  We consider the MIMO wiretap channel, that is a MIMO broadcast channel where
the transmitter sends some confidential information to one user which is a
legitimate receiver, while the other user is an eavesdropper. Perfect secrecy
is achieved when the the transmitter and the legitimate receiver can
communicate at some positive rate, while insuring that the eavesdropper gets
zero bits of information. In this paper, we compute the perfect secrecy
capacity of the multiple antenna MIMO broadcast channel, where the number of
antennas is arbitrary for both the transmitter and the two receivers.
