In space-air-ground integrated networks (SAGIN)-enabled IoT networks, secure access has become a significant challenge due to the increasing risks of eavesdropping attacks. To address these threats to data confidentiality, this paper proposes a Digital Twin (DT)-driven secure access strategy. The strategy leverages a virtual replica of the physical SAGIN environment within the DT framework to continuously assess dynamic eavesdropping risks by quantifying secrecy capacity. Operating within this DT framework, an evolutionary game model dynamically balances the DT-updated secrecy capacity against queuing delay, steering IoT devices toward more secure and efficient access decisions. Furthermore, a novel distributed algorithm, integral to the DT operation, is developed to obtain the equilibrium access strategy for each device in a scalable manner. Simulation results demonstrate that the proposed DT-based approach substantially improves the security of SAGIN-enabled IoT networks. Additionally, it effectively balances system load, prevents overload occurrences, and decreases queuing delay compared to benchmark schemes, thereby comprehensively improving overall network performance.

翻译：在天地一体化网络（SAGIN）赋能的物联网网络中，由于窃听攻击风险的日益增加，安全接入已成为一项重大挑战。为应对这些对数据机密性的威胁，本文提出了一种数字孪生（DT）驱动的安全接入策略。该策略利用DT框架内物理SAGIN环境的虚拟副本，通过量化保密容量来持续评估动态窃听风险。在此DT框架内，一个演化博弈模型动态地平衡DT更新的保密容量与排队时延，引导物联网设备做出更安全、更高效的接入决策。此外，作为DT操作的核心部分，本文开发了一种新颖的分布式算法，以可扩展的方式为每个设备获取均衡接入策略。仿真结果表明，所提出的基于DT的方法显著提升了SAGIN赋能物联网网络的安全性。此外，与基准方案相比，该方法有效平衡了系统负载，防止了过载发生，并降低了排队时延，从而全面提升了整体网络性能。