  Coded caching, introduced by Maddah-Ali and Niesen (MAN), is a model where a
server broadcasts multicast packets to users with a local cache that is
leveraged so as to reduce the peak network communication load. The original MAN
model does not consider missing demands (i.e., some users may not request a
file) or privacy issues (i.e., decoding the multicast packets may expose the
users' demands). The former issue was captured by the hotplug model with
offline users, where the server starts sending multicast packets after having
received a certain number of file requests. The latter issue was addressed by
devoting part of the cache to store privacy keys to help users decode their
requested file while remaining completely ignorant about the demands of the
remaining users. This paper investigates the problem of private demands against
colluding users in the hotplug model with offline users. Two achievable schemes
are proposed based on Maximum Distance Separable (MDS) codes. They achieve
lower subpacketization, and lower load in the small memory regime compared to
baseline schemes that trivially include demand privacy or offline users in
known schemes.
