  A collaboration network is a graph formed by communication channels between
parties. Parties communicate over these channels to establish secrets,
simultaneously enforcing interdependencies between the secrets. The paper
studies properties of these interdependencies that are induced by the topology
of the network. In previous work, the authors developed a complete logical
system for one such property, independence, also known in the information flow
literature as nondeducibility. This work describes a complete and decidable
logical system for the functional dependence relation between sets of secrets
over a collaboration network. The system extends Armstrong's system of axioms
for functional dependency in databases.
