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.