Enhancing Airworthiness Security: SysML-Based Approach to Modelling Security Scope Definitions

Airworthiness certification of aircraft requires an Airworthiness Security Process (AWSP) to ensure safe operation under potential unauthorized interactions, particularly in the context of growing cyber threats. Regulatory authorities mandate the consideration of Intentional Unauthorized Electronic Interactions (IUEI) in the development of aircraft, airborne software, and equipment. As the industry increasingly adopts Model-Based Systems Engineering (MBSE) to accelerate development, we aim to enhance this effort by focusing on security scope definitions – a critical step within the AWSP for security risk assessment that establishes the boundaries and extent of security measures. However, our findings indicate that, despite the increasing use of model-based tools in development, these security scope definitions often remain either document-based or, when modeled, are presented at overly abstract levels, both of which limit their utility. Furthermore, we found that these definitions frequently lack alignment with airworthiness security regulations. To address these two distinct gaps, this paper presents a model-based approach for detailed security scope definitions using the Systems Modelling Language (SysML). Our approach aligns with airworthiness security regulations ED-202A / DO-326A and ED-203A / DO-356A and incorporates a SysML profile based on the CORAS language for accurate modeling of security scopes. This facilitates a model-based security risk assessment by creating unambiguously system models that represent assets through model elements, document entry points to the assets and determine their environment. This SysML-based approach supports certification related activities by ensuring that security scope definitions are comprehensive and aligned with airworthiness regulations, directly addressing the identified gaps. The approach's applicability and effectiveness are demonstrated through an illustrative example in the domain of aircraft cabin system development. Moreover, the approach provides valuable inputs that assist operators in deriving guidance for the safe operation and maintenance of the aircraft, complementing existing methods and practices.