Abstract
Reconfigurable Intelligent Surface (RIS) is applied to physical layer security to enhance the security of task offloading in mobile edge computing (MEC) systems. However, due to the "double fading" effect on the reflection link, the deployment of passive RIS can only achieve limited performance gains. In view of these, active RIS is regarded as a prospective candidate for compensating for the "double fading" effect of passive RIS due to its low-power integrated amplifiers. This paper proposes a novel secure MEC system, which improves the communication and computation performance of the system by introducing active RIS. Specifically, we aim to minimize the weighted total energy consumption (TEC) in an active RIS-assisted MEC system, subject to the constraints of secure offloading and the phase shift of the active RIS. To address this non-convex problem, block coordinate descent (BCD) and successive convex approximation (SCA) methods are employed to alternately optimize the subproblems. Under the premise of ensuring the secure transmission rate for users, the computation offloading volume, the edge computing resource allocation, beamforming at the receiver, and reflection coefficient matrix at the active RIS are jointly optimized. Simulation results demonstrate that the active RIS significantly enhances the weighted TEC performance in MEC systems while ensuring secure transmission rates, effectively mitigating the impact of the "double fading" effect, and showing notable advantages over existing passive RIS and non-RIS schemes.