Recently, the secrecy capacity of the multi-antenna wiretap channel was
characterized by Khisti and Wornell [1] using a Sato-like argument. This note
presents an alternative characterization using a channel enhancement argument.
This characterization relies on an extremal entropy inequality recently proved
in the context of multi-antenna broadcast channels, and is directly built on
the physical intuition regarding to the optimal transmission strategy in this
communication scenario.Comment: 10 pages, 0 figure

Liu, Tie