Abstract: With the increasing scale of software application, once the software system fails, property loss or casualties can hardly be avoided. Therefore, it is particularly important to evaluate the trustworthiness of the software. In safetycritical areas such as aerospace, security, as one of the key attributes of trustworthiness, affects the trustworthiness evaluation of the entire software system. Especially when an attack or defect occurs, the trustworthiness of the component will decrease, which will affect the trustworthiness of its security associated components. Moreover, it will affect the trustworthiness of the whole system. Follow the idea, the formulas are designed to measure the impact of the change of the trustworthiness of a component on the other components. Furthermore, we propose the componentdependence measurementtrustworthiness model (CDMTM) of the entire software system. Finally, taking a certain “aerospace power management equipment” as an example, we prove the rationality and effectiveness of the CDMTM established in this paper.

Key words: software, security, trustworthy systems, trustworthy dependence relations