  In a secure coded caching system, a central server balances the traffic flow
between peak and off-peak periods by distributing some public data to the
users' caches in advance. Meanwhile, these data are securely protected against
the possible colluding users, who might share their cache. We model the system
as a flow network and study its capacity region via a network
information-theoretic approach. Due to the difficulty of characterizing the
capacity region straightforwardly, our approach is two folded from the
perspective of network information theory. On one hand, we identify the inner
bound of capacity region by proposing a coded caching scheme to achieve a low
load secure data transmission. On the other hand, we also establish outer outer
bounds on the capacity region, which show that our proposed scheme is order
optimal in general under specific circumstance.
