  Simultaneous wireless information and power transfer (SWIPT) and intelligent
reflecting surface (IRS) are two promising techniques for providing enhanced
wireless communication capability and sustainable energy supply to
energy-constrained wireless devices. Moreover, the combination of the IRS and
the SWIPT can create the "one plus one greater than two" effect. However, due
to the broadcast nature of wireless media, the IRS-aided SWIPT systems are
vulnerable to eavesdropping. In this paper, we study the security issue of the
IRS-aided SWIPT systems. The objective is to maximize the secrecy rate by
jointly designing the transmit beamforming and artificial noise (AN) covariance
matrix at a base station (BS) and reflective beamforming at an IRS, under
transmit power constraint at the BS and energy harvesting (EH) constraints at
multiple energy receivers. To tackle the formulated non-convex problem, we
first employ an alternating optimization (AO) algorithm to decouple the
coupling variables. Then, reflective beamforming, transmit beamforming and AN
covariance matrix can be optimized by using a penalty-based algorithm and
semidefinite relaxation (SDR) method, respectively. Simulation results
demonstrate the effectiveness of the proposed scheme over baseline schemes.
