5 Search Results for "Sjöberg, Vilhelm"

Document
DOI: 10.4230/LIPIcs.CSL.2026.37
Towards the Type Safety of Pure Subtype Systems

Authors: Valentin Pasquale and Álvaro García-Pérez

Published in: LIPIcs, Volume 363, 34th EACSL Annual Conference on Computer Science Logic (CSL 2026)

Abstract
Hutchins' Pure Subtype Systems (PSS) offer a unified framework for types and terms, promising significant advancements in language design for features like dependent types and higher-order subtyping. However, the theory has been hampered by a critical gap: a proof of type safety has remained an open problem for over a decade. The original attempt to prove this property relied on the conjectured commutativity of two fundamental reduction relations, equivalence and subtyping. Proving transitivity elimination, however, requires this commutativity, a property that is notoriously difficult to establish for higher-order subtyping systems. In this paper, we address this issue by introducing Machine-Based PSS (MPSS), a novel reformulation of the original system. MPSS integrates a continuation stack mechanism, reminiscent of the Krivine Abstract Machine, to keep track of arguments that are passed during function application, enabling more fine-grained reductions. This architectural change exposes crucial intermediate reduction steps that were absent in the original PSS. The primary contribution of our work is a direct proof that the equivalence and subtyping reductions in MPSS commute. This result formally establishes transitivity elimination, which is the cornerstone of the inversion lemma required for type safety. We conclude by outlining a pathway from our foundational result to a complete, type-safe system, thereby paving the way for the practical realization of PSS-based languages.
Cite as

Valentin Pasquale and Álvaro García-Pérez. Towards the Type Safety of Pure Subtype Systems. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 37:1-37:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{pasquale_et_al:LIPIcs.CSL.2026.37,
  author =	{Pasquale, Valentin and Garc{\'\i}a-P\'{e}rez, \'{A}lvaro},
  title =	{{Towards the Type Safety of Pure Subtype Systems}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{37:1--37:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-411-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{363},
  editor =	{Guerrini, Stefano and K\"{o}nig, Barbara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.37},
  URN =		{urn:nbn:de:0030-drops-254626},
  doi =		{10.4230/LIPIcs.CSL.2026.37},
  annote =	{Keywords: Lambda calculus, Pure subtype systems, Dependent types, Higher-order subtyping, Type safety}
}
Document
DOI: 10.4230/OASIcs.FMBC.2025.3
Formal Verification in Solidity and Move: Insights from a Comparative Analysis

Authors: Massimo Bartoletti, Silvia Crafa, and Enrico Lipparini

Published in: OASIcs, Volume 129, 6th International Workshop on Formal Methods for Blockchains (FMBC 2025)

Abstract
Formal verification plays a crucial role in making smart contracts safer, being able to find bugs or to guarantee their absence, as well as checking whether the business logic is correctly implemented. For Solidity, even though there already exist several mature verification tools, the semantical quirks of the language can make verification quite hard in practice. Move, on the other hand, has been designed with security and verification in mind, and it has been accompanied since its early stages by a formal verification tool, the Move Prover. In this paper, we investigate through a comparative analysis: 1) how the different designs of the two contract languages impact verification, and 2) what is the state-of-the-art of verification tools for the two languages, and how do they compare on three paradigmatic use cases. Our investigation is supported by an open dataset of verification tasks performed in Certora and in the Aptos Move Prover.
Cite as

Massimo Bartoletti, Silvia Crafa, and Enrico Lipparini. Formal Verification in Solidity and Move: Insights from a Comparative Analysis. In 6th International Workshop on Formal Methods for Blockchains (FMBC 2025). Open Access Series in Informatics (OASIcs), Volume 129, pp. 3:1-3:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bartoletti_et_al:OASIcs.FMBC.2025.3,
  author =	{Bartoletti, Massimo and Crafa, Silvia and Lipparini, Enrico},
  title =	{{Formal Verification in Solidity and Move: Insights from a Comparative Analysis}},
  booktitle =	{6th International Workshop on Formal Methods for Blockchains (FMBC 2025)},
  pages =	{3:1--3:18},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-371-3},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{129},
  editor =	{Marmsoler, Diego and Xu, Meng},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2025.3},
  URN =		{urn:nbn:de:0030-drops-230302},
  doi =		{10.4230/OASIcs.FMBC.2025.3},
  annote =	{Keywords: Smart contracts, Solidity, Move, Verification, Blockchain}
}
Document
DOI: 10.4230/OASIcs.FMBC.2025.8
Formal Verification of a Fail-Safe Cross-Chain Bridge

Authors: Filip Marić, Bernhard Scholz, and Pavle Subotić

Published in: OASIcs, Volume 129, 6th International Workshop on Formal Methods for Blockchains (FMBC 2025)

Abstract
Cross-chain bridges are financial services that interconnect blockchains. High monetary values flow through these bridges, and their security must be safeguarded. However, designing real-world cross-chain bridges is a difficult endeavor. Due to blockchain’s closed-world nature, tokens cannot be transferred from a sender to a receiver chain; on the contrary, they need complex logic that maintains an equilibrium on both chains, even if either the chains or the bridge fail. This paper formally verifies a model of a novel fail-safe cross-chain bridge to ensure correctness. We define formal requirements and prove the bridge is safe using the Isabelle/HOL proof assistant.
Cite as

Filip Marić, Bernhard Scholz, and Pavle Subotić. Formal Verification of a Fail-Safe Cross-Chain Bridge. In 6th International Workshop on Formal Methods for Blockchains (FMBC 2025). Open Access Series in Informatics (OASIcs), Volume 129, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{maric_et_al:OASIcs.FMBC.2025.8,
  author =	{Mari\'{c}, Filip and Scholz, Bernhard and Suboti\'{c}, Pavle},
  title =	{{Formal Verification of a Fail-Safe Cross-Chain Bridge}},
  booktitle =	{6th International Workshop on Formal Methods for Blockchains (FMBC 2025)},
  pages =	{8:1--8:18},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-371-3},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{129},
  editor =	{Marmsoler, Diego and Xu, Meng},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2025.8},
  URN =		{urn:nbn:de:0030-drops-230342},
  doi =		{10.4230/OASIcs.FMBC.2025.8},
  annote =	{Keywords: Cross-Chain Bridge, Formal Verification, Logic, Security}
}
Document
DOI: 10.4230/OASIcs.FMBC.2021.1
Towards Verified Price Oracles for Decentralized Exchange Protocols

Authors: Kinnari Dave, Vilhelm Sjöberg, and Xinyuan Sun

Published in: OASIcs, Volume 95, 3rd International Workshop on Formal Methods for Blockchains (FMBC 2021)

Abstract
Various smart contracts have been designed and deployed on blockchain platforms to enable cryptocurrency trading, leading to an ever expanding user base of decentralized exchange platforms (DEXs). Automated Market Maker contracts enable token exchange without the need of third party book-keeping. These contracts also serve as price oracles for other contracts, by using a mathematical formula to calculate token exchange rates based on token reserves. However, the price oracle mechanism is vulnerable to attacks both from programming errors and from mistakes in the financial model, and so far their complexity makes it difficult to formally verify them. We present a verified AMM contract and validate its financial model by proving a theorem about a lower bound on the cost of manipulation of the token prices to the attacker. The contract is implemented using the DeepSEA system, which ensures that the theorem applies to the actual EVM bytecode of the contract. This theorem could be used as proof of correctness for other contracts using the AMM, so this is a step towards a verified DeFi landscape.
Cite as

Kinnari Dave, Vilhelm Sjöberg, and Xinyuan Sun. Towards Verified Price Oracles for Decentralized Exchange Protocols. In 3rd International Workshop on Formal Methods for Blockchains (FMBC 2021). Open Access Series in Informatics (OASIcs), Volume 95, pp. 1:1-1:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{dave_et_al:OASIcs.FMBC.2021.1,
  author =	{Dave, Kinnari and Sj\"{o}berg, Vilhelm and Sun, Xinyuan},
  title =	{{Towards Verified Price Oracles for Decentralized Exchange Protocols}},
  booktitle =	{3rd International Workshop on Formal Methods for Blockchains (FMBC 2021)},
  pages =	{1:1--1:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-209-9},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{95},
  editor =	{Bernardo, Bruno and Marmsoler, Diego},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2021.1},
  URN =		{urn:nbn:de:0030-drops-154254},
  doi =		{10.4230/OASIcs.FMBC.2021.1},
  annote =	{Keywords: Smart Contract Verification, Interactive Theorem Proving, Blockchain, Decentralized Finance}
}
Document
Short Paper
DOI: 10.4230/OASIcs.FMBC.2021.3
Using Coq to Enforce the Checks-Effects-Interactions Pattern in DeepSEA Smart Contracts (Short Paper)

Authors: Daniel Britten, Vilhelm Sjöberg, and Steve Reeves

Published in: OASIcs, Volume 95, 3rd International Workshop on Formal Methods for Blockchains (FMBC 2021)

Abstract
Using the DeepSEA system for smart contract proofs, this paper investigates how to use the Coq theorem prover to enforce that smart contracts follow the Checks-Effects-Interactions Pattern. This pattern is widely understood to mitigate the risks associated with reentrancy. The infamous "The DAO" exploit is an example of the risks of not following the Checks-Effects-Interactions Pattern. It resulted in the loss of over 50 million USD and involved reentrancy - the exploit used would not have been possible if the Checks-Effects-Interactions Pattern had been followed. Remix IDE, for example, already has a tool to check that the Checks-Effects-Interactions Pattern has been followed as part of the Solidity Static Analysis module which is available as a plugin. However, aside from simply replicating the Remix IDE feature, implementing a Checks-Effects-Interactions Pattern checker in the proof assistant Coq also allows us to use the proofs, which are generated in the process, in other proofs related to the smart contract. As an example of this, we will demonstrate an idea for how the modelling of Ether transfer can be simplified by using automatically generated proofs of the property that each smart contract function will call the Ether transfer method at most once (excluding any calls related to invoking other smart contracts). This property is a consequence of following a strict version of the Checks-Effects-Interactions Pattern as given in this paper.
Cite as

Daniel Britten, Vilhelm Sjöberg, and Steve Reeves. Using Coq to Enforce the Checks-Effects-Interactions Pattern in DeepSEA Smart Contracts (Short Paper). In 3rd International Workshop on Formal Methods for Blockchains (FMBC 2021). Open Access Series in Informatics (OASIcs), Volume 95, pp. 3:1-3:8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{britten_et_al:OASIcs.FMBC.2021.3,
  author =	{Britten, Daniel and Sj\"{o}berg, Vilhelm and Reeves, Steve},
  title =	{{Using Coq to Enforce the Checks-Effects-Interactions Pattern in DeepSEA Smart Contracts}},
  booktitle =	{3rd International Workshop on Formal Methods for Blockchains (FMBC 2021)},
  pages =	{3:1--3:8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-209-9},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{95},
  editor =	{Bernardo, Bruno and Marmsoler, Diego},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2021.3},
  URN =		{urn:nbn:de:0030-drops-154272},
  doi =		{10.4230/OASIcs.FMBC.2021.3},
  annote =	{Keywords: smart contracts, formal methods, blockchain}
}
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