hess.ea:pspsp:2025 ArticleInAPeriodical IOS Press 2025 November Journal of Computer Security 33 6 https://doi.org/10.1177/0926227X251358741 HessAndreasViktor MödersheimSebastianAlexander BruckerAchimD SchlichtkrullAnders PSPSP: A Tool for Automated Verification of Stateful Protocols in Isabelle/HOL In protocol verification we observe a wide spectrum from fully automated methods to interactive theorem proving with proof assistants like Isabelle/HOL. The latter provide overwhelmingly high assurance of the correctness, which automated methods often cannot: due to their complexity, bugs in such automated verification tools are likely and thus the risk of erroneously verifying a flawed protocol is non-negligible. There are a few works that try to combine advantages from both ends of the spectrum: a high degree of automation and assurance. We present here a first step towards achieving this for a more challenging class of protocols, namely those that work with a mutable long-term state. To our knowledge this is the first approach that achieves fully automated verification of stateful protocols in an LCF-style theorem prover. The approach also includes a simple user-friendly transaction-based protocol specification language embedded into Isabelle, and can also leverage a number of existing results such as soundness of a typed model.