Coded Caching with Private Demands

Abstract

Caching is an efficient way to reduce network traffic congestion during peak hours by storing some content at the user’s local cache memory without knowledge of later demands. For the shared-link caching model, Maddah-Ali and Niesen (MAN) proposed a two-phase (placement and delivery phases) coded caching strategy, which is order optimal within a constant factor. However, in the MAN scheme, each user can obtain the information about the demands of other users, i.e., the MAN scheme is inherently prone to tampering and spying the activity/demands of other users. In this paper, we formulate a shared-link caching model with private demands. Our goal is to design a two-phase private caching scheme with minimum load while preserving the privacy of the demands of each user with respect to other users. We propose a private caching scheme by introducing some virtual users, which is order optimal in general except very small memory size regime, but with an extremely high sub-packetization level. By relaxing the information theoretic privacy constraint, we also propose a private caching scheme based on Maximum Distance Separable (MDS) code with the same sub-packetization level as the MAN scheme, which is order optimal for high memory regime.