Question: In a Generic Bootstrapping Architecture (GBA), how does a Bootstrapping Server Function (BSF) restrict the applicability of key material to a specific Network Application Function (NAF)?
Option 1: By using a unique key derivation procedure for each NAF
Option 2: Through explicit configuration of allowed NAFs on the BSF for each key generation
Option 3: By employing a separate authentication protocol for each NAF
Option 4: Via periodic key refreshes to limit key material exposure
Explanation: The correct answer is Option 1 because the BSF uses a key derivation procedure to restrict the applicability of the key material to a specific NAF, generating unique session keys for each NAF and ensuring secure, isolated communication between the UE and multiple NAFs.