  In this letter, we study a rate-splitting multiple access (RSMA)-based
intelligent reflecting surface (IRS)-aided multi-user multiple-input
single-output (MISO) secure communication system with a potential eavesdropper
(Eve). Aiming to maximize the minimum secrecy rate (SR) among all the
legitimate users (LUs), a design problem for jointly optimizing the transmit
beamforming with artificial noise (AN), the IRS beamforming, and the secrecy
common rate allocation is formulated. Since the design problem is highly
non-convex with coupled optimization variables, we develop a computationally
efficient algorithm based on the alternating optimization (AO) technique to
solve it suboptimally. Numerical results demonstrate that the proposed design
can significantly improve the max-min SR over the benchmark schemes without IRS
or adopting other multiple access techniques. In particular, employing the RSMA
strategy can substantially reduce the required numbers of IRS elements for
achieving a target level of secrecy performance compared with the benchmark
schemes.
