  Graph-based assessment formalisms have proven to be useful in the safety,
dependability, and security communities to help stakeholders manage risk and
maintain appropriate documentation throughout the system lifecycle. In this
paper, we propose a set of methods to automatically construct security argument
graphs, a graphical formalism that integrates various security-related
information to argue about the security level of a system. Our approach is to
generate the graph in a progressive manner by exploiting logical relationships
among pieces of diverse input information. Using those emergent argument
patterns as a starting point, we define a set of extension templates that can
be applied iteratively to grow a security argument graph. Using a scenario from
the electric power sector, we demonstrate the graph generation process and
highlight its application for system security evaluation in our prototype
software tool, CyberSAGE.
