Lagrange multipliers and maximum information leakage in different observational models

This paper explores two fundamental issues in Language based security. The first is to provide a quantitative definition of information leakage valid in several attacker's models. We consider attackers with different capabilities; the strongest one is able to observe the value of the low variables at each step during the execution of a program; the weakest one can only observe a single low value at some stage of the execution.