On Secure Capacity of Multiple Unicast Traffic over Two-Layer Networks.

This paper studies the problem of secure communication over two-layer networks, where a source is connected to a set of relays via direct edges. These relays are then connected to $m$ destinations, such that each destination has direct connections to a subset of relays. In multiple unicast traffic, the source wishes to transmit independent information to each of the $m$ destinations. This work studies the secure capacity region for this traffic over the defined two-layer networks, under the assumption of perfect information theoretic security criterion from an adversary who can access any $K$ edges of the network. In particular, the secure capacity region is characterized when either $K=1$ or $m=3$. Moreover, conditions sufficient to characterize the secure capacity region are provided for arbitrary values of $K$ and $m$.