From Operational Models to Information Theory - Side Channels in pGCL with Isabelle

ABSTRACT. In this paper, we formally derive the probabilistic security predicate (expectation) for a guessing attack against a system with side-channel leakage, modelled in pGCL. Our principal theoretical contribution is to link the process-oriented view, where attacker and system execute particular model programs, and the information-theoretic view, where the attacker solves an optimal-decoding problem, viewing the system as a noisy channel. Our practical contribution is to illustrate the selection of probabilistic loop invariants to verify such security properties, and the demonstration of a mechanical proof linking traditionally distinct domains.