Secret-key capacity of infinite compound sources with communication rate constraint

For secret-key generation by using a compound source, the actual statistics of the source are unknown to the participants. It is assumed that the probability distribution of the source belongs to a set which is known to the participants. The secret-key generation protocol should guarantee in this case the reliability and security of the generated secret-key simultaneously for all possible source statistics which belong to this set. At the same time, the communication rate between the legitimate users should not exceed a given communication rate parameter. In this work, this problem is studied for the case where the set of source states is arbitrary (possibly infinite) and the set of marginals (transmitter's states) is finite. The secret-key capacity is completely characterized as a function of the forward communication rate parameter between the legitimate users.