Question: In a USIM supporting MBMS security context, what happens if no EFMSK record is found matching the received Key Domain ID and Key Group part of the MSK ID?
Option 1: The USIM generates a new MSK with the provided Key Domain ID and Key Group part.
Option 2: The USIM updates all existing MSKs to match the new Key Domain ID and Key Group part.
Option 3: The USIM ignores the request and continues with existing security settings.
Option 4: The USIM abandons the function, returns a 'not found' status, and takes no further action on MSKs.
Explanation: If the USIM cannot identify a matching record in EFMSK based on the provided Key Domain ID and Key Group part of the MSK ID, it terminates the process, indicating that the referenced data was not found. This ensures integrity and prevents unintended alterations to existing security configurations.