YAPA: A generic tool for computing intruder knowledge

TL;DR

This paper introduces YAPA, a versatile tool that computes attacker knowledge in security protocols by providing a generic algorithm applicable to any convergent rewrite system, unifying and extending existing decision procedures.

Contribution

The paper presents a generic, implementable algorithm for deducibility and static equivalence applicable to all convergent rewrite systems, filling a gap in existing tools.

Findings

YAPA covers most existing decision procedures for convergent theories.

The implementation of YAPA is efficient and comparable to ProVerif and KiSs.

YAPA unifies various decision procedures into a single generic framework.

Abstract

Reasoning about the knowledge of an attacker is a necessary step in many formal analyses of security protocols. In the framework of the applied pi calculus, as in similar languages based on equational logics, knowledge is typically expressed by two relations: deducibility and static equivalence. Several decision procedures have been proposed for these relations under a variety of equational theories. However, each theory has its particular algorithm, and none has been implemented so far. We provide a generic procedure for deducibility and static equivalence that takes as input any convergent rewrite system. We show that our algorithm covers most of the existing decision procedures for convergent theories. We also provide an efficient implementation, and compare it briefly with the tools ProVerif and KiSs.