, even despite the obvious problems that are associated with the necessary agreements on formats and common databases data. So, the first phones were online under their Electronic Serial Number (ESN). Problems appeared very quickly. More and more manufacturers of cell phones and equipment for mobile networks began to enter the market. It should be noted that they did not have warm relationships with each other, like any normal competitors in a dynamically developing market. Therefore, it has become almost impossible to agree on common Electronic Serial Number (ESN) formats. Of course, after some time this chaos would be brought into order. However, the thunder that struck from the users did not allow this scenario to develop. The fact is that in those days, visiting a cellular operator to register with it and other formal manipulations became a heavy duty for the subscriber. Cellular communications, which looked and presented as a sprout of freedom, appeared as a heavy burden. In a word, Electronic Serial Number (ESN) did not suit a certain audience at all. All efforts were thrown into searching for alternative routes. They were found. To be fair, I note that even now a number of networks in the world use Electronic Serial Number (ESN) to identify a subscriber, but there are no visible prospects in this direction and this approach is doomed to extinction. So, we dealt with the identified problem in a very interesting way. It was decided to separate the identification of the cell phone and the subscriber. Initially it looked extremely attractive. Over time, shortcomings appeared, which we will talk about later. So, the GSM standard imposed an obligation on cell phone manufacturers - each handset must have a 15-digit unique number IMEI (International Mobile Equipment Identifier). There are special services that monitor and distribute number ranges for development companies. If you are familiar with computers, then this is an analogue of the MAC address of a network card. So, the cellular handset is recognized by the operator using the IMEI code. But the subscriber is separated from the cell phone. A SIM card is used to identify it. This device becomes an integral companion to all your conversations (except for calls emergency services by number 112, which can be done even without a SIM card). Initially, the following requirements were put forward for this device:

• separate module;
• built-in memory and processor for executing commands;
• programming capability;
• finished goods

. All these conditions were met and one of the most popular microcomputers today hit the market.

Stages of SIM card development

Time stage	Evolution of the SIM card
	SIM card memory and supply voltage	SIM card functions
1991–1993	8 KB, 5.5 Volts	incoming and outgoing calls, call forwarding, call barring, call waiting, card blocking, PLMN network selection (roaming feature), SMS (reception only), speed dialing, sending and receiving fax messages, prohibiting work in networks without a roaming agreement - FPLMN.
1994-1997	8 KB; 5.5 and 3.3 Volts	Supports all functions of the previous window plus additional ones - PIN2 (data field protection), fixed dialing, SMS (added the ability to send), SMS status, auto-dial last number, menu language selection, message personalization, support for multiple numbers (voice, digital, fax) ), repeating the last number dialed, long numbers (more than 20 digits), displaying the service provider, Caller ID, anti-Caller ID, group call, creating a closed group of up to 10 subscribers, voice messages.
1997 to present	16 KB, 64 KB, 3.3 Volts; 1.8 Volts	It is in the formative stage. More than 50 new features have been added. Among them (the most interesting and promising) are SIM Application Toolkit, Enhanced Full Rate, as well as GSM and DECT interaction. Java support.

One simple pattern can be traced - SIM card becomes a more technologically advanced solution. The memory capacity grows along with the range of functions. What does the future hold for us? First of all, a jump in SIM card memory expansion is possible. Developers and engineers have repeatedly reported that they are ready to introduce a 1 MB SIM card to the market. However, this does not happen. What is the reason? New SIM cards cost more and someone will have to pay for them. No one will do this unless they see obvious benefits. Doubts come from the flash memory card market. They can become a universal repository of information. The cost of these solutions is significantly lower than SIM cards. In addition, the purchase of additional memory is a constitutional and democratic event, which means that when purchasing, the subscriber will not have to overpay for extra free space. And yet there is information that is not convenient to carry far from the SIM card, and the latter will still grow in digital volume. The second obvious step is to reduce the supply voltage. Work is underway here. These steps must be coordinated with cell phone manufacturers. Remember the GSM market 5 years ago, when new phones refused to work with old cards (or rather, the opposite - old SIM cards with new phones)? The inertia here is huge, but reducing the power increases the life of the cell phone, since the power spent on operating the SIM card becomes less.

SIM card under magnifying glass

So, it became clear to us that a SIM card is a subscriber identification module containing a microprocessor and memory in which various information can be stored. It meets all ISO 7816 specifications and operates according to the T=0 protocol ISO class A0h. This is a microcomputer based on an 8-bit processor. It is framed by three types of memory: ROM, RAM and EEPROM. Operators are very interested in the last component, which reaches 64 kb and can serve as a container for organizing service capabilities (SIM menu or SIM Service). Non-volatile EEPROM memory is programmed remotely (with the user's permission). Therefore, your mobile operator can add or remove new menu items to your phone via a message sent to you.

Now it has become clear how the operator creates new services on your phone. Everything is very simple. The situation is reminiscent of the operation of a regular computer. Remember that if the SIM card is removed from the handset, the information on it cannot be lost. On the other hand, it shouldn't surprise you that removing or changing the SIM card can change your phone's menu. Let's take a quick look at the memory structure of a SIM card. The root directory MF (Master File) contains subdirectories DF (Dedicated Files) and EF (Elementary File) files. Subdirectories, in turn, also contain files of the first and second levels. Each elementary file (EF) can belong to one of the following three families: transparent, linear, and circular. Elementary files contain a variety of service information. Such information can be the subscriber's IMSI code, a list of supported languages, a table of available services, etc. The file consists of a header and a body. The header describes in detail the structure of the file and the conditions for accessing it. The body contains the actual data.

• A transparent file consists of a certain number of bytes, available individually and in blocks, for which it is necessary to specify their relative address (offset) and length (length).
• A linear file consists of a sequence of records of a fixed length and should therefore be treated as sequential. The maximum size of such a file is 255 records per 255 bytes, not counting the extension.
• The loop file contains certain number fixed length records. Moreover, each new entry always takes the first position, while the last one is “overwritten”.

The microprocessor of the SIM card is controlled by commands, like any other chip of the same class. We know of 18 teams. Perhaps there are undocumented ones.

So, a SIM card appeared before us, like a small computer. The device has a microprocessor that is controlled by commands. Information is stored in memory. Her organization follows strict rules. Does your computer sometimes crash? The SIM card is no different from it...

SIM card protection and malfunctions

The owner of the SIM card is able to make calls, transfer information or use other services. Its correct identification becomes the key to spending money. And where hard coins appear, you should definitely expect unscrupulous people who will try to rob you. This is the nature of human relationships at the top of the evolutionary path. Manufacturers try to give the user maximum opportunities to maintain control over their item. In other words, locks, ciphers, codes and guards are our best friends in this world. The SIM card also has its own lock. The key to it is the Personal Identification Number - PIN code. The user receives it when purchasing a card. You can enable (almost) all functions of the SIM card only by dialing it correctly. In case of an error (the user is given three attempts), identification does not occur and the card is blocked. You can bring it back to life only after entering the Personal Unblocking Key - PUK code (ten entry attempts). The PIN and PUK code was originally planned to be set to 8 digits. However, to make life easier for subscribers, the PIN code has been shortened to 4 characters. PUK consists of 8 digits. Some users remove protection from the SIM card. This is done through the phone menu. After this, the device does not require the owner to enter a PIN code when turned on or other associated events. There are also PIN2 and PUK2 codes. They help reveal additional features SIM cards. For example, they initiate commands to bar incoming or outgoing calls. Removing this code is also possible and responsibility for this step lies with the subscriber. Most often, according to service statistics, failures in the operation of SIM cards occur after they are mechanically damaged. The culprit of our review is very fragile. Modern cell phones have hard grips for SIM cards. Users diligently break them in the stubs. Replacing a broken SIM card is easy, but restoring the contents is often impossible. The second most common problem is forgetting your PIN code. After entering it three times, the phone is blocked. A dozen unsuccessful attempts to enter PUK and the SIM card turns into trash. A prompt appears on your cell phone screen to visit your operator to replace your SIM card. The pleasure is almost always paid and requires a passport for your identification. You are given a new SIM card and new codes for it. Very rarely, users report that their cell phone stops accepting the SIM card. A message appears on the screen that clearly indicates this. You can take out the SIM card, clean its contacts (ethyl alcohol will help do this, but you should not equate cleaning delicate gold contacts with removing rust from an old sheet of iron) and reinstall it into the mobile device. If the situation does not change, then feel free to contact the operator. Your SIM card, like any computer, is subject to failure. The situation is not very pleasant. The operator will exchange the damaged device for a new one absolutely free of charge (demand it), but all the information on the SIM card will be hopelessly lost for you. Personal experience suggests that all requests to restore it have encountered a wall of misunderstanding and an unequivocal assurance that this is impossible to do and this is not stipulated in the contract.

Attackers and your SIM card

Is it possible to clone SIM cards? Theoretically, this process can be solved quite simply. The attacker must copy the service information from the SIM card (International Mobile Subscriber Identity (IMSI), its individual encryption key (Ki) and the cryptographic algorithm program (A3)) to a blank blank. Thus, an absolutely identical clone will appear on the network, which will be able to spend money on the same basis as the original. Is it possible for a complete clone to exist on the network? A number of operators answer with absolute confidence that such a possibility is completely excluded. A subscriber with a double (one-time presence on the network) will be instantly disconnected until all circumstances are clarified. Indeed, operators maintain the user register very strictly. Catching multiplied subscribers is not difficult. However, recently an experiment was conducted (we are deliberately keeping silent about the operators and countries of this experiment) on cloning SIM cards. It turns out that some operators do not have protection for this case. Blind confidence in the impossibility of cloning GSM network users can play into the hands of attackers. How to clone a SIM card? Theoretically, it is enough to intercept big package data on air. After that, extract the necessary data from there. In reality this method doesn't work. There is no way to force the phone to broadcast as much as needed. Therefore, you should only be wary of direct theft of your SIM card. Devices for reading and writing them can be bought in any large city without any licenses. Making a take requires a minimum of knowledge and only a few minutes. Therefore, beware of giving your SIM card into the wrong hands. Otherwise, information about your personal account may bring you a number of unpleasant surprises.

Instead of a conclusion

Let's summarize: a SIM card is an ordinary microcomputer. It is the heart of your cell phone and, unfortunately, this device is not infallible - it can break. In our review, we focused on talking about a SIM card for GSM networks. Devices that are used in satellite phones or networks of other operators, on basic level almost identical. They may differ in memory size, command set, service information, and so on. In our next article we will tell you how to build GSM communication in modern networks.

All questions, comments and suggestions can and should be asked at

Today, every mobile owner has at least one SIM card. We are so used to these small pieces of plastic with gold-plated contacts that we don’t even think about what a miracle of technology we are using.

Drawing on the theme “Secrets of SIM cards”

How SIM cards appeared

SIM stands for Subscriber Identification Module or Subscriber Identification Module. As the name suggests, the SIM card serves to identify the subscriber in the cellular network.

SIM card

At first, user identification on the network was carried out based only on the factory number of a cell phone -. When there were few subscribers and equipment manufacturers, this approach was justified. As a result, the equipment, that is, the cell phone and the subscriber, were identified with a single code. Among other things, this approach created a complete dependence of, say, the service package and phone number on the device. That is, having changed your cell phone, you had to go to the operator’s office so that the serial numbers of your phone were entered into the database. If your mobile phone broke down, it took some time before you could use communication services again.

It would be much more convenient to have subscriber identification independent of the phone. This idea was guided by the developers of the GSM standard, who proposed separating the identification of subscribers and equipment. The Finnish company Radiolinija was the first to apply this idea in 1991.

The proposed identification scheme is still in effect today. In particular, as we have already said, a SIM card is used to identify a subscriber in GSM cellular networks (as well as in many others). For completeness, we note that modern cell phones are identified by the system using a 15-digit number - International Mobile Equipment Identifier).

Having talked about the history of SIM cards, let's try to take a closer look at these interesting devices.

What is a SIM card: purpose and development

In short, a SIM card is a computer. The SIM card contains a microprocessor, buses for input and output of information, a set of types typical for computers ROM memory(permanent), RAM (operational), EEPROM (rewritable). The card stores various data, some of which it handles with extreme care in order to ensure the safety of the subscriber.

In particular, the following information is stored on the card:

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Posted by: bourbon
Hello!
But still, tell me how to break it so that it looks almost the same as it was before the break

Posted by: Smart anonymous
Listen to the last comment talking about PIN and PACK codes. But think about it, the more protection, the worse it is for you. If your phone is locked, anyone can open it, but if it’s not locked, someone might call you.

Posted by: Andrey
I have a question: is it possible to find my SIM card, which is currently working, but I don’t know where the phone is located?

Posted by: evgen
please tell me how I can still break COMP128v2, otherwise my new generation SIM cards cannot be copied, maybe someone knows????

Posted by: sexmachine
HERE USE ID 9503140707

Posted by: LOH
do not store imsi and kai on your computer

There are two broad categories of ICCs. Memory cards contain only non-volatile memory storage components, and perhaps dedicated security logic. Microprocessor cards contain volatile memory and microprocessor components. A smart card, chip card, or integrated circuit card (ICC) is any pocket-sized card with embedded integrated circuits. Smart cards can provide identification, authentication, data storage, strong security authentication for single sign-on (SSO) and application processing. Physical, electrical and other characteristics of Smart cards are described by the ISO/IEC 7810 and ISO/IEC 7816 series of standards. Smart Card (SIM Card) pinout Pin Name Description C1 VCC +5 VDC power supply input (optional use by the card) C2 RESET Reset signal, used to reset the card's communications.

Sim world roaming-free sim cards

Diagram of connecting a SIM chip to a GSM module Due to the identity of SIM chips and SIM cards, it is possible to connect a SIM chip in combination with a SIM card to one GSM module. At the same time, the device developer must ensure proper multiplexing between identification modules. If the developer hardly has to edit the electrical circuit, then the design of the printed circuit board will change significantly - a lot of space will be freed up on it.
The SIM chip is made in the VQFN-8 form factor and occupies only 30 mm2 on the printed circuit board (Fig. 4). The pinout of the microcircuit is standard, it is shown in Fig. 5. Fig. 4. dimensions SIM chip VQFN-8 Fig. 5. SIM chip pinout Fast start Since SIM chips can now be classified as electronic components, it has become possible to purchase them from official partner cellular operator.

Pinout of smart card (sim card) interface

GSM devices in the operator’s cellular GSM/UMTS network to access services voice communication, SMS and digital data transmission via GPRS or CSD technologies. Historically, to identify a GSM device on a network, plastic-based SIM cards the size of a credit card (86x54 mm) were initially used, which had to be manually inserted into a mobile phone. In the process of popularizing cellular communications and with the advent of increasingly compact mobile phones, the SIM card only decreased in size (25x15 mm), still remaining plastic (Fig.

2). Rice. 1. Appearance of the SIM chip (5×6 mm) Fig. 2. Appearance of the SIM card To this day, the SIM card is a separate device and is distributed by cellular operators as a service that is aimed primarily at the mass, household sales market.

Phone SIM card: device

Attention

This process SIM cards (Subscriber Identification Module) are also used in all GSM devices. Conventional SIM cards have recently become available in a new form factor - in the form of microcircuits in a miniature VQFN-8 package. Such SIM cards are more correctly called SIM chips. Emergence of SIM chips on the market electronic components on free sale has opened up new opportunities for the industry of GSM devices, such as transport monitoring and security systems, telecommunications and trade and cash equipment, medical devices and telemetry complexes.

SIM chip - selection M2M SIM chips (Fig. 1) comply with the ETSI TS 102.671 standard and are designed for mounting directly on a printed circuit board using the soldering method. Functionally, the SIM chip is no different from a regular SIM card (Fig.

Sim cards. problems and solutions

Then the blank is clad with a film on the bottom side and this film covers the cavity of the adapter, preventing the card from falling through. Problem #2. The adapter clings to the contacts. This design has very sharp and wrinkle-resistant corners in the area of ​​​​contact with the connector contacts. The connector's diligence in ensuring reliable contact can be easily seen on used "soft" SIM cards of older types.

Info

And the adapter clings to the contacts very confidently and aggressively. Usually it is still possible to insert the unit into the connector, although with dangerously excessive force (it is pushed in “with the grain”), but when pulled out (“against the grain”) both parts “follow the principle”, and the procedure is only possible by tearing out one or two contacts connector. The adapter diagram is shown in the figure. The most dangerous thing is the internal “rib” indicated in the figure on the narrow crossbar of the adapter - it is this that rips out the connector contacts.

SIM card

Russian mobile operators for their subscribers ( legal entities) allow electronic document flow to simplify and speed up the process of connecting newly purchased devices with SIM chips. Integrating a SIM chip into a device The developer of a GSM device will not need much time to figure out how to connect the SIM chip to the GSM module. The chip, like the SIM card, has contacts VCC, I/O, RST, CLK and GND, and its connection diagram is almost no different from the SIM card connection diagram (Fig.

3), with one exception: there is no need for a protective diode in the case of SIM chips, since the possibility of damage to the lines by static electricity is eliminated. Protection diodes are recommended for SIM card devices where the user could touch the holder's electrical contacts and "discharge" the device. Rice. 3.

Communication secrets: part 1 – opening the SIM card

SIM card is a device that is a subscriber identification module. This is an integrated circuit designed for safe storage International Mobile Subscriber Identity (IMSI) numbers and associated key, which are used to identify and authenticate subscribers to 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 required 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 built-in contacts and semiconductors.

Simcard special connector at the card card pin Description 1 Vcc 2 Reset 3 CLK 4 GND 5 Vpp 6 I/O This information should be correct, but errors are possible. You can help! You can confirm the correctness of the document (only if you are really sure), or report an error in the document (the error can be described below in the link). Your opinion will be taken into account when calculating the status of the document.
Pinouts.ru Pinouts of memory chips Pinout of a Sim card using a 6 pin connector Simcard special Document status: not confirmed mark as erroneous! mark as correct 0 review(s) Click on one of the links to change the status of the document.

SIM card pinout

Important

MT-System, one of the largest suppliers of radio-electronic components in Russia and the CIS, is the only company that officially supplies SIM chips to the Russian electronics market. For quick testing of SIM chips, MT-System offers developers “SIM-chip-adapter” adapter boards, similar in shape and size to SIM cards (Fig. 6). The adapter board with a SIM chip soldered onto it fits into most SIM card holders and does not interfere with the elements of the holder.

Since the sizes and pinouts of SIM chips are standardized, the “SIM chip adapter” can be used together with the SIM chip of any cellular operator. Rice. 6.

GSM SIM card pinout

In addition, there is no hole in the case for a SIM card holder, which means that the device is waterproof and, importantly, vandal-resistant - it is impossible to remove the SIM chip from it in order to insert it into a standard slot of a mobile phone, which eliminates the possibility of inappropriate traffic consumption. SIM chip access to cellular communication services The process of replacing SIM cards with SIM chips is a new direction in the Russian M2M electronics market, coming from the West. Today, all major Russian cellular operators have already mastered working with them and are ready to connect SIM chips built into any GSM device.

The life cycle of a device that uses a SIM chip can be divided into two parts - before the sale and after the device is sold to the end user.

SIM card connector pinout

C7 I/O Input or Output for serial data (half-duplex) to the integrated circuit inside the card. C8 RESERVED AUX2, optionally used for USB interfaces and other uses. Please note that there are great variations in connector shape: Image from Wikipedia: The dialogue between the interface device and the card shall be conducted through the consecutive operations:

• connection and activation of the contacts by the interface device
• reset of the card
• answer to reset by the card
• subsequent information exchange between the card and the interface device
• deactivation of the contacts by the interface device

Interfacing smart card isn't a simple task. Here is the Smart card to PC interface adapter cable scheme.

SIM card slot pinout

The ROM memory is written by the mobile operator operating system, IMSI code, which is unique and provides identification of the SIM card on the network, an individual key Ki, designed for encryption (to be more precise, using the key Ki and the generated random number Using the A8 algorithm, a 64-bit key Kc is created. The Ki key is stored on a specific SIM card and in the operator's database, kept secret and never transferred between the operator and the subscriber, and the Kc key is used to encrypt data transferred between the cell phone and the network base station). Encryption algorithms and some other codes are also entered into the ROM, including a list of allowed networks (TMSI codes - Temporary Mobile Subscriber Identity, LAI - Location Area Identification), PUK - Personal Unblocking Key for unlocking the SIM card in case of entering the PIN incorrectly three times -code.

Once upon a time, more than 20 years ago, which by the standards of the modern IT industry can even be considered untrue, mobile phones used special numbers recorded in them at the factory to identify themselves in the cellular provider network. However, this approach was not very convenient for both users and manufacturers. They were interested in "separating" the subscriber ID from the hardware. This is how the idea of ​​using additional individual cards with built-in microcircuits arose. This approach is used today in networks of various standards - GSM, CDMA, UMTS, LTE, but we will talk mainly about the most widespread option - GSM/3G.

The telephone device, as a physical device, has an IMEI (International Mobile Equipment Identity) number, which can be considered unique on a global scale. It participates in transaction logs mobile operator and, in principle, can be used to block network access, search for stolen phones and other similar actions. In some countries, it is illegal to falsify or change this number. The IMEI number can usually be found on a sticker under the battery and on the box. From a technical point of view, it is written electronically in one of the microcircuits and, of course, can also be read programmatically. If the telephone has the ability to install multiple SIM cards, then IMEI numbers several too. This number is available not only for phones, but also for modems, tablets and other devices designed to work in mobile networks. Formally, manufacturers could get by with just this number and not use traditional serial numbers for their products, but today this “separate” approach is more convenient for them.

A similar SIM card number is called ICCID (Integrated Circuit Card Identifier). It is often engraved on the cards themselves. It is similar to the serial number of the device - the only difference is that it is unique and cannot be repeated on any other card in the world. Although if to serial number phone also include the manufacturer and model name, then this combination will also be unique.

Direct identification of the subscriber in the cellular network takes place using the IMSI (International Mobile Subscriber Identity) number, which is recorded in the SIM card. This number determines the ownership of the card by the operator and allows you to link the card user with his account with the provider, including the phone number, permitted services, and so on. The card also stores other unique information, the description of which is beyond the scope of this article.

A few words should be said about card protection. The first milestone is a four-digit PIN code. If you do not know him, you will not be able to use the card to access cellular network or to read a notebook. The user can change or cancel this code (it is usually disabled on newly purchased cards). If the PIN code was entered incorrectly several times, to unlock it you need to use the PUK code, also provided by the operator along with the SIM card. Even less commonly used are PIN2 and PUK2 codes, which allow the user to limit the list of allowed subscribers for outgoing calls.

But even if you know all these codes, you won’t be able to copy the card using everyday methods. There is another special code written inside it, known to the operator, which is used in the identification algorithm. This process is designed in such a way that the pure code is not transferred from the card to the phone. Instead, the device sends a task to the SIM card processor to encrypt the key, and transmits the response to the operator. The latter compares the result with that received in its data center, and if they match, the subscriber gains access to the network.

One of the popular options for “full-size” smart cards today

Technically, a SIM card is one of the variants of smart cards - microcomputers with their own processor and memory that communicate with outside world through an interface of several electrical contacts. Smart cards are found today in banking sector, are used for access control and in various payment systems. Usually the card has several kilobytes of permanent memory, a couple of kilobytes random access memory and a little flash. In the case of phones, the latter was previously used to store a notebook, but the limit on the number of entries (250) and support for only two fields (name and phone) has practically deprived it of this role today.

Electronic filling takes up very little space

Formally, the card has eight contacts for connecting to a reader (if you try really hard, you can try to count more). However, in reality only six are used. And given modern progress in microelectronics, the filling takes up literally a few square millimeters.

But if we talk about external dimensions, then it all started with a credit card format - 85.6 × 53.98 × 0.76 mm. This format Smart cards are still used today, but they stopped satisfying the wishes of cell phone manufacturers a very long time ago. Much more practical is the Mini-SIM version, which measures 25x15 mm with a beveled corner (to determine the required orientation of the card in the slot). The thickness did not change. It is this format that is the most widespread today and is found in most cell phones.

Mini-SIM and Micro-SIM cards use much less plastic

It is clear that such a reduction did not bring any losses in terms of functionality. But you need to understand that Mini-SIM is good specifically for placement in a telephone body. Using a card of this size, for example, for payphones, is obviously inconvenient.

After the massive transition to the Mini-SIM format, for a very long time it remained practically the only option for use in the field of mobile communications. Even successes in reducing the external dimensions of telephone sets did not require further reduction of the subscriber card. But still, he was not allowed to gain a foothold for centuries.

Special frames can be used to install Micro-SIM (sometimes Mini-SIM)

One of the most active market players in its new smartphone model two and a half years ago implemented work with the Micro-SIM format, the dimensions of the cards are 15x12 mm (the thickness has not changed again). For cards of this format, almost the entire front surface was occupied by contact pads. But there were no technical difficulties for him to place the chip, especially with the development of chip manufacturing technologies. Note that, from a consumer device design perspective, the market did not require this step. So, rather, the company played in the field of marketing, once again repeating “we are not like everyone else.”

Electronic “filling” takes up very little space even in Mini- and Micro-SIM

Interestingly, this year the same manufacturer played this card again. The latest model of their smartphone works exclusively with Nano-SIM, in which the thickness has already been reduced - 12.3 × 8.8 × 0.67 mm. Eight standard contacts no longer fit into this format, so only six truly working ones remain. None technical functions the cards were not affected this time either, but the size of the new phone was not as reduced as one might think (and some even increased).

Almost the entire front surface of Nano-SIM is occupied by contact pads

A very reasonable question arises: how does this miniaturization story affect consumers? If we talk about those who buy a new phone with a contract and a new card, they usually don’t care what version of the SIM card is installed in it. And if a person basically has only one phone or he doesn’t plan to rearrange cards, then it’s not even “usually”, but “absolutely”.

To install Micro-SIM in the Mini-SIM bay, you can use adapters

But for those users who are accustomed to using several devices and/or SIM cards, the situation is less pleasant. In the case of a Mini/Micro pair, you can try to make do with so-called adapters/adapters (of course, after replacing all Mini format cards with Micro format cards). There are no advantages to this story, only disadvantages - you need to carry additional parts with you, and in addition, the adapter can damage the connector contacts during replacement (or the assembly may even get stuck in the slot).

As for changing cards, then official way consists of visiting your operator’s salon, writing an application, waiting and all that. In addition, if you suddenly have some entries on the card, you will need to take care of saving them. More available option from a time-consuming point of view, go to numerous workshops, where your card will be cut with a special tool in a couple of seconds (by the way, large salons and even the operators themselves do this). If you really don’t want to go anywhere, then a sharp knife and a strong hand can also successfully solve the problem. For the first time, a printout from the Internet with a “cutting” diagram may be useful (see, for example,).

With Nano-SIM the situation is more complicated, since both the linear dimensions and thickness of the card are smaller. The methods remain the same. But at present the first of them should be recognized as the most correct. However, given the prevalence and cost of the device, for which you may need a Nano-SIM, this should not be a problem.

A smart card, chip card, or integrated circuit card, is a pocket-sized card with embedded integrated circuits. Described by ISO7816 standard. Used in cellular phones, pay TVs, ATM cards, etc.

There are two broad categories of ICCs. Memory cards contain only non-volatile memory storage components, and perhaps dedicated security logic. Microprocessor cards contain volatile memory and microprocessor components. A smart card, chip card, or integrated circuit card (ICC) is any pocket-sized card with embedded integrated circuits.

Smart cards can provide identification, authentication, data storage, strong security authentication for single sign-on (SSO) and application processing.

Physical, electrical and other characteristics of Smart cards are described by the ISO/IEC 7810 and ISO/IEC 7816 series of standards.

Smart Card (SIM Card) pinout

Pin	Name	Description
C1	VCC	+5 VDC power supply input (optional use by the card)
C2	RESET	Reset signal, used to reset the card's communications. Either used itself (reset signal supplied from the interface device) or in combination with an interal reset control circuit (optional use by the card). If internal reset is implemented, the voltage supply on Vcc is mandatory
C3	CLOCK	Provides the card with a clock signal, from which data communications timing is derived
C4	RESERVED	AUX1, optionally used for USB interfaces and other uses.
C5	GND	Ground (reference voltage)
C6	Vpp	Programming voltage input (optional). This contact may be used to supply the voltage required to program or to erase the internal non-volatile memory. ISO/IEC 7816-3:1997 designated this as a programming voltage: an input for a higher voltage to program persistent memory (e.g., EEPROM). ISO/IEC 7816-3:2006 designs it SPU, for either standard or proprietary use, as input and/or output.
C7	I/O	Input or Output for serial data (half-duplex) to the integrated circuit inside the card.
C8	RESERVED	AUX2, optionally used for USB interfaces and other uses.

Please note that there are great variations in connector shape:

Image from Wikipedia:

The dialogue between the interface device and the card shall be conducted through the consecutive operations:

• connection and activation of the contacts by the interface device
• reset of the card
• answer to reset by the card
• subsequent information exchange between the card and the interface device
• deactivation of the contacts by the interface device