Question: What is required for a user to gain access to the USIM, ensuring that only authorized users can access it?
Option 1: The user must have physical possession of the USIM.
Option 2: The user and USIM must share a secret, such as a PIN, stored securely in the USIM.
Option 3: The user must be connected to a specific network or operator.
Option 4: The user must have a specific type of device or software.
Explanation: This is because the shared secret (e.g. PIN) serves as a means for the USIM to authenticate the user, ensuring that access is restricted to authorized users only.