  This paper investigates the spectrum sharing between a multiple-input
single-output (MISO) secure communication system and a multiple-input
multiple-output (MIMO) radar system in the presence of one suspicious
eavesdropper. We jointly design the radar waveform and communication
beamforming vector at the two systems, such that the interference between the
base station (BS) and radar is reduced, and the detrimental radar interference
to the communication system is enhanced to jam the eavesdropper, thereby
increasing secure information transmission performance. In particular, by
considering the imperfect channel state information (CSI) for the user and
eavesdropper, we maximize the worst-case secrecy rate at the user, while
ensuring the detection performance of radar system. To tackle this challenging
problem, we propose a two-layer robust cooperative algorithm based on the
S-lemma and semidefinite relaxation techniques. Simulation results demonstrate
that the proposed algorithm achieves significant secrecy rate gains over the
non-robust scheme. Furthermore, we illustrate the trade-off between secrecy
rate and detection probability.
