  We study the Gaussian MIMOME wiretap channel where a transmitter wishes to
communicate a confidential message to a legitimate receiver in the presence of
eavesdroppers, while the eavesdroppers should not be able to decode the
confidential message. Each node in the network is equipped with arbitrary
number of antennas. Furthermore, channels are time varying, and there is no
channel state information available at the transmitter (CSIT) with respect to
eavesdroppers' channels; and transmitter only has access to delayed CSIT of the
channel to the legitimate receiver. The secure degrees of freedom (SDoF) for
such network has only been characterized for special cases, and is unknown in
general. We completely characterize the SDoF of this network for all antenna
configurations. In particular, we strictly improve the state-of-the-art
achievable scheme for this network by proposing more efficient artificial noise
alignment at the receivers. Furthermore, we develop a tight upper bound by
utilizing 4 important inequalities that provide lower bounds on the received
signal dimensions at receivers which supply delayed CSIT or no CSIT, or at a
collection of receivers where some supply no CSIT. These inequalities together
allow for analysis of signal dimensions in networks with asymmetric CSIT; and
as a result, we present a converse proof that leads to characterization of SDoF
for all possible antenna configurations.
