  Vehicular Edge Computing (VEC) is a promising paradigm to enable huge amount
of data and multimedia content to be cached in proximity to vehicles. However,
high mobility of vehicles and dynamic wireless channel condition make it
challenge to design an optimal content caching policy. Further, with much
sensitive personal information, vehicles may be not willing to caching their
contents to an untrusted caching provider. Deep Reinforcement Learning (DRL) is
an emerging technique to solve the problem with high-dimensional and
time-varying features. Permission blockchain is able to establish a secure and
decentralized peer-to-peer transaction environment. In this paper, we integrate
DRL and permissioned blockchain into vehicular networks for intelligent and
secure content caching. We first propose a blockchain empowered distributed
content caching framework where vehicles perform content caching and base
stations maintain the permissioned blockchain. Then, we exploit the advanced
DRL approach to design an optimal content caching scheme with taking mobility
into account. Finally, we propose a new block verifier selection method,
Proof-of-Utility (PoU), to accelerate block verification process. Security
analysis shows that our proposed blockchain empowered content caching can
achieve security and privacy protection. Numerical results based on a real
dataset from Uber indicate that the DRL-inspired content caching scheme
significantly outperforms two benchmark policies.
