A Better Composition Operator For Quantitative Information Flow Analyses

Given a description of the quantitative information flow (qif) for components, how can we determine the qif of a system composed from components? We explore this fundamental question mathematically and provide an answer based on a new composition operator. We investigate its properties and prove that it generalises existing composition operators. We illustrate the results with a fresh look on Chaum's dining cryptographers. We show that the new operator enjoys various convenient algebraic properties and that it is well-behaved under composition refinement.