Secure multi-server coded caching

This paper considers multiple cache-enabled end-users connected to multiple servers through a linear network. We also prevent an external eavesdropper from obtaining any information about the original files in cache- aided networks. The eavesdropper does not exist in the placement phase. He can analyze and capture the multi-cast messages in the content delivery phase. He receives a single linear combination derived from each multi-cast message. Hence, we only consider the security of the delivery phase. Our work generalizes the secure caching problem with one server to a multi-server setup. A secure centralized multi-server coded caching scenario is considered, and closed-form coding delay and secret shared key storage expression are provided. Regarding our security guarantee, we show that the delivery phase does not reveal any information to the eavesdropper in terms of the mutual information metric. We analyze the system's performance in terms of coding delay and guarantee the security of our scheme using the mutual information metric. Numerical evaluations verify that security incurs a negligible cost in terms of memory usage when the number of files and users increases, i.e., the secure and insecure bounds almost coincide. Also, we numerically show that our proposed scheme outperforms the secure coded caching problem with one server.