Question: In Iu mode, which algorithm is utilized for the Data Integrity procedure between the Mobile Station (MS) and the Radio Access Network (RAN), and what is its key input?
Option 1: AES Algorithm with Authentication Key (AK) as input
Option 2: UMTS Integrity Algorithm (UIA) with Ciphering Key (CK) as input
Option 3: UMTS Integrity Algorithm (UIA) with UMTS Integrity Key (IK) as input
Option 4: SHA-256 Algorithm with Anonymity Key (AN) as input
Explanation: The correct answer is Option 3 because, in Iu mode, the Data Integrity procedure employs the UMTS Integrity Algorithm (UIA), with the key input being the UMTS Integrity Key (IK), ensuring integrity of radio signalling between the MS and the RAN.