Question: For RRC signalling integrity protection in EPS, which statement about algorithm implementation is correct for both UEs and eNBs?
Option 1: Both must implement 128-EIA1, may implement 128-EIA2, and are not required to implement 128-EIA3.
Option 2: Both shall implement 128-EIA1 and 128-EIA2, and may also implement 128-EIA3.
Option 3: Implementation of all three (128-EIA1, 128-EIA2, 128-EIA3) is optional for both UEs and eNBs.
Option 4: Both are required to implement only 128-EIA3 for RRC signalling integrity protection.
Explanation: For RRC signalling integrity protection in EPS, both UEs and eNBs must implement 128-EIA1 (SNOW 3G based) and 128-EIA2 (AES based), with the option to also implement 128-EIA3 (ZUC based), ensuring a standardized security baseline with adaptability.