Cybersecurity risk assessment of nuclear SVDU based on attack tree

The nuclear safety video display unit (SVDU) is a critical human-machine interface in the nuclear reactor protection system, and its cybersecurity is increasingly challenged by the sector's full digitalization. This paper proposes a novel cybersecurity risk assessment method integrating an attack tree model with the STRIDE threat framework to evaluate the risk status of the nuclear SVDU. The approach innovatively incorporates the latest CVSS4.0 standard to define security attributes (attack cost, technical difficulty, discovery difficulty, and impact) for leaf nodes, which are quantified through hierarchical scoring. Crucially, an objective entropy weighting method is employed to calculate the weights of these attributes, effectively eliminating the subjective bias inherent in traditional expert-dependent methods like FAHP. The risk probability is then propagated from leaf to root nodes based on their dependency relationships. Comparative analysis demonstrates that the proposed method offers a more sensitive and discriminating assessment, identifying critical threats that subjective approaches might overlook and providing a robust, data-driven basis for prioritizing security protection strategies.