On the role of Abstract Non-Interference in language-based security

In this paper, we illustrate the role of the notion of Abstract Non-Interference in language based security, by explaining how it models both the weakening of attackers' observational capability, and the declassification of private information. Namely, we show that in abstract non-interference we model both attackers that can only observe properties of public data, and private properties that can or cannot flow. Moreover, we deepen the understanding of abstract non-interference by comparing it, by means of examples, with some the most interesting approaches to the weakening of non-interference, such as the PER model, robust declassification, delimited release and relaxed non-interference.