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.
