For the above reasons, in this paper, we study the design of synchronized large-scale CRNGs and its application to secure communication. In order to simplify the presentation of the paper, we choose Duffing map for this study. However, the proposed modulation approach can also effectively applied to other classes of discrete chaotic systems. First, we introduce a modulation approach by introducing some parameters into the chaotic Duffing map to regulate and increase the diversity of chaotic state responses. Then we implement the proposed modulated Duffing map systems under different initial conditions by the microcontroller. Due to the butterfly effect, the state response of each Duffing map system will be quite different. Therefore, we can get a large amount of random chaotic states and complete the design of large-scale CRNGs. For subsequent communication security application, we use sliding mode control to cope with the synchronization problem of the master-slave large-scale CRNGs. Finally,theaboveresultsareintegratedtorealizeaninnovativesecurecommunicationsystem to prove the correctness and feasibility of the research.