This paper derives upper and lower bounds on the secrecy capacity-memory tradeoff of a wiretap erasure broadcast channel (BC) with Kw weak receivers and Ks strong receivers, where weak receivers and strong receivers have the same erasure probabilities and cache sizes, respectively. The lower bounds are achieved by the schemes that meticulously combine joint cache-channel coding with wiretap coding and key-aided onetime pads. The presented upper bound holds more generally for arbitrary degraded BCs and arbitrary cache sizes. When only weak receivers have cache memories, upper and lower bounds coincide for small and large cache memories, thus providing the exact secrecy capacity-memory tradeoff for this setup. The derived bounds further allow us to conclude that the secrecy capacity is positive even when the eavesdropper is stronger than all the legitimate receivers with cache memories. Moreover, they show that the secrecy capacity-memory tradeoff can be significantly smaller than its non-secure counterpart, but it grows much faster when cache memories are small. This paper also presents a lower bound on the global secrecy capacity-memory tradeoff where one is allowed to optimize the cache assignment subject to a total cache budget. It is close to the best known lower bound without secrecy constraint. For small total cache budget, the global secrecy capacity-memory tradeoff is achieved by assigning all the available cache memory uniformly over all the receivers if the eavesdropper is stronger than all the legitimate receivers, and it is achieved by assigning the cache memory uniformly only over the weak receivers if the eavesdropper is weaker than the strong receivers.

We consider a K-receiver wiretap broadcast channel where Kw receivers are weak and have cache memories and Ks receivers are strong and have no cache memories. We derive an upper bound on the secrecy rate-memory tradeoff under a joint secrecy constraint and under decentralized caching. In contrast to previous works, prefetching in our scheme is purely decentralized and receivers randomly sample from a random key stream available at the transmitter and from the files in a library. For small cache sizes, the performance of our scheme improves with increasing length of the random key stream. For moderate and large cache sizes, a small key stream suffices to perform close to the information-theoretic limit of the system.

We derive upper and lower bounds on the secure capacity-memory tradeoff of the K-user (K > 2) wiretap erasure broadcast channel where Kwreceivers are weak and have cache memories of equal size, and Ksreceivers are strong and have no cache. The bounds coincide for small and large cache memories. The lower bound also exhibits that cache memories provide larger gains under a secrecy constraint than without such a constraint. The lower bound is based on a joint cache-channel coding scheme that simultaneously exploits the cache contents and the channel statistics. Moreover, we show for the two-user scenario that in the regime of small cache memories, the capacity-memory tradeoff is larger when only the weaker receiver has cache memory than when this cache memory is split equally among the two receivers.

The paper studies the wiretap erasure broadcast channel (BC) with an external eavesdropper when the legitimate receivers have cache memories. Various secure coding schemes are proposed for a scenario where Kwweak receivers have same erasure probabilities and Ksstrong receivers have same erasure probabilities. The coding schemes achieve the cache-aided secrecy capacity when only weak receivers have cache memories and this cache memory is either small or large. They also allow to conclude the following: 1) Under a total cache budget it is often beneficial to assign the cache memories unequally between strong and weak receivers. 2.) Joint cache-channel coding is necessary to attain the optimal performance. 3.) The secrecy capacity can be positive even when the eavesdropper is stronger than the legitimate receivers.

We derive upper and lower bounds on the secure capacity-memory tradeoff of the two-user wiretap erasure BC with cache memory at the weaker receiver. The bounds coincide when the cache memory exceeds a given threshold. The lower bound also exhibits that cache memories provide larger gains under a secrecy constraint than without such a constraint. Moreover, for a large set of parameters the capacity-memory tradeoff is larger if only the weaker receiver has cache memory than when this cache memory is split equally among the receivers. The lower bound is based on a joint cache-channel coding scheme that simultaneously exploits the cache contents and the channel statistics. Such a joint design yields significant gains over a separation-based design.