Demand Private Coded Caching: the Two-File Case

We investigate the demand private coded caching problem, which is an (N,K) coded caching problem with N files, K users, each equipped with a cache of size M, and an additional privacy constraint on user demands. We first present a new virtual-user-based achievable scheme for arbitrary number of users and files. Then, for the case of 2 files and arbitrary number of users, we derive some new converse bounds. As a result, we obtain the exact memory-rate tradeoff of the demand private coded caching problem for 2 files and 3 users. As for the case of 2 files and arbitrary number of users, the exact memory-rate tradeoff is characterized for M∈ [0,2/K] ∪ [2(K-1)/K+1,2].