Question: What is a crucial security aspect that both the Bootstrapping Server Function (BSF) and User Equipment (UE) must support to achieve, as per reference point Ub requirements, but is not mandatory for 2G GBA due to an existing protection mechanism?
Option 1: End-to-end encryption for all bootstrapping transactions
Option 2: Mutual authentication based on a public key infrastructure (PKI)
Option 3: Establishment of shared keys with a predefined lifetime
Option 4: Protection of the permanent user identity (IMPI) using a temporary identity to prevent passive eavesdropping attacks
Explanation: Protecting the permanent user identity (IMPI) against passive eavesdropping attacks by using a temporary identity is a key security requirement for reference point Ub, ensuring user identity privacy. This is particularly important in scenarios where such protection isn't inherently provided, unlike in 2G GBA, where a mandatory TLS tunnel already safeguards the IMPI.