The lattice model proposed by Denning in her seminal work provided secure information flow analyses with an intuitive and uniform mathematical foundation. Different organisations, however, may employ quite different security lattices. In this paper, we propose a connection framework that permits different organisations to exchange information while maintaining both security of information flows as well as their autonomy in formulating and maintaining security policy. Our prescriptive framework is based on the rigorous mathematical framework of Lagois connections given by Melton, together with a simple operational model for transferring object data between domains. The merit of this formulation is that it is simple, minimal, adaptable and intuitive, and provides a formal framework for establishing secure information flow across autonomous interacting organisations. We show that our framework is semantically sound, by proving that the connections proposed preserve standard correctness notions such as non-interference.
Starting from a denotational semantics of the eager untyped lambda-calculus with explicit runtime errors, the standard collecting semantics is defined as specifying the strongest program properties. By a first abstraction, a new sound type collecting semantics is derived in compositional fix-point form. Then by successive (semi-dual) Galois connection based abstractions, type systems and or type inference algorithms are designed as abstract semantics or abstract interpreters approximating the type collecting semantics. This leads to a hierarchy of type systems, which is part of the lattice of abstract interpretations of the untyped lambda-calculus. This hierarchy includes two new � la Church Curry polytype systems. Abstractions of this polytype semantics lead to classical Milner Mycroft and Damas Milner polymorphic type schemes, Church Curry monotypes and Hindley principal typing algorithm. This shows that types are abstract interpretations. We introduce an enhanced information-flow analysis for tracking the amount of confidential data that is possibly released to third parties by a mobile application. The main novelty of our solution is that it can explicitly keep track of the footprint of data sources in the expressions formed and manipulated by the program, as well as of transformations over them, yielding a lazy approach with finer granularity, which may reduce false positives with respect to state-of-the-art information-flow analyses. We introduce an abstract domain for information-flow analysis of software. The proposal combines variable dependency analysis with numerical abstractions, yielding to accuracy and efficiency improvements. We apply the full power of the proposal to the case of database query languages as well. Finally, we present an implementation of the analysis, called ( Sails ), as an instance of a generic static analyzer. Keeping the modular construction of the analysis, the tool allows one to tune the granularity of heap analysis and to choose the numerical domain involved in the reduced product. This way the user can tune the information leakage analysis at different levels of precision and efficiency. 