We investigate the demand private coded caching problem, which is an $(N,K)$ coded caching problem with $N$ files, $K$ users, each equipped with a cache of size $M$, and an additional privacy constraint on user demands. We first present a new virtual-user-based achievable scheme for arbitrary number of users and files. Then, for the case of 2 files and arbitrary number of users, we derive some new converse bounds. As a result, we obtain the exact memory-rate tradeoff of the demand private coded caching problem for 2 files and 3 users. As for the case of 2 files and arbitrary number of users, the exact memory-rate tradeoff is characterized for $M\in [0,\frac{2}{K}] \cup [\frac{2(K-1)}{K+1},2]$.

翻译：我们研究了需求私有编码缓存问题，这是一个包含 $N$ 个文件、$K$ 个用户（每个用户配备大小为 $M$ 的缓存）且额外具有用户需求隐私约束的 $(N,K)$ 编码缓存问题。我们首先提出了一种新的基于虚拟用户的可实现方案，适用于任意数量的用户和文件。随后，针对两文件与任意用户数量的情形，推导出若干新的逆界。由此，我们得到了两文件三用户情形下需求私有编码缓存问题的精确内存-速率权衡。对于两文件与任意用户数量的情形，当 $M\in [0,\frac{2}{K}] \cup [\frac{2(K-1)}{K+1},2]$ 时，精确内存-速率权衡被完整刻画。