Quantum Information-Flow Security: Noninterference and Access Control
This work addresses security issues in quantum computing and communication systems, providing foundational tools for a domain where classical methods fail, though it is incremental in extending existing formal methods to quantum contexts.
The paper tackles the problem of information-flow security in quantum systems, which had been largely unaddressed, by defining an automata model to rigorously reason about it, generalizing classical noninterference to quantum settings, and proving security for access control.
Quantum cryptography has been extensively studied in the last twenty years, but information-flow security of quantum computing and communication systems has been almost untouched in the previous research. Duo to the essential difference between classical and quantum systems, formal methods developed for classical systems, including probabilistic systems, cannot be directly applied to quantum systems. This paper defines an automata model in which we can rigorously reason about information-flow security of quantum systems. The model is a quantum generalisation of Goguen and Meseguer's noninterference. The unwinding proof technique for quantum noninterference is developed, and a certain compositionality of security for quantum systems is established. The proposed formalism is then used to prove security of access control in quantum systems.