  Security is a primary concern for the networks aiming at the utilization of
Cellular (C) services for connecting Vehicles to Everything (V2X). At present,
C-V2X is observing a paradigm shift from Long Term Evolution (LTE) - Evolved
Universal Terrestrial Radio Access Network (E-UTRAN) to Fifth Generation (5G)
based functional architecture. However, security and credential management are
still concerns to be resolved under 5G-V2X. A sizably voluminous number of key
updates and non-availability of sub-functions at the edge cause adscititious
overheads and decrement the performance while alarming the possibilities of
variants of cyber attacks. In this paper, security management is studied as a
principle of sustainability and its tradeoff is evaluated with the number of
key-updates required to maintain an authenticated connection of a vehicle to
the 5G-terminals keeping intact the security functions at the backhaul. A
numerical study is presented to determine the claims and understand the
proposed tradeoff.
