  The wiretap channel model of Wyner is one of the first communication models
with both reliability and security constraints. Capacity-achieving schemes for
various models of the wiretap channel have received considerable attention in
recent literature. In this paper, we show that capacity of the general (not
necessarily degraded or symmetric) wiretap channel under a "strong secrecy
constraint" can be achieved using a transmission scheme based on polar codes.
We also extend our construction to the case of broadcast channels with
confidential messages defined by Csisz{\'a}r and K{\"orner}, achieving the
entire capacity region of this communication model.
