The communication complexity of achieving SK capacity in a class of PIN models

The communication complexity of achieving secret key (SK) capacity in the multiterminal source model of Csiszár and Narayan is the minimum rate of public communication required to generate a maximal-rate SK. It is well known that the minimum rate of communication for omniscience, denoted by RCO, is an upper bound on the communication complexity, denoted by RSK. A source model for which this upper bound is tight is called RSK-maximal. In this paper, we establish a sufficient condition for RSK-maximality within the class of pairwise independent network (PIN) models defined on hypergraphs. This allows us to compute RSK exactly within the class of PIN models satisfying this condition. On the other hand, we also provide a counterexample that shows that our condition does not in general guarantee RSK-maximality for sources beyond PIN models.