The Complexity of Synchronous Notions of Information Flow Security
This work addresses the complexity of security verification for synchronous systems, capturing timing-based attacks, which is an incremental advance over prior asynchronous-focused research.
The paper tackles the problem of verifying information flow security in synchronous finite state systems, showing that three security notions (nondeducibility on inputs, nondeducibility on strategies, and an unwinding-based notion) are decidable and characterizing their computational complexity.
The paper considers the complexity of verifying that a finite state system satisfies a number of definitions of information flow security. The systems model considered is one in which agents operate synchronously with awareness of the global clock. This enables timing based attacks to be captured, whereas previous work on this topic has dealt primarily with asynchronous systems. Versions of the notions of nondeducibility on inputs, nondeducibility on strategies, and an unwinding based notion are formulated for this model. All three notions are shown to be decidable, and their computational complexity is characterised.