Cross-Tool Semantics for Protocol Security Goals

Formal protocol analysis tools provide objective evidence that a protocol under standardization meets security goals, as well as counterexamples to goals it does not meet (“attacks”). Different tools are however based on different execution semantics and adversary models. If different tools are applied to alternative protocols under standardization, can formal evidence offer a yardstick to compare the results? We propose a family of languages within first order predicate logic to formalize protocol safety goals (rather than indistinguishability). Although they were originally designed for the strand space formalism that supports the tool CPSA, we show how to translate them to goals for the applied π calculus that supports the tool ProVerif. We give a criterion for protocols expressed in the two formalisms to correspond, and prove that if a protocol in the strand space formalism satisfies a goal, then a corresponding applied π process satisfies the translation of that goal. We show that the converse also holds for a class of goal formulas, and conjecture a broader equivalence. We also describe a compiler that, from any protocol in the strand space formalism, constructs a corresponding applied π process and the relevant goal translation.