Coded Caching with Demand Privacy: Constructions for Lower Subpacketization and Generalizations

Coded caching is a technique where we utilize multi-casting opportunities to reduce rate in cached networks. One limitation of coded caching schemes is that they reveal the demands of all users to their peers. In this work, we consider coded caching schemes that assure privacy for user demands. We focus on reducing subpacketization in such schemes. For the 2-user, 2-file case, we propose a new linear demand-private scheme with the lowest possible subpacketization. This is done by presenting the scheme explicitly and proving impossibility results under lower subpacketization. We then propose new construction schemes for placement delivery arrays. This includes direct as well as lifting constructions. Coded caching schemes based on these can achieve lower subpacketization. A new notion of privacy with security is introduced which combines demand privacy and content security and schemes to achieve the same are proposed. Additionally, when only partial privacy is required, we show that subpacketization can be significantly reduced when there are a large number of files.

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