Components of SIM card, Functioning
- In 2021, there were more than 14 billion cellular devices in the world even though there were only seven billion people.
- The ubiquity of these devices but especially smartphones has come to define the contemporary era together with climate change, antimicrobial resistance, and war.
What is a SIM card?
- ‘SIM’ stands for ‘subscriber identification module’.
- Specifically, it is an integrated circuit, or a microchip, that identifies the subscriber on a given network.
- The SIM card is a subscriber’s ID card in this city.
- In order for a mobile phone to connect to any cellular network that follows the Global System for Mobile Communications (GSM) standard, a SIM card is mandatory.
- This relationship is established using a unique authentication key a piece of data that a user needs to ‘unlock’ access to the network.
- Every SIM card stores this data and it is designed such that the user can’t access it through their phone.
- SIM cards also store information about its own ID number, the IMSI, the subscriber’s location area identity, a list of preferred networks, emergency numbers, and depending on the space available the subscriber’s contacts and SMS messages.
How does a SIM card work?
- SIM cards are designed according to the ISO/IEC 7816 international standard maintained by as its name indicates the International Organisation for Standardisation and the International Electrotechnical Commission.
- It applies to electronic identification cards, including smart cards. In this standard, the card itself consists of the integrated circuit, which is glued to a silicon substrate on the top side.
- On the other side of the substrate are metal contacts, which form the goldcoloured side of the SIM card.
- Wires connect the integrated circuit from its bottom side to the metal contacts on the top side, and the contacts interface with the phone’s data connectors.
- The metal contacts have a segmented appearance.
- Each segment is called a pin and has a specific purpose.
- On the network side, the SIM helps a phone establish its place within a cellular network.
How have SIM cards changed?
- SIM cards are a type of smart card, and the history of smart cards begin in the late 1960s.
- The size and architecture of this microchip evolved in leaps and bounds in the subsequent decades, following Moore’s law.
- The SIM card itself evolved according to the standards that defined the networks to which its users wished to connect.
What is an eSIM?
- Over the years, the SIM card has shrunk from the SIM to the mini SIM to the micro SIM to the nano SIM.
- The latest on this path is the eSIM, with specifications defined by the GSM Association.
- In the eSIM paradigm, the SIM software is loaded on to a UICC that is permanently installed in the mobile equipment in the factory itself, that it can’t be removed.
- An eSIM has two immediate advantages.
- First, it is considered to be environmentally friendlier than a physical SIM: its reprogrammability means no need for more plastic and metal for a new SIM.
- Second, if a malicious person gains access to your phone, they won’t be able to separately access the SIM application nor be able to duplicate it.
- There are also at least two disadvantages.
- First, in some countries, including the U.S., eSIMs can be programmed by subscribers themselves.
- But this process might be difficult for those with low digital literacy, such as the elderly.
- Second, an eSIM can in theory allow network operators to track subscribers’ data, including inside apps on the device, especially in the absence of data privacy laws.