Question: In a Generic Bootstrapping Architecture (GBA) scenario, what is a crucial aspect for a Network Application Function (NAF) to consider when utilizing shared key material established between a UE and a BSF, especially in the context of GBA_U?
Option 1: Ensuring the shared key material is stored indefinitely for future application runs.
Option 2: Relying solely on local policy for key selection without considering external indications.
Option 3: Focusing exclusively on the lifetime of the shared key material, ignoring its local validity conditions.
Option 4: Taking additional measures to guarantee key freshness, as GBA itself does not ensure it.
Explanation: This is correct because GBA does not guarantee the freshness of the key (e.g., Ks_ext_NAF or Ks_int_NAF) without additional measures. Ensuring key freshness is crucial for preventing replay attacks, especially in protocols lacking replay protection over unconnected runs, requiring thoughtful consideration and action from both the UE and the NAF to understand GBA's limitations and the importance of security in telecom networks.