SIM Cards

Why in News?

In contemporary times, Smartphone usage has significantly outpaced other electronic devices, necessitating a proper description of Subscriber Identification Module (SIM) Cards, an essential component of smartphones.

About SIM Card

1. Definition: A SIM card is a microchip that identifies subscribers on a cellular network, serving as an individual's ID card within the network's vast city.
2. International mobile subscriber identity (IMSI): The ID card contains an IMSI, a unique number used to confirm the identity of the subscriber when others attempt to contact them on the network.
3. Role in Network Access: A SIM card is required to connect a mobile phone to a GSM-based cellular network. The connection is secured using a unique authentication key (SAK), which functions as both a digital lock and key mechanism.

• SIM cards store SAK, which is inaccessible through phones. When a phone communicates with the network, it signs signals using this key, verifying connection legitimacy.
• Duplicating a SIM card is possible by accessing and copying the authentication key onto multiple cards.

4. Information Storage:

• A SIM card is not only used for network access but also functions as a storage unit for various types of data. The device stores not only the IMSI but also the integrated circuit card identifier, the subscriber's location area identity, and a list of preferred roaming networks.
• SIM cards can store emergency contact numbers, contacts, and SMS messages, provided they have sufficient space.
• This compact chip is crucial for the functionality and security of mobile communication on GSM-based networks.

How Does a SIM Card Work?

1. Standard of SIM Card: SIM cards are compliant with the ISO/IEC 7816 international standard, which is managed by the International Organization for Standardization and the International Electrotechnical Commission.
2. Pin Functions and Standards: The ISO/IEC 7816-2 standard defines the roles of pins on a SIM card, which are segmented into metal contacts for specific purposes.

• The SIM card has 15 pins, each indicating different functions.

3. SIM Card's Network Role: The phone sends data through the network when a subscriber calls a recipient's number, authenticated by the SIM card key.

• The data is sent to a telephone exchange, where the recipient's identity is confirmed and a call is directed to them.

How have SIM cards changed?

1. Evolution of Smart Cards: Smart cards, including SIM cards, have been in existence since the late 1960s, evolving significantly due to Moore's law-driven technological advancements.

• Moore's law states that the number of transistors in an integrated circuit (IC) doubles every two years, resulting in faster and cheaper computers over time.

2. SIM Card Standards and Development: The European Telecommunications Standards Institute (ETSI) played a crucial role in developing the GSM Technical Specification for SIM cards.

• The study analyzed various physical features such as operating temperature and contact pressure, as well as authentication and data access characteristics.

3. Transition and Compatibility: The term 'SIM card' initially encompassed both hardware and software until 2G networks, but with the advent of the Universal Mobile Telecommunications System and 3G networks, it changed.

• The term 'SIM' was used to refer to the software, while the hardware was referred to as the Universal Integrated Circuit Card (UICC).

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