  A polar coding scheme is proposed for the Wiretap Broadcast Channel with two
legitimate receivers and one eavesdropper. We consider a model in which the
transmitter wishes to send a private and a confidential message that must be
reliably decoded by the receivers, and the confidential message must also be
(strongly) secured from the eavesdropper. The coding scheme aims to use the
optimal rate of randomness and does not make any assumption regarding the
symmetry or degradedness of the channel. This paper extends previous work on
polar codes for the wiretap channel by proposing a new chaining construction
that allows to reliably and securely send the same confidential message to two
different receivers. This construction introduces new dependencies between the
random variables involved in the coding scheme that need to be considered in
the secrecy analysis.
