What is USIM Universal Subscriber Identity Module

The Universal Subscriber Identity Module (USIM) is an evolution of the traditional SIM (Subscriber Identity Module) card, originally introduced for 2G networks. Let’s dive into the technical details:

1. Functionality:
   • The USIM serves as a smart card used in mobile phones and other mobile devices.
   • Its primary purpose is to securely store subscriber identity information and authentication credentials.
   • Unlike the classic SIM, which is primarily associated with GSM networks, the USIM is used in UMTS (3G) and LTE (4G) devices.
2. Subscriber-Related Information:
   • The USIM stores essential subscriber-related data, including:
     • Subscriber Identity: Unique identification information for the user.
     • Authentication Keys: Used for secure communication between the mobile device and the network.
     • Security Parameters: Necessary for encryption and decryption during communication.
     • Network Access Profiles: Multiple profiles can be stored in a single USIM, each tailored for specific purposes.
3. Security Functions:
   • Authentication: The USIM ensures that the mobile station (device) is genuine and authorized to connect to the network.
   • Ciphering: It provides encryption and decryption services to protect data during transmission.
4. Profile Management:
   • A single USIM can contain multiple profiles.
   • Each profile corresponds to a specific use case or terminal equipment (TE).
   • For example, a multimedia terminal may access additional services not available through a classic terminal using the same subscription.
5. Downloadable and Updatable:
   • Unlike GSM SIM cards, which are typically static, USIMs can be updated over the radio path.
   • This flexibility allows for dynamic changes, such as profile updates or security enhancements.