Optimal Memory-Rate Tradeoff in Secure Coded Caching for Small Buffer or Small Rate
Han Fang, Nan Liu, Wei Kang · 2024
We consider the secure coded caching problem proposed by Ravindrakumar et. al where no user can obtain information about files other than the one requested. We find the optimal delivery rate for the case of cache size$M=1$and the minimum cache size required when the worst-case delivery rate$R=1$for arbitrary number of users and files. These optimal results are found by proposing two new linear schemes, and characterizing new properties of secure coded caching schemes and converse results for the case of$M=1$or$R=1$. As a result, the two end-points of the optimal memory-rate tradeoff curve is fully characterized for the secure coded caching problem.