Worst-case secrecy rates in MIMOME systems under input and state constraints

We consider the maximization of worst-case secrecy rates for a multi-antenna wiretap channel under input constraints on the transmit covariance matrix and state constraints on the eavesdropper channel. This approach yields achievable rates (and the corresponding strategies) for a definitely secure transmission, although it is assumed that the transmitter does not have perfect information about the eavesdropper channel. We study problems with unitarily invariant constraints and show how these results can be applied to problems with more general constraints. Our results are illustrated with two detailed examples.