  This paper addresses the problem that designing the transmit waveform and
receive beamformer aims to maximize the receive radar SINR for secure
dual-functional radar-communication (DFRC) systems, where the undesired
multi-user interference (MUI) is transformed to useful power. In this system,
the DFRC base station (BS) serves communication users (CUs) and detects the
target simultaneously, where the radar target is regarded to be malicious since
it might eavesdrop the transmitted information from BS to CUs. Inspired by the
constructive interference (CI) approach, the phases of received signals at CUs
are rotated into the relaxed decision region, and the undesired MUI is designed
to contribute in useful power. Then, the convex approximation method (SCA) is
adopted to tackle the optimization problem. Finally, numerical results are
given to validate the effectiveness of the proposed method, which shows that it
is viable to ensure the communication data secure adopting the techniques that
we propose.
