Question: In a 3GPP System Architecture Evolution (SAE) scenario, when a Master eNodeB (MeNB) initiates an S-KeNB update procedure, what action does the MeNB take regarding the SCG Counter after computing a fresh S-KeNB?
Option 1: The MeNB resets the SCG Counter to its initial value.
Option 2: The MeNB keeps the SCG Counter unchanged for backward compatibility.
Option 3: The MeNB increments the SCG Counter, as defined in the security architecture specifications.
Option 4: The MeNB decrements the SCG Counter to avoid key exhaustion.
Explanation: Incrementing the SCG Counter upon computing a fresh S-KeNB is crucial for maintaining the security and integrity of the communication between the Master eNodeB (MeNB), Secondary eNodeB (SeNB), and User Equipment (UE). This action ensures that each new S-KeNB derivation is uniquely identified, preventing replay attacks and ensuring the freshness of the derived keys (KUPenc and KUPint) used for encryption and integrity protection.