Hybrid Information Flow Monitoring Against Web Tracking

International audienceMotivated by the problem of stateless web tracking (fingerprinting), we propose a novel approach to hybrid information flow monitoring by tracking the knowledge about secret variables using logical formulae. This knowledge representation helps to compare and improve precision of hybrid infor- mation flow monitors. We define a generic hybrid monitor parametrised by a static analysis and derive sufficient conditions on the static analysis for sound- ness and relative precision of hybrid monitors. We instantiate the generic monitor with a combined static constant and dependency analysis. Several other hybrid monitors including those based on well-known hybrid techniques for information flow control are formalised as instances of our generic hybrid monitor. These monitors are organised into a hierarchy that establishes their relative precision. The whole framework is accompanied by a formalisation of the theory in the Coq proof assistant