A dual-layer vector map encryption scheme using 4D hyperchaos and SM4

Vector map data, as a fundamental component of national geographic information, plays a strategic role in areas such as national security, urban planning, and smart city development. However, with the rapid advancement of information technology, vector map data faces increasing security challenges during transmission and storage. On the one hand, traditional coordinate-scrambling methods are vulnerable to reverse analysis since the numerical values remain essentially unchanged. On the other hand, some existing approaches rely on low-dimensional chaotic systems, which are prone to short periods and dynamical degradation, thereby reducing randomness and security. To address these challenges, this paper proposes a dual-layer encryption method for vector maps that integrates a four-dimensional hyperchaotic system with the national cryptographic algorithm SM4. In this method, the four-dimensional hyperchaotic system generates multiple high-randomness sequences, from which sequences are dynamically selected to scramble coordinates and thereby alter the spatial topological relationships. Furthermore, the chaotic sequences are employed to generate dynamic SM4 keys and initialization vector, enabling deep encryption of coordinate values. Experimental results demonstrate that the proposed method not only effectively protects the three types of vector data-points, polylines, and polygons-but also exhibits significant advantages in resisting brute-force attacks, differential attacks, and low-dimensional chaotic degradation. Overall, it substantially enhances the security and applicability of vector map data during transmission and storage.