Question: What happens during an SRVCC handover of a PDN connection for emergency bearer services when transitioning from Iu mode to A/Gb mode without integrity protection?
Option 1: The MS and network derive new keys using existing security context.
Option 2: The MS and network perform key exchange to establish new security parameters.
Option 3: The MS and network skip key derivation but re-authenticate the user.
Option 4: The MS and network do not perform key derivation or any additional security procedures.
Explanation: According to the specification, when an SRVCC handover occurs for emergency bearer services without integrity protection while transitioning from Iu mode to A/Gb mode, neither the Mobile Station (MS) nor the network performs key derivation. This is a specific scenario where the existing security context remains valid, and no additional security procedures are required.