Simultaneously generating multiple keys over a cascade of a noiseless channel and a wiretap channel

In this paper, the problem of simultaneously generating multiple keys over a cascade of a noiseless channel and a wiretap channel is considered. The problem consists of three legitimate parties, i.e., Alice, Bob and Carol, where Alice and Bob wish to agree with Carol on independent secret keys. Alice and Bob are connected via a noiseless channel, and Bob is connected with Carol via a wiretap channel, while there is no direct connection between Alice and Carol. To Alice and Carol, Bob acts as a relay. Under this model, a single-letter characterization of the secret-key capacity region is provided. The result shows that there exists a trade-off between the individual secret-key rates.