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.

翻译：Maddah-Ali和Niesen（MAN）提出的编码缓存是一种模型，其中服务器向具有本地缓存的用户广播多播数据包，利用该本地缓存来降低峰值网络通信负载。原始MAN模型未考虑需求缺失（即某些用户可能未请求文件）或隐私问题（即解码多播数据包可能暴露用户的需求）。前者通过包含离线用户的热插拔模型加以描述，在该模型中，服务器在收到一定数量的文件请求后开始发送多播数据包。后者则通过将部分缓存用于存储隐私密钥来解决，这些密钥帮助用户解码其请求的文件，同时完全不知晓其他用户的需求。本文研究了热插拔模型中针对合作用户的私有需求问题，该模型包含离线用户。提出了两种基于最大距离可分（MDS）码的可实现方案。与现有方案中简单包含需求隐私或离线用户的基线方案相比，所提方案在小子包化程度和小内存场景下实现了更低的负载。