Question: Which of the following security features is ONLY provided by GERAN/UTRAN Security function in Iu mode, and NOT as a standard feature across all modes for user data and signaling?
Option 1: User Identity Confidentiality (temporary identification and ciphering)
Option 2: Authentication of the MS by the Network
Option 3: User Data and Signalling Confidentiality (ciphering)
Option 4: Data Integrity and Origin Authentication of Signalling Data
Explanation: The correct answer is Option 4 because Data Integrity and Origin Authentication of signalling data is specifically highlighted as a security feature provided only in Iu mode, distinguishing it from the other options which are either generally applicable or have additional specific conditions not limited to Iu mode.