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Documents authored by Gorla, Daniele

Document
DOI: 10.4230/LIPIcs.ECOOP.2026.19
Typing Fallback Functions: A Semantic Approach to Type Safe Smart Contracts

Authors: Stian Lybech, Daniele Gorla, and Luca Aceto

Published in: LIPIcs, Volume 372, 40th European Conference on Object-Oriented Programming (ECOOP 2026)

Abstract
This paper develops semantic typing in a smart-contract setting to ensure type safety of code that uses statically untypable language constructs, such as the fallback function. The idea is that the creator of a contract on the blockchain equips code containing such constructs with a formal proof of its type safety, given in terms of the semantics of types. Then, a user of the contract only needs to check the validity of the provided "proof certificate" of type safety. This is a form of proof-carrying code, which naturally fits with the immutable nature of the blockchain environment. As a concrete application of our approach, we focus on ensuring information flow control and non-interference for TinySol, a distilled version of the Solidity language, through security types. We provide the semantics of types in terms of a typed operational semantics of TinySol and we express the proofs of safety as coinductively-defined typing interpretations, which can be represented compactly via up-to techniques, similar to those used for bisimilarity. We also show how our machinery can be used to type the typical pointer-to-implementation pattern based on the fallback function and to reject a distilled version of the infamous Parity Multisig Wallet Attack.
Cite as

Stian Lybech, Daniele Gorla, and Luca Aceto. Typing Fallback Functions: A Semantic Approach to Type Safe Smart Contracts. In 40th European Conference on Object-Oriented Programming (ECOOP 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 372, pp. 19:1-19:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{lybech_et_al:LIPIcs.ECOOP.2026.19,
  author =	{Lybech, Stian and Gorla, Daniele and Aceto, Luca},
  title =	{{Typing Fallback Functions: A Semantic Approach to Type Safe Smart Contracts}},
  booktitle =	{40th European Conference on Object-Oriented Programming (ECOOP 2026)},
  pages =	{19:1--19:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-423-9},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{372},
  editor =	{Krebbers, Robbert and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2026.19},
  URN =		{urn:nbn:de:0030-drops-261159},
  doi =		{10.4230/LIPIcs.ECOOP.2026.19},
  annote =	{Keywords: semantic typing, smart contracts, information flow control, non-interference}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2025.39
Denotational Semantics for Probabilistic and Concurrent Programs

Authors: Noam Zilberstein, Daniele Gorla, and Alexandra Silva

Published in: LIPIcs, Volume 348, 36th International Conference on Concurrency Theory (CONCUR 2025)

Abstract
We develop a denotational model for probabilistic and concurrent imperative programs, a class of programs with standard control flow via conditionals and while-loops, as well as probabilistic actions and parallel composition. Whereas semantics for concurrent or randomized programs in isolation is well studied, their combination has not been thoroughly explored and presents unique challenges. The crux of the problem is that interactions between control flow, probabilistic actions, and concurrent execution cannot be captured by straightforward generalizations of prior work on pomsets and convex languages, prominent models for those effects, individually. Our model has good domain theoretic properties, important for semantics of unbounded loops. We also prove two adequacy theorems, showing that the model subsumes typical powerdomain semantics for concurrency and convex powerdomain semantics for probabilistic nondeterminism.
Cite as

Noam Zilberstein, Daniele Gorla, and Alexandra Silva. Denotational Semantics for Probabilistic and Concurrent Programs. In 36th International Conference on Concurrency Theory (CONCUR 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 348, pp. 39:1-39:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{zilberstein_et_al:LIPIcs.CONCUR.2025.39,
  author =	{Zilberstein, Noam and Gorla, Daniele and Silva, Alexandra},
  title =	{{Denotational Semantics for Probabilistic and Concurrent Programs}},
  booktitle =	{36th International Conference on Concurrency Theory (CONCUR 2025)},
  pages =	{39:1--39:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-389-8},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{348},
  editor =	{Bouyer, Patricia and van de Pol, Jaco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2025.39},
  URN =		{urn:nbn:de:0030-drops-239890},
  doi =		{10.4230/LIPIcs.CONCUR.2025.39},
  annote =	{Keywords: Denotational Semantics, Pomsets, Concurrency, Convex Powerset}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2024.1
A Sound Type System for Secure Currency Flow

Authors: Luca Aceto, Daniele Gorla, and Stian Lybech

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
In this paper we focus on TinySol, a minimal calculus for Solidity smart contracts, introduced by Bartoletti et al. We start by rephrasing its syntax (to emphasise its object-oriented flavour) and give a new big-step operational semantics. We then use it to define two security properties, namely call integrity and noninterference. These two properties have some similarities in their definition, in that they both require that some part of a program is not influenced by the other part. However, we show that the two properties are actually incomparable. Nevertheless, we provide a type system for noninterference and show that well-typed programs satisfy call integrity as well; hence, programs that are accepted by our type system satisfy both properties. We finally discuss the practical usability of the type system and its limitations by means of some simple examples.
Cite as

Luca Aceto, Daniele Gorla, and Stian Lybech. A Sound Type System for Secure Currency Flow. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 1:1-1:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{aceto_et_al:LIPIcs.ECOOP.2024.1,
  author =	{Aceto, Luca and Gorla, Daniele and Lybech, Stian},
  title =	{{A Sound Type System for Secure Currency Flow}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{1:1--1:27},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2024.1},
  URN =		{urn:nbn:de:0030-drops-208508},
  doi =		{10.4230/LIPIcs.ECOOP.2024.1},
  annote =	{Keywords: smart contracts, call integrity, noninterference, type system}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.4
Centralized vs Decentralized Monitors for Hyperproperties

Authors: Luca Aceto, Antonis Achilleos, Elli Anastasiadi, Adrian Francalanza, Daniele Gorla, and Jana Wagemaker

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
This paper focuses on the runtime verification of hyperproperties expressed in Hyper-recHML, an expressive yet simple logic for describing properties of sets of traces. To this end, we consider a simple language of monitors that observe sets of system executions and report verdicts w.r.t. a given Hyper-recHML formula. We first employ a unique omniscient monitor that centrally observes all system traces. Since centralised monitors are not ideal for distributed settings, we also provide a language for decentralized monitors, where each trace has a dedicated monitor; these monitors yield a unique verdict by communicating their observations to one another. For both the centralized and the decentralized settings, we provide a synthesis procedure that, given a formula, yields a monitor that is correct (i.e., sound and violation complete). A key step in proving the correctness of the synthesis for decentralized monitors is a result showing that, for each formula, the synthesized centralized monitor and its corresponding decentralized one are weakly bisimilar for a suitable notion of weak bisimulation.
Cite as

Luca Aceto, Antonis Achilleos, Elli Anastasiadi, Adrian Francalanza, Daniele Gorla, and Jana Wagemaker. Centralized vs Decentralized Monitors for Hyperproperties. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 4:1-4:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{aceto_et_al:LIPIcs.CONCUR.2024.4,
  author =	{Aceto, Luca and Achilleos, Antonis and Anastasiadi, Elli and Francalanza, Adrian and Gorla, Daniele and Wagemaker, Jana},
  title =	{{Centralized vs Decentralized Monitors for Hyperproperties}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{4:1--4:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.4},
  URN =		{urn:nbn:de:0030-drops-207763},
  doi =		{10.4230/LIPIcs.CONCUR.2024.4},
  annote =	{Keywords: Runtime Verification, hyperlogics, decentralization}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2021.19
Algebra and Coalgebra of Stream Products

Authors: Michele Boreale and Daniele Gorla

Published in: LIPIcs, Volume 203, 32nd International Conference on Concurrency Theory (CONCUR 2021)

Abstract
We study connections among polynomials, differential equations and streams over a field 𝕂, in terms of algebra and coalgebra. We first introduce the class of (F,G)-products on streams, those where the stream derivative of a product can be expressed as a polynomial of the streams themselves and their derivatives. Our first result is that, for every (F,G)-product, there is a canonical way to construct a transition function on polynomials such that the induced unique final coalgebra morphism from polynomials into streams is the (unique) 𝕂-algebra homomorphism - and vice-versa. This implies one can reason algebraically on streams, via their polynomial representation. We apply this result to obtain an algebraic-geometric decision algorithm for polynomial stream equivalence, for an underlying generic (F,G)-product. As an example of reasoning on streams, we focus on specific products (convolution, shuffle, Hadamard) and show how to obtain closed forms of algebraic generating functions of combinatorial sequences, as well as solutions of nonlinear ordinary differential equations.
Cite as

Michele Boreale and Daniele Gorla. Algebra and Coalgebra of Stream Products. In 32nd International Conference on Concurrency Theory (CONCUR 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 203, pp. 19:1-19:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{boreale_et_al:LIPIcs.CONCUR.2021.19,
  author =	{Boreale, Michele and Gorla, Daniele},
  title =	{{Algebra and Coalgebra of Stream Products}},
  booktitle =	{32nd International Conference on Concurrency Theory (CONCUR 2021)},
  pages =	{19:1--19:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-203-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{203},
  editor =	{Haddad, Serge and Varacca, Daniele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2021.19},
  URN =		{urn:nbn:de:0030-drops-143969},
  doi =		{10.4230/LIPIcs.CONCUR.2021.19},
  annote =	{Keywords: Streams, coalgebras, polynomials, differential equations}
}
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