Types of SIM cards: sizes, cropping. SIM cards - functions and features Purpose of a sim card
Subscriber identification in the network was carried out by the manufacturer's cell phone number - ESN (Electronic Serial Number). Thus, both the cell phone and the subscriber were identified by a single code. This approach gave rise to a complete dependence of the subscriber's number and the package of services provided to him on a specific phone instance. Having changed the cell phone (including cases of breakdown and theft of the phone), the subscriber was forced to contact the operator's office in order for the phone to be reprogrammed and its serial number entered into the operator's database, which some operators did for a fee.
It is obvious that the identification of the subscriber, independent of the phone, is more convenient. In the GSM standard, it was proposed to separate the identification of the subscriber (using a SIM card) and equipment (for this, IMEI is used - the international identifier of mobile equipment).
Standards
The GSM SIM card is a variation of the regular ISO 7816 smart card. The standard for the specific features of a GSM SIM card is established by GSM 11.11, GSM 11.14 and GSM 11.19 documents. Modern cards have the ability to execute applications on the card, and therefore support JavaCard functionality.
In connection with attempts to integrate RFID technologies into cell phones, SIM cards are also proposed to be equipped with a second Single Wire Protocol physical interface for direct communication with the NFC physical layer chip.
Functions and characteristics
The main function of the SIM card is to store identification information about the account, which allows the subscriber to easily and quickly change cell phones without changing his account, but simply by moving his SIM card to another phone. To do this, the SIM card includes a microprocessor with software and data with card identification keys (IMSI, etc.), written to the card at the stage of its production, used at the stage of card (and subscriber) identification by the GSM network.
Also, the SIM card can store additional information, for example:
- subscriber's phone book
- lists of incoming/outgoing/missed phone calls
- text of incoming/outgoing SMS .
In modern phones, most often this data is not written to the SIM card, but is stored in the phone's memory, since the SIM card has quite strict restrictions on the format and amount of data stored on it.
The SIM card contains a memory chip that supports encryption. There are cards of different standards, with different memory sizes and different functionality. There are cards on which additional applications (applets) are installed during production, such as a SIM menu, telebank clients, etc.
The subscriber's telephone number (MSISDN) is not explicitly stored on the card itself, it is assigned by the operator's network equipment when registering a SIM card on the network based on its IMSI. According to the standard, when registering one SIM-card in the network, the operator can assign several phone numbers to it. However, this possibility requires appropriate support by the operator's infrastructure (and corresponding costs on his part), therefore, it is most often not used.
If the SIM card is lost, the subscriber must notify the operator, the lost card is blocked, and the subscriber is issued a new card (for a fee or free of charge, depending on the conditions of the operator). The phone number, balance and all connected services remain unchanged, but all subscriber data stored on the SIM card cannot be restored.
The SIM card is installed in the cell phone's SIM holder, which in modern cell phones is usually located under the battery. The location of the SIM holder under the battery does not allow you to install / remove the SIM card when the phone is powered on, because this can damage the card.
Formats and sizes of SIM cards
SIM cards have gradually decreased in size over several decades, but retained functionality and compatibility regardless of format. Initially, the cards were issued in full-size format, then in the form of mini-SIMs. Since the mid-2000s, micro-SIM cards have been introduced. Since the early 2010s - nano-SIM. Sometimes, for example in M2M devices, the functions of SIM cards are implemented by a microcircuit built into the device.
| SIM card format | Year of appearance | Standards | Length (mm) | Width (mm) | Thickness (mm) | Volume (mm 3) | Cellular generation |
|---|---|---|---|---|---|---|---|
| Full size (1FF) | 1991 | ISO/IEC 7810:2003, ID-1 | 85,60 | 53,98 | 0,76 | 3511,72 | |
| Mini-SIM (2FF) | 1996 | ISO/IEC 7810:2003, ID-000 | 25,00 | 15,00 | 0,76 | 285,00 | 2G, 3G |
| Micro SIM (3FF) | 2003 | ETSI TS 102 221 V9.0.0, Mini-UICC | 15,00 | 12,00 | 0,76 | 136,80 | 3G, 4G |
| Nano SIM (4FF) | 2012 | ETSI TS 102 221 V11.0.0 | 12,30 | 8,80 | 0,67 | 72,52 | 3G, 4G |
| Embedded SIMs | JEDEC Design Guide 4.8, SON-8 | 6,00 | 5,00 | < 1,0 |
Next generation SIM cards (5FF, eng. eUICC) are being worked out, which probably will not be replaceable.
SIM-cards are usually issued in the form of larger plastic cards, from which a Mini/Micro/Nano format module is removed (“broken out”) according to a prepared template.
Micro SIM
Micro SIM- Created in 2003, a miniature alternative to the SIM card for identifying subscribers on mobile devices. The physical size of the card is 12×15 mm. The micro-SIM is smaller than the mini-SIM previously used in mobile devices, but the contact plate and exchange interface are usually identical. Therefore, in most cases, you can get a micro-SIM from a mini-SIM by cutting the plastic case.
Nano SIM
The Nano-SIM (4FF) format with dimensions of 12.3x8.8x0.67mm was introduced in October 2012. Such cards have become even smaller than previous formats and at the same time retained the location of contacts. They are also 12% thinner than the previous 0.76mm version. With a 4FF adapter, the card can be used as 2FF or 3FF.
The first devices to use nano-SIM were the iPhone 5, released in September 2012.
e-SIM
GSMA proposed to radically solve the problem of miniaturization of mobile devices in 2014 in the form of Remote SIM Provisioning technology. As part of this technology, it was proposed to solder a SIM card in the form of a microcircuit into the device at the stage of its manufacture (hence the built-in SIM, embedded-SIM, e-SIM). The mobile operator gives the client not a SIM card, but a set of encrypted data that the client enters into his device. The new technology will allow not only to abandon slots for SIM cards and the cards themselves, but also to install several operator profiles in one device, solving the problem of several SIM cards.
Virtual SIM
Virtual SIM is the common name for a variety of non-standard technical solutions that allow you to remove a SIM card from a mobile phone. The SIM card is installed in a special device connected to the Internet (for example, a modem, another cell phone, a special SIM card server) or connected to the user's cell phone via a wireless channel (for example, Bluetooth). Software is installed in the user's mobile phone, which, when requested by the mobile operator, redirects this request to the SIM card via the Internet or another communication channel.
This technology can be used to quickly switch between multiple SIM cards, redirect calls between service regions, simplify and reduce the mobile communication device by eliminating the SIM card slot.
Multisim cards
Multisim cards ( "MultiSim") - devices in the form of a regular SIM card (GSM standard) and consisting of a microprocessor (PIC-processor PIC16F877) and an additional memory module (24C64 - 24C256). The microprocessor operates under the control of a special firmware (SIM-EMU 6.01), which also performs the functions of a conventional SIM card. This concept makes it possible to write the necessary data to the MultiSim card from several SIM cards at once and use the number that is most convenient at the moment. You can select the desired number in a special menu (using technology SIM Tool Kit) or when entering the PIN code of the desired number .
PIN code
When a SIM card is issued, it is assigned a four-digit PIN code, which is written to the card and also transmitted to the subscriber along with the card.
When enabled, the PIN code will be requested by the phone each time it is turned on in order to access the data on the SIM card. In the 2010s, the option is disabled by default in most SIM cards released.
If the PIN code is entered incorrectly three times in a row, the card is blocked and can only be unblocked by entering the personal unblocking code PUK1 ( PIN Unblocking Key), which is also transmitted to the subscriber along with the card. If the PUK code cannot be entered correctly after ten attempts, then the SIM card is completely blocked and must be replaced. The user can also change the PIN using the PUK code.
Some SIM cards have a second set of PIN codes: PIN2 and PUK2 to work with several additional services.
If the SIM card is not installed in the phone or if the correct PIN is not entered, the phone cannot make any calls on the cellular network, except for emergency calls (number 112 or 911). All other functions of classic phones are usually blocked, however, smartphones and communicators are able to work in such conditions.
ICCID
Examples of Issuer Identification Number:
- Beeline: 89 7 0199
- MTS: 89 7 0101
- MegaFon: 89 7 0102
- Tele2: 89 7 0120
- MTS Ukraine: 89 380 01
SIM Tool Kit
Criticism
Data recovery
Work with data (contact numbers, SMS messages, etc.) stored on the SIM card takes place via the phone. However, when deleting this data through the phone, they are not completely deleted, but only marked as deleted, which means that they can be restored. To recover deleted data (as well as completely delete them) from a SIM card, there is specialized software, for example, Device Seizure from Paraben Corporation.
Vulnerabilities
In 2011, Security Research Labs, led by Karsten Nohl, began testing the security of SIM cards. The result of two years of work was the identification of the vulnerability of SIM cards on the outdated DES crypto algorithm, due to which you can get full access to the contents of the SIM card. According to this study, on July 31, 2013, Carsten Nohl presented his paper at the BlackHat conference.
Notes
- New SIM standard adopted: nano-SIM (unavailable link)
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 stored in them at the factory to self-identify in the network of a cellular provider. However, this approach was not very convenient for both users and manufacturers. They were interested in "separating" the subscriber ID from the equipment. 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 mainly talk about the most popular option - GSM / 3G.
The telephone set, as a physical device, has an IMEI (International Mobile Equipment Identity) number, which can be considered unique on a global scale. It participates in the logs of the cellular operator's operations and, in principle, can be used to block access to the network, search for stolen phones, and other similar activities. In some countries, it is illegal to forge and 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 recorded electronically in one of the microcircuits and, of course, can also be read by software. If the telephone set has the ability to install several SIM-cards, then there are also several IMEI numbers. 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 such a “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 - with the only difference that it is unique and does not repeat on any other card in the world. Although if you add the manufacturer and model name to the serial number of the phone, then this combination will also be unique.
The direct identification of the subscriber in the cellular network is carried out by the IMSI (International Mobile Subscriber Identity) number, which is recorded in the SIM card. This number identifies the operator's ownership of the card and allows you to associate the card user with his account with the provider, including a phone number, allowed 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 the protection of cards. The first frontier is a four-digit PIN code. If you do not know it, you will not be able to use the card to access the cellular network or to read a notebook. This code can be changed or canceled by the user (it is usually disabled on freshly purchased cards). If the PIN-code has been entered incorrectly several times, to unblock it, you need to use the PUK code, also provided by the operator along with the SIM card. Even more rarely, PIN2 and PUK2 codes are used, 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 household methods. Inside it is recorded another special code known to the operator, which is used in the identification algorithm. This process is arranged in such a way that the code in its pure form 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 passes the answer to the operator. The latter compares the result with the one obtained in its data center, and if they match, the subscriber gets access to the network.
One of the most popular variants of "full-size" smart cards today
Technically, a SIM card is one of the options for smart cards - microcomputers with their own processor and memory that communicate with the outside world through an interface of several electrical contacts. Smart cards are found today in the banking sector, are used for access control and in various payment systems. Typically, the card has a few kilobytes of permanent memory, a couple of kilobytes of RAM and some 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) have practically deprived it of this role today.
Electronic stuffing takes up very little space
Formally, the card has eight contacts for connecting to the reader (if you try hard, you can try to count more). However, only six are actually used. And given the modern progress in microelectronics, the filling takes just 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 of smart cards is used today, but it has ceased to satisfy the wishes of cell phone manufacturers for a very long time. Much more practical is the Mini-SIM version, which measures 25x15mm with a bevelled corner (to determine the proper orientation of the card in the slot). The thickness has not changed. It is this format that is the most popular 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 for placement in the body of the telephone. Using a card of this size, for example, for payphones, is obviously inconvenient.
After the mass transition to the Mini-SIM format, for a very long time it remained almost 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)
Two and a half years ago, one of the most active market players in its new smartphone model implemented work with the Micro-SIM format, the dimensions of which are 15 × 12 mm (the thickness has not changed again). For cards of this format, almost the entire front surface was already occupied by pads. But there were no technical difficulties for him to place the chip, especially with the development of chip manufacturing technologies. Note that, in terms of consumer device design, the market did not require this step. So, rather, the company played in the field of marketing, repeating once again "we are not like everyone else."
Electronic "stuffing" 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 really working ones remain. No technical features of the card were affected this time around, but the dimensions of the new phone are not as reduced as one might think (and some even increased).
Almost the entire front surface of the Nano-SIM is occupied by pads
A 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, then they usually do not care what version of the SIM card is installed in it. And if a person has, in principle, one phone or he does not plan to rearrange cards, then not even “usually”, but “perfectly”.
Adapter adapters can be used to install a Micro-SIM into a Mini-SIM bay
But for those users who are used to using multiple handsets and/or SIM cards, the situation is less pleasant. In the case of a Mini/Micro pair, you can try to get by with the so-called adapters/adapters (of course, after changing all Mini format cards to Micro format cards). There are no pluses in this story, only minuses - 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, the official way is to visit the salon of your operator, write an application, wait and all that. In addition, if suddenly you have some records on the card, you will need to take care of saving them. A more affordable option in terms of time consumption is to contact 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 at all, then a sharp knife and a strong hand are also able to successfully solve the problem. For the first time, a printout from the Internet with a “cutting” scheme may come in handy (see, for example,).
With Nano-SIM, the situation is more complicated, since both the linear dimensions and the thickness of the card are smaller. The methods remain the same. But the most correct at the present time is to recognize the first of them. However, given the prevalence and cost of the device, for which you may need Nano-SIM, this should not be a problem.
Mobile communication has become our faithful companion. It's hard to imagine a car ride, a commute, a job, or even a trip to the store without a cell phone. The tube becomes a lifesaver in any difficult situation. A person is used to his little 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 to take your cell phone with you for a couple of days. Thoughts of missed appointments, possible trouble while driving, or meeting anxiety will overwhelm you. So 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? The cycle of our articles "Secrets of communication" should change this. We will introduce you to many interesting moments in the life of cellular communications and give you a basic understanding 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 on a par with 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 possibilities of which are far from being fully utilized.
Why a SIM card?
The history of any device is closely related to the question - "Why"? They say that if a child asks it at the age of 2, then a genius grows out of him. If the cherished word is uttered at the age of five, then we have a simple individual. It becomes excruciatingly painful when you think 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 question.
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 is the key to the provision of all services. During connection to the network, the handset receives a unique designation, which is entered in a special register. The issue of assigning a code to each phone at first was solved 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 automotive industry. It is no secret that earlier in many countries a license plate was assigned to a car at the factory and accompanied the car throughout its life (do not confuse it with a body number or VIN number). Such an approach is entirely justified, even in spite of the obvious problems associated with the necessary agreements on formats and common databases. So, the first phones were on the network under their Electronic Serial Number (ESN). Problems appeared very soon. 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 differ in warm relations with each other, like any normal competitors in a dynamically developing market. Therefore, it became almost impossible to agree on uniform formats for the Electronic Serial Number (ESN). Of course, after some time this chaos would be ordered. However, the thunder that struck from the side of the users did not give development to this scenario. The fact is that in those days, visiting a mobile operator for registration with him and other formal manipulations became a heavy duty of the subscriber. Cellular communication, which looked and was presented as a sprout of freedom, appeared as a heavy burden. In a word, Electronic Serial Number (ESN) did not suit a certain audience in the bud. All forces were thrown in search of alternative ways. They have been found. In fairness, I note that even now a number of networks in the world use the Electronic Serial Number (ESN) to identify the subscriber, but there are no visible prospects in this direction and this approach is doomed to extinction. So, with the designated problem coped very interestingly. It was decided to separate the identification of a cell phone and a subscriber. At first it looked very attractive. Over time, there were shortcomings, 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 IMEI (International Mobile Equipment Identifier) number. There are special services that monitor and distribute ranges of numbers for development companies. If you are familiar with the computer business, then this is an analogue of the MAC address of the network card. So, the cell phone is identified by the operator by the IMEI code. But the subscriber is separated from the cell phone. The SIM card is used to identify it. This device becomes an indispensable companion of all your negotiations (except for calling emergency services by number 112, which is carried out 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;
- the possibility of programming;
- finished goods
Stages of SIM-card development
|
Time stage |
The evolution of the SIM card |
|
|
SIM card memory and supply voltage |
SIM card features |
|
|
1991-1993 |
8 KB, 5.5 Volts |
incoming and outgoing calls, call forwarding, call barring, call waiting, card lock, network selection PLMN (roaming feature), SMS (receive only), speed dialing, sending and receiving faxes, prohibition of networks without a roaming agreement - FPLMN. |
|
1994-1997 |
8 KB; 5.5 and 3.3 Volts |
Support for all functions of the previous window plus additional ones - PIN2 (protection of data fields), fixed dialing, SMS (added the ability to send), SMS status, last number autodial, menu language selection, message personalization, support for multiple numbers (voice, digital, fax ), repeating the last dialed number, 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 date |
16 KB, 64 KB, 3.3 Volts; 1.8 Volts |
It is in the process of formation. Added more than 50 new features. Among them (the most interesting and promising) are SIM Application Toolkit, Enhanced Full Rate, as well as the interaction of GSM and DECT. Java support. |
One simple pattern can be traced - the SIM card is becoming a more technological solution. The amount of memory grows along with the feature set. What awaits us in the future? First of all, a jump in SIM card memory expansion is possible. Developers and engineers have repeatedly reported that they are ready to introduce 1 MB SIM cards 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 an obvious benefit. Doubts come from the market of flash memory cards. 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 buying, the subscriber will not have to overpay for extra free space. And yet there is information that is not handy to take away from the SIM card, and the latter will still grow in digital volume. The second obvious step is to lower 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, as the power spent on the operation of the SIM card becomes smaller.
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 that can store various information. It meets all ISO 7816 specifications and operates under T=0 protocol class ISO A0h. Before us 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, the mobile operator may, through the message sent to you, add or remove new menu items to your phone.Now it has become clear how the operator creates new services on your phone. Everything is very simple. The situation resembles the work of a conventional computer. Remember that if the SIM card is removed from the handset, then the information on it cannot be lost. On the other hand, it shouldn't surprise you that removing or changing your SIM card can change your phone's menus. Let's take a quick look at the memory structure of a SIM card. The MF (Master File) root directory 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 a subscriber's IMSI code, a list of supported languages, a table of available services, etc. The file consists of a header (header) and a body (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 (records) of a fixed length and, in accordance with this, should be considered as sequential. The maximum size of such a file is 255 records per 255 bytes, not counting the extension.
- A cyclic file contains a certain number of fixed length records. In this case, each new record always occupies the first position, while the last one is "overwritten".
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 crash sometimes? The SIM card is no different from it...
SIM protection and failures
The owner of the SIM-card gets the opportunity to make calls, send information or use other services. Its correct identification becomes the key to spending money. And where there are voiced coins, you should definitely expect unscrupulous people who will try to rob you. Such 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 watchmen are our best friends in this world. The SIM card also has its own lock. The key to it is Personal Identification Number - PIN code. It is received by the user when buying a card. You can enable all (almost) functions of the SIM card only by typing it correctly. In case of an error (the user is given a three-time attempt), 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). PIN and PUK code was originally planned to be set from 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 that, the device does not require the owner to enter a PIN code when switching on or other related events. There are also PIN2 and PUK2 codes. They help to reveal additional features of the SIM card. For example, they initialize commands to bar incoming or outgoing calls. Removing this code is also possible and the responsibility for this step lies with the subscriber. Most often, according to the statistics of service departments, failures in the operation of SIM-cards occur after their mechanical damage. The culprit of our review is very fragile. Modern cell phones are getting hard grips for SIM cards. Users diligently break them in the stubs. Replacing a broken SIM card is easy, but restoring content is often impossible. The second most common problem is associated with forgetting the PIN. After entering it three times, the phone is blocked. A dozen unsuccessful attempts to enter PUK and the SIM card turns into trash. On the screen of the cell phone, an invitation appears to visit the operator to replace the SIM card. 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 to clean its contacts (ethyl alcohol will help to do this, but don't equate cleaning delicate gold contacts with removing rust from an old sheet of iron) and reinstall it in the mobile device. If the situation does not change, then feel free to go to the operator. Your SIM card, like any computer, has the right to fail. 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 information on the SIM card will be hopelessly lost for you. Personal experience suggests that all requests to restore it stumbled upon a wall of misunderstanding and an unequivocal assurance that it was impossible to do this and that this was not spelled out in the contract.Attackers and your SIM card
Is it possible to clone SIM cards? Theoretically, this process is solved quite simply. An attacker must copy service information from a SIM card (International Mobile Subscriber Identity (IMSI), its individual encryption key (Ki) and cryptographic algorithm program (A3)) onto an empty disc. Thus, an absolutely identical clone will appear on the network, which will be able to spend money on a par with the original. Is it possible for a full clone to exist on the network? A number of operators absolutely confidently answer that such a possibility is completely excluded. A subscriber with a double (one-time online presence) will be instantly disconnected until all circumstances are clarified. Indeed, operators keep the register of users very strictly. It is not difficult to catch multiplied subscribers. However, an experiment was recently conducted (we deliberately keep silent about the operators and countries of this experiment) to clone SIM-cards. It turns out that some operators do not have protection for this case. Blind confidence in the impossibility of cloning users of GSM networks can play into the hands of attackers. How to clone a SIM card? Theoretically, this is enough to intercept a large data packet on the air. After that, extract the necessary data from there. In reality, this method does not work. There is no way to force the phone to broadcast as much as necessary. Therefore, you should only be afraid of the direct theft of your SIM card. Devices for reading and writing them can be bought in any major city without any licenses. Making a double 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
To summarize: a SIM card is an ordinary microcomputer. It is the heart of your cell phone and, unfortunately, the device is not without sin - it can break. In our review, we focused on the story about the SIM-card for GSM networks. Devices that are used in satellite phones or networks of other operators are almost identical at the basic level. They may differ in memory size, command set, service information, and so on. In our next article, we will tell you about how GSM communication is built in modern networks.All questions, comments and suggestions can and should be asked in
Every year our smartphones become more functional, resembling computers rather than telephones. And only one common feature remains unchanged - the presence of a SIM card. It consists of a chip surrounded by plastic, and its main purpose is to recognize a subscriber in a mobile communication network. Smartphones have an interesting trend - to change in size, becoming more and more thin and practical. Similar processes occur with a SIM card - the amount of plastic is constantly decreasing, making room for new elements in devices.
Being an integral part of our gadgets, the SIM card changes its appearance along with the development of technology. Before proceeding directly to trimming a SIM card, let's look at its types:
Mini-SIM cards have been very popular for a long time
Micro-SIM rid itself of excess plastic
Nano-SIM is the smallest SIM card in existence.
eSIM chips will not be removableTable: types of SIM cards
Having an idea about the existing SIM-cards, as well as their appearance and size, let's go directly to the use of SIM in Apple products.
Table: Using SIM cards in Apple devices
How to cut a SIM card for the desired phone model
Having determined the desired type of SIM card, we proceed directly to the process of cutting the card, if necessary. As tools you will need:
The sequence of actions is as follows:
Marking is a very responsible process, it is important not to make mistakes when drawing lines
It is necessary to compare the size of the slot with the intended markup
Unnecessary plastic is cut off with gentle movements
As a result, the SIM should easily fit into the card slotVideo: cutting a SIM card to the desired size
At first glance, the described process may seem complicated. However, following all the instructions, you will definitely get the perfect result and your SIM card will last a very long time.
The most popular microcomputer
It is no longer easy to surprise someone with a microcomputer today - they surround people everywhere. And these are not only various "handhelds" - PDAs or calculators, but also numerous microcontrollers of automation equipment, which are already penetrating with might and main into ordinary household appliances. But all these devices, produced by a large number of companies, have different architectures and parameters. But the most common model is a product, most of whose users do not even suspect that this is a microcomputer. He is located in SIM cards used in GSM cell phones, and the number of owners of such phones on our planet is already approaching a billion people!
The emergence of SIM cards
are integral parts of GSM cell phones, but phones of many other standards do well without them. Why were they needed?
To identify phones in the GSM standard, a special 15-digit unique number of the International Mobile Equipment Identifier (IMEI) is used, assigned to each device during production (it is also written on the packaging box and on the phone itself - under the battery) and reported by it to the cellular network at the beginning of the exchange.
Basically, SIM card could be made as simple as possible and contain only the subscriber's identification number. But its creators went the other way and immediately implemented in it functions related not only to subscriber identification, but also to card authentication (authentication) and encryption of negotiations. In other words, the entire set of functions performed directly by the phone in other standards is divided in GSM between the device itself and SIM card. All purely "connected" operations (reception and transmission of signals, their modulation and detection, reproduction of sounds and display of characters on the display, etc.) are performed in the phone, and everything related to personal data is implemented in SIM card. As a result of this approach, a perfectly serviceable GSM phone on its own (without) provides the ability to make only "SOS" calls (usually according to the international code) to emergency services: police, firefighters, medical assistance, etc. - this requirement was originally laid down in the standard . On the other hand, the need to perform SIM card information processing operations led to its implementation on the principle of a specialized computer running its own operating system and containing all the main elements of a microcomputer: an 8-bit processor, information input and output nodes, as well as permanent (ROM), operational (RAM) and reprogrammable (EEPROM) memory. It is in non-volatile, but variable EEPROM memory (in modern SIM cards it has a capacity of up to 64 kb), and all application information is placed - both user and service.
In terms of their computing power, they are quite comparable with the first personal computers of the eighties of the last century, and the achievements of modern microelectronics make it possible to constantly increase their capabilities. As a result of this, in SIM cards many other functions began to be implemented: notebooks with a capacity of up to 100 or more phone numbers with names, lists of recent calls made and received, etc.
Truly revolutionary changes in any phone that supports the development phase of the GSM 2+ standard (almost all models released after 1998 fall here) are made by a technology created several years ago SIM Application Toolkit (STK). It is based on the widespread use of SMS messages for information exchange and is a special software application recorded on SIM card in the form of sets of executable procedures and commands. Under the control of such programs, the phone becomes able to automatically perform various sequences of actions. This can be a call to a certain number, sending a short message to a certain number and with a certain content, sending an e-mail or fax, etc. All these procedures, of course, can be performed manually, but automating the process greatly simplifies and speeds up the use of such services. . These may include: access to information and reference services (weather forecast, exchange rate, latest news, traffic conditions, etc.), control of connection and disconnection of used cellular network services, Internet access, payment for various services with mobile phone, games, etc.
Purely technically, they are a variety of chip smart cards adapted to the needs of mobile communications, the parameters of which are set by a group of international standards ISO 7816. Such cards were originally focused on use in payment systems and therefore, even at the development stage, special attention was paid to the reliability of their a wide variety of conditions, sufficient mechanical strength and high resistance to electrical stress, magnetic fields and other influences. In this regard, they rarely fail, and if suddenly the phone refuses to work with the card, then you must, first of all, find out what the phone "does not like".
The reasons here may be different, and the phone always displays a corresponding message about them on the display. So, for example, if SIM card blocked by a special code of the subscriber's personal identifier - Personal Identification Number - PIN (protects the phone from unauthorized use by unauthorized people), then a message like "Enter PIN code" will appear on the phone screen. During manufacture, this code (4-8 characters) is set individually for each and issued to the user along with the card (although sometimes it is set by manufacturers and is the same for entire groups of cards at once, and at the same time even extremely simple: "0000"). The PIN code is entered directly from the phone keypad, and if you make a mistake in typing the code, you can repeat it, but no more than 3 times. If all 3 times the PIN code was entered incorrectly, SIM card enters the state of temporary blocking and now requires entering the 8-digit code of the personal unlock key - Personal Unblocking Key (PUK), which is also issued to the user upon sale of the card. You must enter it carefully, because after ten erroneous attempts to enter the PUK code SIM card is blocked completely and its replacement is required, about which a message appears on the phone screen with a recommendation to contact the mobile operator. If the blocking was successful, then the value of the PIN code can be changed at any time by the user himself. The PUK key, on the contrary, cannot be changed. In addition to PIN and PUK codes, there is also a similar pair of PIN2 and PUK2 codes (also contained in the documentation for SIM card received by the user), which are used to control access to certain functions (barring incoming and outgoing calls, resetting the call duration and cost counter, etc.). Entering the PIN2 code incorrectly three times disables these features and requires the PUK2 code to be unlocked. PIN and PIN2 codes, as well as PUK and PUK2 codes, should not be confused - they have different meanings and perform different functions.
For a completely different reason, when you turn on the phone, the message "Insert SIM card". If it is not in the phone, then it is clear what needs to be done, but if the card is installed, then such a message means that the phone "does not see it". Most often, this can be caused by a trivial bad contact between the card and the phone. Actions here may be the following.First of all, you need to try to remove SIM card and put it back in place again. If after that the phone did not start working, then you can try to rinse the contacts on SIM card and in the phone jack with ethyl alcohol or special cleaning liquid and lightly wipe with a soft, lint-free cloth. Do not use any more "strong" means like ink gum or sandpaper. The point is that the contacts SIM card and in the phone are gilded, which excludes their oxidation. Damage to this thin gold coating will inevitably lead to subsequent deterioration of contacts. Also, you should not, and try to make great efforts to SIM card, trying to press it more tightly to the contacts, because in the end you can damage it, because, in fact, it is a frameless microcircuit on a plastic or ceramic substrate. If there are indeed doubts about the contact density, then a quite satisfactory result can sometimes be obtained simply by a small piece of paper folded several times and placed on top so that it presses it when the battery is connected.
If all the described actions did not work, then it remains to try to check the operation of the phone with another SIM card, and this card with another phone. Perhaps in this way it will be possible to identify the "guilty".
However, cases of "incompatibility" of some types are also known. SIM cards with certain phone models. At the same time, in other combinations, both cards and phones work fine. The reason for this may be some (acceptable by the standard!) scatter of signal parameters that are exchanged between the phone and the card in the process of joint work. Such an effect can manifest itself, for example, only under certain conditions: as the battery is discharged, in heat or frost, etc. Another reason for this problem may be a mismatch in operating voltages. All early versions SIM cards were designed for an operating voltage (from the phone) of 5.5 V, and modern cards usually work with a voltage of 3.3 V. A mismatch in operating voltages does not lead to the failure of the phone or card, but may be the reason for their unsatisfactory interaction.
From an organizational and legal point of view, the most successful solution to this technical problem is possible only if the phone was purchased together with SIM card. In this case, we can talk about the inoperability of the kit. In other cases, the task is more difficult, since each of the devices, in principle, works. The only way out here can only be to check the phone right in the process of purchasing it with the card with which it is planned to be used.
Technically, this protection method is implemented in software and can be implemented in various ways, but its essence is as follows. The operator orders a batch of phones from the manufacturer, on which a special version of software is installed during the manufacturing process, containing protection based on a unique set of operator codes (NCC) and country of location of the network (MCC). Since the same codes contain SIM card, then each time the phone is turned on, it checks these codes. If they match, then the phone is working normally, if not, a corresponding inscription appears on the screen.
If necessary, this type of protection can be removed by entering special unlock codes directly from the telephone keypad. SIM-lock, usually supplied by the manufacturer along with a batch of phones. Another way to disable the lock (since no hardware changes were made to the phone to enter it) is to replace the software. The operation is not very complicated and may well be performed by artisanal methods. Strictly speaking, if the newly installed information from it is available only to the internal processor and cannot be read from outside in any way. Thanks to such measures, "hacking" is possible only by direct selection of the necessary numbers, which is achievable only in cases where the card falls into the hands of intruders for a long time. But even against such actions, all new cards have special protection based on limiting the total number of allowed accesses to the card, after reaching which it is blocked and stops working. This number is set large enough so that it does not show up during normal phone use during the entire real-time "life" of these products. However, the established limit is significantly less than the number of hits that are usually required to select numbers when a card is hacked. In other words, SIM card quite reliably protects the subscriber from various attempts of illegal use of communications at his expense.
However, the resourcefulness of attackers knows no limits, and a rather original method of quick hacking SIM cards was also found. Very briefly, its essence lies in the fact that when referring to SIM card the activity of the internal processor, and, consequently, the current consumed by it through the corresponding contacts of the card from an external power source, turn out to be different in cases where the specified code does not completely correspond to the required one or partially coincides with it. Thus, by controlling the current drawn SIM card in the course of work, it can be hacked by the method of selecting numbers much faster.
In other words, general advice to all owners SIM cards there can only be a recommendation not to give them to strangers, for example, together with the phone during its repair, maintenance or for temporary use. This advice should probably be considered fair for other types of smart cards with a processor - banking, access control, etc.
Initially, they were produced in a "large" format - in the size of a standard plastic card. This was done in order to ensure the possibility of universal use. SIM cards, both in cell phones and in ordinary fixed payphones, which was implemented in some European countries. However, life has shown the inexpediency of such universality. SIM cards). And this is not surprising - the idea of allocating all personal settings and subscriber data from a cell phone to a separate plug-in card with a microcomputer has already confidently proved its expediency. Most likely, universal cards, like modern SIM cards, in the future will become the property of a variety of mobile communication devices, and not only.
Igor Skolotnev