In the coded caching problem, as originally formulated by Maddah-Ali and
Niesen, a server communicates via a noiseless broadcast link to multiple users
that have local storage capability. In order for a user to decode the desired
file from the coded multicast transmission, the demands of all the users must
be globally known, which may violate the privacy of the users. To overcome this
privacy problem, Wan and Caire recently proposed several schemes that attain
coded multicasting gain while simultaneously guarantee information theoretic
privacy of the users' demands. In Device-to-Device (D2D) networks, the demand
privacy problem is further exacerbated by the fact that each user is also a
transmitter, which should know the files demanded by the remaining users in
order to form its coded multicast transmissions. This paper solves this
seemingly infeasible problem with the aid of a trusted server. Specifically,
during the delivery phase, the trusted server collects the users' demands and
sends a query to each user, who then broadcasts coded multicast packets
according to this query. The main contribution of this paper is the development
of novel achievable schemes and converse bounds for D2D private caching with a
trusted server, where users may be colluding (i.e., when some users share
cached content and demanded file indices), that are to within a constant factor
of one another.Comment: 64 pages, 6 figures, under review of TIT, parts of results were
presented in ICC 2020 and ISIT 202