Alceste Scalas

Florian Furbach, Lucas Clorius, Roland Kuhn et al.

Swarm protocols are a recently introduced formalism for specifying, implementing, and verifying peer-to-peer systems called swarms. A swarm consists of distributed agents called machines that communicate by asynchronous event propagation. Following a local-first model, each machine can progress without requiring continuous connectivity to other machines. Existing models of swarms are not compositional, making the modular development of large and complex swarm applications as well as the reuse of code difficult. We address these issues by presenting novel theory and techniques for the compositional specification, verification, and implementation of swarms. These results enable the correct compositional reuse of pre-existing swarm protocols and machine implementations. We implement these contributions in a companion software artifact which enables the automatic integration of independently designed and verified swarm components.

Ivan Prokić, Simona Prokić, Silvia Ghilezan et al.

This paper improves the session typing theory to support the modelling and verification of processes that implement federated learning protocols. To this end, we build upon the asynchronous ``bottom-up'' session typing approach by adding support for input/output operations directed towards multiple participants at the same time. We further enhance the flexibility of our typing discipline and allow for safe process replacements by introducing a session subtyping relation tailored for this setting. We formally prove safety, deadlock-freedom, liveness, and session fidelity properties for our session typing system. Moreover, we highlight the nuances of our session typing system, which (compared to previous work) reveals interesting interplays and trade-offs between safety, liveness, and the flexibility of the subtyping relation.

Jens Kanstrup Larsen, Alceste Scalas, Guy Amir et al.

This paper introduces NEST (Network-Enforced Session Types), a runtime verification framework that moves application-level protocol monitoring into the network fabric. Unlike prior work that instruments or wraps application code, we synthesize packet-level monitors that enforce protocols directly in the data plane. We develop algorithms to generate network-level monitors from session types and extend them to handle packet loss and reordering. We implement NEST in P4 and evaluate it on applications including microservice and network-function models, showing that network-level monitors can enforce realistic non-trivial protocols.

Massimo Bartoletti, Andrea Bracciali, Cristian Lepore et al.

We develop a formal model of Algorand stateless smart contracts (stateless ASC1.) We exploit our model to prove fundamental properties of the Algorand blockchain, and to establish the security of some archetypal smart contracts. While doing this, we highlight various design patterns supported by Algorand. We perform experiments to validate the coherence of our formal model w.r.t. the actual implementation.

Alceste Scalas, Massimo Bartoletti

Labelled Transition Systems (LTSs) are a fundamental semantic model in many areas of informatics, especially concurrency theory. Yet, reasoning on LTSs and relations between their states can be difficult and elusive: very simple process algebra terms can give rise to a large (possibly infinite) number of intricate transitions and interactions. To ease this kind of study, we present LTSwb, a flexible and extensible LTS toolbox: this tutorial paper discusses its design and functionalities.