Mutual dependence for secret key agreement

A mutual dependence expression is established for the secret key agreement problem when all users are active. In certain source networks, the expression can be interpreted as certain notions of connectivity and network information flow. In particular, the secrecy problem can be mapped to a new class of network coding problems with selectable links and undirected broadcast links. For such networks, the secrecy capacities serve as upper bounds on the maximum network throughputs, while the network coding solutions can be used for secret key agreement.