Abstract
There is a clear intuitive connection between the notion of leakage of information in a program and concepts from Information Theory. We explore this connection by interpreting Information Theory as a security risk assessment of programs. Information Theory will then be used to introduce techniques to reason on looping constructs, which are the kind of programs that previous quantitative models failed to satisfactory address. The semantics here introduced allows to describe both the amount and rate of leakage; if either is small enough, then a program might be deemed “secure”. Using the semantics we provide an investigation and classification of bounded and unbounded covert channels.