This paper characterizes the secret message capacity of three networks where two unicast
sessions share some of the communication resources. Each network consists of erasure
channels with state feedback. A passive eavesdropper is assumed to wiretap any one of the
links. The capacity achieving schemes as well as the outer bounds are formulated as linear
programs. The proposed strategies are then numerically evaluated and shown to achieve
higher rate performances (up to a double single-or sum-rate) with respect to alternative …

This paper considers a class of wireline networks, derived from the well-known butterfly
network, over which two independent unicast sessions take place simultaneously. The main
objectives are to understand when network coding type of operations are beneficial with and
without security considerations and to derive the gains that cooperation among sources and
sinks can bring. Towards these goals, the capacity region of the butterfly network with
arbitrary edge capacities is first derived. It is then shown that no rate can be guaranteed over …