The Secrecy Capacity Region of the Gaussian MIMO Multi-Receiver Wiretap Channel

In this paper, the authors consider the Gaussian Multiple-Input Multiple-Output (MIMO) multi-receiver wiretap channel in which a transmitter wants to have confidential communication with an arbitrary number of users in the presence of an external eavesdropper. They derive the secrecy capacity region of this channel for the most general case. They first show that even for the Single-Input Single-Output (SISO) case, existing converse techniques for the Gaussian scalar broadcast channel cannot be extended to this secrecy context, to emphasize the need for a new proof technique.