text: abstract. quantitative information flow (qif) is concerned with measuring how much of a secret is leaked to an adversary who observes the
  result of a computation that uses it. prior work has shown that qif techniques based on abstract interpretation with probabilistic polyhedra can be
  used to analyze the worst-case leakage of a query, on-line, to determine
  whether that query can be safely answered. while this approach can
  provide precise estimates, it does not scale well. this paper shows how
  to solve the scalability problem by augmenting the baseline technique
  with sampling and symbolic execution. we prove that our approach never
  underestimates a query’s leakage (it is sound), and detailed experimental
  results show that we can match the precision of the baseline technique
  but with orders of magnitude better performance.