FAQ’s About SIM Cards and SIM Related Technology

28 min readJun 21, 2021

The mobile/Cell phone is the one of the most important gadgets in our life. It is how we communicate, chat with our friends and family across the world, share information, share news, share fun, make payments, tap for our transportation, etc. It is the reason we remember every single person’s anniversary. It’s also a portable camera and videoe recorder. It can also be a handy replacement for a printed-out ticket or debit/credit card, key to open your doors, or start your car, etc, the list is endless. But have you ever thought that it’s actually the SIM card hiding inside that phone that makes all the convenience possible? That tiny chip inside your phone is a total game-changer.

Do you know, what a SIM card is or how it works?

What is a SIM Card?

A SIM card, otherwise known as a Subscriber Identity Module, is a small piece of plastic with a chip and memory that slots into your mobile phone to allow you to communicate with your mobile phone carrier/provider. In other terms, a SIM card is the middle point which connects your phone and network provider together. This allows you to make calls, send SMS messages and connect to mobile internet services (such as 3G, 4G, 5G, etc.). As well as containing a mixture of information, they hold a unique ID, known as the International Mobile Subscriber Identity(IMSI), which identifies your phone to the network. For example, the IMSI is used to connect another user that is phoning your mobile number to your specific phone, rather than to someone else’s.

SIM card technology is one of the most popular technology which is used in Mobile phones to activate the connection and to communicate and for making links with the server system and also used in various electrical and electronics projects like payments. It is the Subscriber Identity Module that contains the integrated circuit to store the International Mobile Subscriber Identity or IMSI and the keys to identify and authenticate the subscribers on the communication system.

A SIM card is a small smart card made up of embedded contacts and semiconductors that has gone through four sizes over the years:

Full-Size (1FF or 1st Form Factor) was the size of a credit card; 85.6 mm x 53.98 mm.
Mini-SIM (2FF) was drastically smaller coming in at 25 mm x 15 mm first being used in 1996.
Micro-SIM (3FF) made improvements in length with measurements of 15 mm x 12 mm.
Nano-SIM (4FF) is the most recent form and is 12.3 mm x 8.8 mm.

SIM cards are effectively mini circuit boards which identify your service provider and your mobile phone number.

Intro

Historically SIM/Smart card development has mainly been done directly by commercial companies (operators, smart card manufacturers and specialised vendors) using proprietary hardware and software solutions. With the introduction of the Java Card standard this field of software development has finally been opened up to the general developer audience. New interesting applications and services for smart cards are now being developed by a broad range of companies whose solutions benefit from the security, integrity and robustness provided by a smart card. A well-known fact is that domain knowledge is the key factor that determines a projects’ success or failure. However, in this field the necessary knowledge is not so easy to obtain unless you are or have been part of the SIM/Smartcard technology fraternity.

Brief History of the SIM

The first ever SIM card was made in 1991 by Giesecke & Devrient GmbH, a German-based smart card maker/manufacturer and personalisation company. The company sold the first 300 SIM cards to the Finnish wireless network operator, Radiolinja. In 1992, they sold the first GSM mobile phone with a SIM card; it was a Nokia 1101. Today, it’s hard to find a person who’s never used a SIM card maybe in the very remote rural parts of the world. Over 7 billion gadgets around the world use the SIM cards to make calls, send SMS and surf the web. Experts predict this number is going to grow to 20 billion in the near future.

At the time of the SIM creation, Europe had adopted GSM (Global System for Mobile Communication) regulations. GSM is a digital mobile network that is used widely by mobile phone users in Europe and across the globe. Adopting GSM permitted users to connect to their chosen mobile network and make phone calls to users on other networks. Effectively, it was a turning point for mobile phones.

Now, the use of SIM cards allows a staggering seven billion devices to connect to mobile networks, globally

The European Telecommunications Standards Institute (ETSI) holds most of the SIM patents, but other Telcos also have some important patents thanks to which SIMs work. The largest manufacturer of SIM cards in the world is Gemalto, with headquarters in Amsterdam and about 15,000 employees.

To make calls, send text messages, or use mobile data, you will need to insert a SIM card in the phone in order to connect to your mobile network. The tiny piece of plastic slotted into the side of your device is crammed full with information that allows you to communicate with one another.

A SIM card is also a Smart Card

What are the different SIM formats?

There are three main SIM formats which are currently used within mobile phones. These are a Standard, Micro, and a Nano SIM.

Listed below are the sizes for each SIM format:

Standard SIM: 85mm x 53mm
Micro SIM: 15mm x 12mm
Nano SIM: 12.3mm x 8.8mm

In addition to the three main SIM card sizes, is the embedded SIM, or better known as the eSIM. Essentially, the eSIM is a reprogrammable chip that is integrated into the structure of the cellular device. It acts as a ‘universal’ SIM card which remains inside the device, whilst the information it holds can be updated or changed without the removal of the card. The eSIM is much smaller than the standard Nano SIM cards and is currently compatible with phones such as the Apple iPhone XS and Google Pixel 3.

Embedded SIM (eSIM) size: 6mm x 5mm

Regardless of the different dimensions or the type of mobile phone you are using, all SIM cards hold the same kind of information within the small chip.

The ‘Profile’

A Profile comprises of the telecom operator data related to a subscription, including the operator’s credentials and potentially operator or third-party SIM based applications. The secure element in the eSIM solution is called the eUICC, this can accommodate multiple Profiles. Profiles are remotely downloaded over-the-air into a eUICC. Although the eUICC is an integral part of the device, the Profile remains the property of the operator as it contains items “owned” by the operator (IMSI, ICCID, security algorithms, etc.) and is supplied under licence. The content and structure for interoperable Profiles stored on eUICCs are similar to those installed on traditional SIMs. The interoperable description of these Profiles is defined by the SIMAlliance. [Credit: GSMA]

How does a SIM card work?

A SIM card serves as your phone’s credentials to access the carrier network. Because the SIM holds this information, you’re able to pop it into any phone with the same carrier, or an unlocked phone, to access the network.

How it works:

When you boot up your mobile phone, it obtains the IMSI from the SIM, and then relays the IMSI to the network in order to request access.
The operator network searches the database for your IMSI and the associated Ki.
Assuming your IMSI and Ki are verified, the operator then generates a random number, signs it with your Ki using the GSM cryptography algorithm for computing SRES_2, and creates a new unique number.
The network then sends that unique number back to the device, which then passes it to the SIM to use in the same algorithm, creating a third number. This number is then relayed back to the network.
If both numbers match, the SIM card is deemed legitimate and is granted access to the network.

So if you break the screen on your phone, while it’s being fixed, you can take your SIM card out and put it in a replacement phone and still access phone calls, texts, and data from your network.

What size SIM card do I need for my device?

If you are unsure what size SIM card you need for your device, take a look at the user manual that came with the phone or the manufacturer website which will give you information on what size/format SIM you require.

Can someone track my location with the help of a SIM card?

This is a question for both privacy and security. While it is creepy to think someone can track your physical location for their purposes, it’s good to know your phone can be found when it’s lost or stolen. It can also be helpful when it concerns lost kids or elderly people, for example.

So, a SIM card can help to establish your location. When you insert a SIM in your mobile phone, tablet, or even car, and turn the device on, it starts connecting to telecommunication cell towers to catch a signal. As you move around, your SIM works with the towers nearest to you to provide the strongest signal. All these towers have known physical locations. When phone companies or the police use their algorithms to find out how strong the signal is from the different towers, they can narrow down the search area significantly.

Services like “Find my phone” also use Wi-Fi data to know a more specific location. Of course, it’ll only work when the Wi-Fi on your gadget is on. Add GPS information to this, and you will get fairly accurate data on any gadget’s whereabouts in real time. GPS will only be handy in this situation when you have cellular data enabled on your plan or gadget. So if you want complete privacy, turn it off, along with Wi-Fi, and tracking you down using information from your SIM alone maybe a challenge though not impossible.

Can SIM cards break?

SIM cards, like just about anything on this planet, can get damaged or broken and don’t last forever. You’ll be the first to know when that happens, as your phone will inform you the chip is defective. You will not be able to connect to your telecom/cellular provider in this case. Water is unlikely to be the reason for that damage, though, since basically all new phones have sealed ports and jacks. The SIMs themselves have always been waterproof.

Why are SIM cards getting smaller?

The first SIM cards were around the same shape and size of a credit card. They worked fine with the first mobile phones, but as mobile technology evolved and phones got smaller, the SIM cards clearly needed improvement, too. Imagine fitting a credit card into an iPhone — not the best idea, right? So fortunately, SIMs over time, became smaller and more powerful.

First came the standard thumbnail-sized SIMs. They were standard until 2010, when the Micro-SIM became universal. But even that SIM still had too much useless plastic.

In 2012, Nano-SIMs came into play, which are in essence just little chips with no extra plastic around them. If you ever need to insert a newer generation SIM in an older phone, there are special adaptors for that.

The current SIM is an “eSIM”s, which means embedded SIM card. Its size is just a fraction of a Nano-SIM. Forget the huge pieces of plastic and scissors you used to cut out the chips! In fact, there’ll be no physical SIM cards — instead, there will be tiny chips on your phone’s logic board.

The information on the chip will be rewritable, so you will be able to change your carrier with a few easy steps. eSIMs will be cloud-based, super secure, super fast and convenient to use. It will also be a win-win situation for the manufacturers/vendors/personalization bureaus; less distribution costs, and better design with more free physical space on your gadget! Losing one slot on your phone is also great because it will ensure extra protection from water and dust getting inside.

GSM (Global System for Mobile Communications) — still the most common worldwide mobile phone standard. It uses full digital signaling in respect to its predecessors which used a mix of analogue and digital signaling. GSM is considered to be a second generation (2G) mobile communications standard.

GSM Association (GSMA) — a big group of phone operators and related companies. GSMA aims to spread GSM related technologies throughout the world. It was the GSM standard that pioneered the concept of using smart cards in cellular mobile phones.

What is the Composition of the network

The GSM network has four separate parts that work together to function as a whole: the mobile device itself, the Base Station Subsystem (BSS), the Network Switching Subsystem (NSS) and the Operation and Support Subsystem (OSS).

The mobile device connects to the network via hardware. The subscriber identity module (SIM) card provides the network with identifying information about the mobile user.

What is the Purpose of a SIM Card?

A SIM contains a globally unique serial number (called an international mobile subscriber identity aka IMSI ) that your cell provider can match to your contract and then allow the appropriate level of service (i.e. voice, 3G data or 4G data or no data, texting or no texting…).

Will My Phone Work Without a SIM Card?

Partially. The phone, text and cellular data functions on your cell phone require a SIM card because you need a SIM to connected to a cellular provider (like O2, Vodafone, EE, Verizon, Telus, Bell, Orange…). However, nearly all other functions like (streaming Netflix or just surfing via WiFi, camera, calculator and flashlight apps, …) will operate fine without a SIM.

Can I Move My SIM Card To A Different Mobile Phone?

Yes you can. If the Mobile/cellphone is “unlocked”, you will have no problem getting your SIM working in a new device. If your current SIM card is too large, you can cut it down to size. If your current SIM is too small you can purchase a SIM expander otherwise known as an adaptor.

What Data is stored on a SIM card?

SIM cards contain a globally unique serial number, your cellular number, the company that provides you with cellular service (like EE, Vodafone, O2, Orange, Verizon, Telus, Bell, etc) and sometimes your address book (i.e. contacts) stored on the phone (i.e. NOT contacts you have stored with your email like Outlook or Office 365).

Below is a list of part of what else the SIM stores:

Integrated Circuit Card Identifier (ICCID) — It is the Primary account number that has 19 digits long. The number has sections like Issuer Identification Number (IIN), Individual Account Identification, Check digit etc.

Abbreviated Dialing Numbers (ADN) — Any number and name dialed by the subscriber are saved by the ADN EF. The type of number and numbering plan identification is also maintained under this. This function works on the subscriber’s commonly dialed numbers. The ADN cannot be changed by the service provider and they can be attributed to the user of the phone. Most SIMs provide 100 slots for ADN entries.

Fixed Dialing Numbers (FDN) — The FDN EF works similar to the ADN because it involves contact numbers and names. With this function, The user doesn’t have to dial numbers; by pressing any number pad of the phone, he can access the contact number.

The Last Number Dialed (LND) — The LND EF contains the number most recently dialed by the subscriber. The number and name associated with that number are stored in this entry. Depending upon the phone, it is also conceivable that the information may be stored in the handset and not on the SIM. Any numbers that may be present can provide valuable information to an investigator.

Messaging Information — Messaging is a communication medium by which text is entered on one cell phone and delivered via the mobile phone network. The short message service contains texts and associated parameters for the message. SMS entries contain other information besides the text itself, such as the time an incoming message was sent, as recorded by the mobile phone network, the sender’s phone number, the SMS center address, and the status of the entry.

Advice of Charge — Governs payments and receipts of your services.

OTA(Over the Air) — This is the process of downloading and upgrading of SIM applications (Applets). These are typically pushed out by the operator who wants all of their customers to have access to certain applications (like Value Added Services) available on their phones. End customers can be allowed to request downloading of additional applications (like games and news)

Great care has to be taken here to see that the customer really has enough space for this on the card. Actual distribution of applications was traditionally done through multiple SMS messages but today it is done over TCP/IP (GPRS/3G, etc.

NFC(Near Field Communication) — These wireless communications technologies are mainly used for credit-card-on-a phone solutions today. However, it can also be used for peer-to-peer communications and or as Machine2Machine. NFC can for example be used as a simple way to download new applications to the phone (and/or SIM card) or to provide various financial services

Mobile Country Code(MCC) — Identifies the country of origin by a two- or three-digit code

Mobile Subscriber Identification Number(MSIN) — Ten-digit code that is the link between you and your cellular carrier.

Mobile Station International Subscriber Directory Number(MSISDN) — is a number uniquely identifying a subscription in a Global System for Mobile communications or a Universal Mobile Telecommunications System mobile network. It is the mapping of the telephone number to the subscriber identity module in a mobile/cellular phone. This number includes a country code and a National Destination Code which identifies the subscriber’s operator.

International mobile subscriber identity (IMSI)

SIM cards are identified on their individual operator networks by a unique International Mobile Subscriber Identity (IMSI). Mobile Network operators connect mobile phone calls and communicate with their market SIM cards using their IMSIs.

The format is:

The first three digits represent the Mobile Country Code (MCC).
The next two or three digits represent the Mobile Network Code (MNC). Three-digit MNC codes are allowed by E.212 but are mainly used in the United States and Canada.
The next digits represent the mobile subscriber identification number (MSIN). Normally there are 10 digits, but can be fewer in the case of a 3-digit MNC or if national regulations indicate that the total length of the IMSI should be less than 15 digits.
Digits are different from country to country.

MSISDN is built up as;

MSISDN = CC+ NDC + SN

CC = Country Code — The country code identifies a country or geographical area, and may be between 1–3 digits.

NDC = National Destination Code

SN= Subscriber Number

In general terms it is simply the phone number that relates to the SIM card in a mobile device. Each SIM card has a code known as an IMSI (International Mobile Subscriber Identity) which uniquely identifies the SIM card itself. The MSISDN identifies the network to which that SIM card is subscribed, whilst the IMSI is fixed for the life of the SIM the MSISDN can change as different networks are subscribed to.

A SIM has a unique IMSI(serial number) that does not change, while the MSISDN(phone number)can change in time, i.e. different MSISDNs can be associated with the SIM.

What is the Difference Between the IMSI and MSISDN?

An IMSI is a number that identifies a mobile phone plan subscriber. It’s usually stored on a SIM card. If a phone has multiple SIM cards, each card has its own IMSI. If you move a SIM card to a new phone, the IMSI moves with the card and doesn’t stay with the phone.

An MSISDN is simply the full phone number of a mobile phone, including the country code and any area code or similar code issued by that country. Unlike an IMSI, which is bound to a particular SIM card, MSISDNs can be transferred from phone to phone, SIM to SIM.

Local Area Identity(LAI) — The Location Area Identity uniquely identifies a Location Area (LA) within a mobile network. It consists of the Mobile Country Code (MCC), the Mobile Network Code (MNC) and the Location Area Code (LAC). The LAI is used to keep track of the mobile subscribers in the network.

Personal Identification Number(PIN) — The code you use to lock and unlock the phone.

Service Dialing Number(SDN) — This information can be used to contact the service provider to obtain even more information than is stored on the SIM card.

Issuer Identification Number (IIN)

Maximum of seven digits:

Major industry identifier (MII), 2 fixed digits, 89 for telecommunication purposes.
Country code, 2 or 3 digits, as defined by ITU-T recommendation E.164.
NANP countries, apart from Canada, use 01, i.e. prepending a zero to their common calling code +1
Canada uses 302
Russia uses 701, i.e. appending 01 to its calling code +7
kazakhastan uses 997, even though it shares the calling code +7 with Russia
Issuer identifier, 1–4 digits.
Often identical to the Mobile Network Code (MNC).

Individual Account Identification

Individual account identification number. Its length is variable, but every number under one IIN has the same length.
Often identical to the Mobile Subscription identification Number (MSIN).

Check digit

Single digit calculated from the other digits using the Luhn algorithm.

With the GSM Phase 1 specification using 10 octets into which ICCID is stored as packed BCD, the data field has room for 20 digits with hexadecimal digit “F” being used as filler when necessary.

In practice, this means that on GSM SIM cards there are 20-digit (19+1) and 19-digit (18+1) ICCIDs in use, depending upon the issuer. However, a single issuer always uses the same size for its ICCIDs.

To confuse matters more, SIM factories/personalization companies, seem to have varying ways of delivering electronic copies of SIM personalization datasets. Some datasets are without the ICCID checksum digit, others are with the digit.

Authentication key (Ki)

The Ki is a 128-bit value used in authenticating the SIMs on a GSM mobile network (for USIM network, you still need Ki but other parameters are also needed). Each SIM holds a unique Ki assigned to it by the operator during the personalization process. The Ki is also stored in a database (termed authentication centre or AuC) on the carrier’s network.

The SIM card is designed to prevent someone from getting the Ki by using the smart-card interface. Instead, the SIM card provides a function, Run GSM Algorithm, that the phone uses to pass data to the SIM card to be signed with the Ki. This, by design, makes using the SIM card mandatory unless the Ki can be extracted from the SIM card, or the carrier is willing to reveal the Ki. In practice, the GSM cryptographic algorithm for computing SRES_2 (see step 4, below) from the Ki has certain vulnerabilities that can allow the extraction of the Ki from a SIM card and the making of a duplicate SIM card.

Authentication process:

When the mobile equipment starts up, it obtains the international mobile subscriber identity (IMSI) from the SIM card, and passes this to the mobile operator, requesting access and authentication. The mobile equipment may have to pass a PIN to the SIM card before the SIM card reveals this information.
The operator network searches its database for the incoming IMSI and its associated Ki.
The operator network then generates a random number (RAND, which is a nonce) and signs it with the Ki associated with the IMSI (and stored on the SIM card), computing another number, that is split into the Signed Response 1 (SRES_1, 32 bits) and the encryption key Kc (64 bits).
The operator network then sends the RAND to the mobile equipment, which passes it to the SIM card. The SIM card signs it with its Ki, producing SRES_2 and Kc, which it gives to the mobile equipment. The mobile equipment passes SRES_2 on to the operator network.
The operator network then compares its computed SRES_1 with the computed SRES_2 that the mobile equipment returned. If the two numbers match, the SIM is authenticated and the mobile equipment is granted access to the operator’s network. Kc is used to encrypt all further communications between the mobile equipment and the network.

Location Area Identity(LAI)

The SIM stores network state information, which is received from the Location Area Identity (LAI). Operator networks are divided into Location Areas, each having a unique LAI number. When the device changes locations, it stores the new LAI to the SIM and sends it back to the operator network with its new location. If the device is power cycled, it takes data off the SIM, and searches for the prior LAI.

USIM

In GSM-only times, the SIM consisted of the hardware and the software. With the advent of UMTS this naming was split: the SIM was now an application and hence only software. The hardware part was called UICC. This split was necessary because UMTS introduced a new application, the universal subscriber identity module (USIM). The USIM brought, among other things, security improvements like the mutual authentication and longer encryption keys and an improved address book.

UICC

“SIM cards” in developed countries today are usually UICCs containing at least a SIM application and a USIM application. This configuration is necessary because older GSM only handsets are solely compatible with the SIM application and some UMTS security enhancements rely on the USIM application.

Embedded-SIM (eSIM)

An embedded-SIM (eSIM) is a form of programmable SIM that is embedded directly into a device. The surface mount format provides the same electrical interface as the full size, 2FF and 3FF SIM cards, but is soldered to a circuit board as part of the manufacturing process. In M2M applications where there is no requirement to change the SIM card, this avoids the requirement for a connector, improving reliability and security. An eSIM can be provisioned remotely; end-users can add or remove operators without the need to physically swap a SIM from the device.

Service Provider Name(SPN) — The name of your cellular carrier.

Short Message Service Center(SMSC) — The service center(s) where your text messages are processed.

Unblocking Code(PUK) — If you enter the wrong PIN too many times, the phone locks. The PUK, retrieved from the carrier, unlocks the phone.

Integrated Circuit Card ID(ICCID) — The card’s unique serial number. It is the unique identifier of a Subscriber Identity Module (SIM card) on a mobile device. ICCIDs are stored in the SIM cards and printed on the SIM card body.

Value Added Services(VAS) — Is a popular telecommunications industry term for non-core services, or, in short, all services beyond standard voice calls and fax transmissions. However, it can be used in any service industry, for services available at little or no cost, to promote their primary business.

RAM: A SIM card contains a micro controller. Typical RAM size is between 1 KB and 8 KB,

ROM: This contains the smart cards core operating system and support libraries.

EEPROM/Flash: (also known as E2PROM) stands for electrically erasable programmable read-only memory and is a type of non-volatile memory used in computers, integrated in microcontrollers for smart cards and … Flash memory is a type of EEPROM designed for high speed and high density, at the expense of large erase blocks

Encryption and security: Most cards have custom encryption/signature (hash) verification hardware since the main CPU can be quite slow (especially for code running in a virtual machine). Usually it supports DES /3DES, RC4 but also more recently AES, RSA, DSA, COMP128 and Public Key Infrastructure (PKI) [44]. PKI private keys never leave the card. A hardware random generator is often present to provide more secure encryption key generation. The smart card has to provide protection against tampering

SIM Supplier: Companies that create the physical smart cards from the chips and personalize them to the SIM card format.(e.g. Thales, Idemia, etc), attach additional things like NFC antennas.

Semi-conductor Manufacturer: Designs and creates the chips (e.g. Infineon, Phillips).

Smart Card Issuer: Sets up the card, verifies standards compliance. Defines card hardware specifications. Sometimes they also distribute allowed memory usage and so on (issuing “mounting licenses”) if there are multiple service providers involved

Service Provider: The smart card is managed by a Service Provider. They typically can also revoke the card when needed and can deploy additional applications. Service providers work closely together with the issuers to control the content on the card. Examples of typical service providers are cellular network operators and banks (EMV). Other types of service providers just provide applications but do not control the lifecycle of the card.

Why are there different sizes of SIM Cards?

There are different sizes of SIM cards because mobile device makers (Apple, Samsung, LG, Nokia, Microsoft…) want SIM’s to consume smaller space as the develop thinner and lighter products. The SIM chip that you see on a SIM card is really all that counts. The plastic around that SIM is just to make it easy for your human hands to hold. MicroSIM, Nano SIM… are just a bigger or smaller piece of plastic around the SIM chip.

Can my SIM Card Be Used To Track My Physical Location?

Yes Indirectly. SIM’s allow your mobile phone (or other mobile devices, like some high end tablets and most new cars that eSIMs to connect to a cell tower with a known location. As you physically move the SIM is always negotiating with the wireless towers in the immediate region to connect to the nearest/one with the strongest signal. Telcos and police can use complex algorithms to see how strong your mobile phone signal is to other towers and to narrow down your location.

That cell tower triangulation can be combined with other data to substantially improve accuracy. Some services like Googles FIND MY PHONE and Apples FIND MY iPHONE also use Wi-Fi data (assuming your Wi-Fi is turned on) to further increase the precision of their location services.

This tracking data can be even further enhanced with GPS information. Remember that nearly all mobile phones have GPS receivers but not transmitters. This means if your phone has no access to data (i.e. Wi-Fi is off and you don’t have cellular data enabled on your plan or device) GPS is useless to someone trying to track you.

SIM/Cell Tower, WiFi and GPS combined provide cellular operators and law enforcement with and incredibly accurate and real-time location tracking ability.

Are all SIM cards the same?

No. The circuits within a SIM are different depending on the technology involved. The different “Generations” of cellular networks (aka “G”) may require different hardware inside the tiny SIM card chip.

The SIM Cards come in different versions. All depends on many aspects, like size, use, and range of action.

SIM Card Dimensions:

Standard SIM: 25 x 15 x 0,76 mm.
Micro-sized SIM: 15 x 12 x 0,76 mm.
Nano-sized SIM: 12,3 x 8,8 x 0,67 mm.

What is inside a SIM card chip?

The chip on a SIM card contains a processor, memory and security circuits.

What Is the difference between ‘CDMA’ and ‘GSM’ Technology?

CDMA is the acronym for Code Division Multiple Access and GSM is the acronym for Global System for Mobile communications. Both are radio systems used on mobile phones. Some companies still use CDMA technology. With that system, your device does not use a SIM card. On the contrary, the device has an ESN (electronic serial number) so you cannot change your phone as you wish.

What Data is stored on a SIM card?

SIM cards store network-specific information used to authenticate and identify subscribers on the network. The most important of these are the ICCID, IMSI, Authentication Key(Ki), Local Area Identity (LAI) and Operator-Specific Emergency Number. The SIM also stores other carrier-specific data such as the SMSC (Short Message Service Center) number, Service Provider Name (SPN), Service Dialing Numbers (SDN), Advice-Of-Charge parameters and Value Added Service (VAS) applications. (Refer to GSM 11.11)

Who Is the largest SIM Card manufacturer today?

A global player, a company called Thales which acquired gemalto in 2019, is the largest producer of SIM cards in the world.

How are SIM cards made or personalized individually?

Telecom carriers/operators specify the requirements and or specifications of the SIM and a profile is created by a SIM card personalization vendor. When the profile is approved Data is sent by the telecom carrier to the SIM card vendor/bureau. Data is generated and sent to personalization machines where cards are individually personalized. Personalization of SIM cards is done on machines similar to the one below made by Entrust Datacard. This example is an MPR3800. It is estimated that it can deliver up to 3,400 SIM cards per hour. SIM cards are sent to the telecom carriers plus data for each correspondent SIM card for download to their data bases to enable the activation of the SIM cards.

Picture credit: Datacard

Another company that supplies SIM card personalization machines is called Ruhlamat. Their machines tend to have a higher volumes of cards personalized per minute thus a higher Smart card personalization rate.

Picture credit: Rhulamat GmbH

Who invented the SIM card?

The idea of incorporating an integrated circuit chip onto a plastic card was first introduced by two German engineers in the late 1960s, Helmut Grottrup and Jurgen Dethloff. In February 1967, Gröttrup filed the patent DE1574074 in West Germany for a tamper-proof identification switch based on a semiconductor device. Its primary use was intended to provide individual copy-protected keys for releasing the tapping process at unmanned gas stations

The first SIM card was invented by Munich-based smart card maker Giesecke & Devrient GmbH in 1991, following its development of the ‘SIM plug-in’ in 1989. G&D GmbH sold the first 300 SIM cards to the Finnish wireless network operator Radiolinja.

It was developed at a time when Europe had adopted the GSM (Global System for Mobile Networks) protocols — these allowed users to not only connect to their chosen network, but also to make calls to numbers on other networks. It was the start of the mobile revolution.

What is the Difference between a SIM Card and a Smart Card?

Smart cards integrate well with many types of technology and provide a means to identify and authenticate users and store their data. They are used in ATM cards and building security access cards. Smart cards also can differentiate between mobile communication devices.

Many smart cards include a pattern of metal contacts to electrically connect to the internal chip. Others are contactless, and some are both. Smart cards can provide personal identification. authentication, data storage, and application processing. Applications include identification, financial, mobile phones (SIM), public transit, computer security, schools, and healthcare.

What are the Value Added Services(VAS) on a SIM?

Examples of VAS services implemented on SIM cards: -

Missed calls alerting
Caller number display (display name of caller even if not in your phonebook) Advanced call forwarding.
Multi-line (multiple phone number support on one SIM)
Automatic handset configuration (application configures phone by parsing incoming special SMS).
Account top- up (air time refill)
Transfer of airtime to someone else’s account
Service ordering (games, news and so on). There are a huge number of other operator supplied VAS service types available.

Virtual Sim card — This technology is aimed to create a fully software based SIM card that is executed by the phones operating system, bypassing the need of a physical SIM card and enabling multiple phone numbers for one physical handset. Very high security is demanded if such a virtual SIM is to be possible to move between phones and to avoid data duplication and tampering.

USIM — The Universal Subscriber Identity Module (USIM) application is used in UMTS 3G/4G Networks. It authenticates both the user with the network and network with the user and thus incorporates better authentication mechanisms than GSM (also uses longer keys, better encryption etc.).

CSIM — CSIM are used in CDMA2000 networks and contains similar network parameters as the GSM application found on a SIM card. They used to run on an R-UIM type card but now run on a UICC.

R-UIM cards — These contain all three (GSM+CSIM+USIM) network applications and are usable in all the corresponding networks types. They were first released for use with CDMA2000 networks (the American 3G standard).

TPDU (Transmission protocol data unit) — This is the base smart card standard protocol for sending and receiving data over the serial connection. A modern SIM supports several (four or more) ongoing transactions at one time, these are managed by something called channels

APDU (Application protocol data unit) — APDU is a transactional higher level protocol which piggybacks on-top of TPDU to save space (not following the OSI layered style). The APDU command-set define the SIM/ME interaction. Normally a smart card is a slave unit, here meaning it is the ME that sends commands to the SIM.

eSIM: eSIM is an “electronic or embedded SIM card”, which replaces the physical, plastic SIM card. The eSIM (embedded SIM) is a small chip soldered directly to a board inside a device.

While that’s still technically the definition of an eSIM, it has become more complicated since the eUICC appeared on the IoT landscape. The eUICC is an embedded universal circuit card — the software that allows network operators to send out SIM profiles to their devices remotely. Today, rather than saying “eUICC-capable SIM,” most people simply say “eSIM.”

Ultimately, the eSIM is the hardware component, and the eUICC is the software component or operating system that allows for over the air (OTA) profile updates.

Can I use my phone without a SIM card?

To answer it simply, yes. However, there are limitations when using your phone without a SIM card.

If you only want to use your phone for tasks such as using Wi-Fi, listening to music or taking pictures with, then you don’t need a SIM card fitted. However, if you would like to use your phone as a cellular device then no, it won’t work without a SIM card. To connect to mobile internet services like 4G, receive or make calls, send text messages and even use apps like WhatsApp, you will need to insert a SIM card so you can connect to a mobile network.

Conclusion:

A SIM card is similar to a mini-computer with its operating system, storage, and built-in security features.

The SIM card can add, delete, and manipulate information within its memory, on top of sending and receiving data.

A SIM card can be replaced by users and slides easily into a slot within your phone or mobile device.

Different form factors (FF) co-exist:

The credit-card sized SIM is obsolete
A regular SIM or 2FF measures 15 millimetres by 25 mm
A smaller version of the SIM called the micro-SIM, or 3FF SIM card (Third Form Factor) is 12mm by 15mm
The Nano-SIM or 4FF is 8.8 mm by 12.3 mm
The eSIM or embedded SIM is not removable and comes either plugged-in or soldered. Its size 6mm by 5mm and thickness is 0,67 mm.

With the deployment of 5G networks, which are expected to become the industry standard by 2021, SIM cards are evolving yet again. The GSM Association (GSMA), the organisation that determines specifications for SIM card design and capability, has introduced the Embedded SIM (eSIM) card as an emergent technology for IoT demands of the future.

SIM/Smart Card manufacturing is a high-precision industry and it involves transfer of personal data (from service providers such as banks and telecom companies) to third party product vendors. Data security is important in this business.

The SIM is the final link in the chain between networks and end-users, and no customer can connect to the network without their SIM.

Network operators can communicate, download applications, and manage a SIM card remotely using (OTA) Over-the-Air technology. Network operators can update the SIM cards with new applications and services without requiring users to upgrade their handsets or visit a store location.

With an eSIM, it is your SIM which means you have full control of the profiles and SIM applications. You can put your apps in the eSIM instead of the firmware and your apps have direct access to the authentication and encryption elements on the SIM to strengthen security and to build better solutions for access control plus identity management.