Secretive Hotplug Coded Caching

In this work, we consider a coded caching model called \textit{hotplug coded caching}, in which some users are offline during the delivery phase. The concept of Hotplug Placement Delivery Arrays (HpPDAs) for hotplug coded caching systems has been introduced in the literature, and two classes of HpPDAs are known. In this paper, we consider a secrecy constraint in hotplug coded caching setup, where users should not learn anything about any file from their cache content, and active users should not gain any information about files other than their demanded file from either their cache content or the server transmissions. We propose two secretive schemes for the two classes of HpPDAs and compare them with a baseline scheme, which is a secretive scheme using PDAs for the classical coded caching setup and can be trivially adapted for the hotplug coded caching setup. We numerically show that our schemes outperform the baseline scheme in certain memory regions.