Extending AADL for Security Design Assurance of Cyber-Physical Systems

Attacks such as the one that compromised the control systems for Iranian  centrifuges demonstrate a growing need to improve the design of security in cyber-physical systems. While much of the work on security  has focused on coding, many of the common weaknesses that lead to successful attacks are actually introduced by design. This technical report shows how important system-wide security properties can and must be described and validated at the architectural level. This is done  through the adoption and use of the Architecture Analysis and Design  Language (AADL) and a further extension of it to describe security  properties. This report demonstrates the viability and limitations of  this approach through an extended example that allows for specifying and analyzing the security properties of an automotive electronics system.  The report begins with a modeling of threats using the Microsoft STRIDE framework and then translates them into attack scenarios. Next, the report describes -- as AADL components, relationships, and properties -- the architectural structures, services, and properties needed to guard  against such attacks. Finally, the report shows how these properties can be validated at design time using a model checker such as Resolute and  discusses the limitations of this approach in addressing common security weaknesses.