6 Search Results for "Vasconcelos, Pedro"

Document
DOI: 10.4230/LIPIcs.AFT.2025.32
4-Swap: Achieving Grief-Free and Bribery-Safe Atomic Swaps Using Four Transactions

Authors: Kirti Singh, Vinay J. Ribeiro, and Susmita Mandal

Published in: LIPIcs, Volume 354, 7th Conference on Advances in Financial Technologies (AFT 2025)

Abstract
Cross-chain asset exchange is crucial for blockchain interoperability. Existing solutions rely on trusted third parties and risk asset loss, or use decentralized alternatives like atomic swaps, which suffer from grief attacks. Griefing occurs when a party prematurely exits, locking the counterparty’s assets until a timelock expires. Hedged Atomic Swaps mitigate griefing by introducing a penalty premium; however, they increase the number of transactions from four (as in Tier Nolan’s swap) to six, which in turn introduces new griefing risks. Grief-Free (GF) Swap reduces this to five transactions by consolidating assets and premiums on a single chain. However, no existing protocol achieves grief-free asset exchange in just four transactions. This paper presents 4-Swap, the first cross-chain atomic swap protocol that is both grief-free and bribery-safe, while completing asset exchange in just four transactions. By combining the griefing premium and principal into a single transaction per chain, 4-Swap reduces on-chain transactions, leading to faster execution compared to previous grief-free solutions. It is fully compatible with Bitcoin and operates without the need for any new opcodes. A game-theoretic analysis shows that rational participants have no incentive to deviate from the protocol, ensuring robust compliance and security.
Cite as

Kirti Singh, Vinay J. Ribeiro, and Susmita Mandal. 4-Swap: Achieving Grief-Free and Bribery-Safe Atomic Swaps Using Four Transactions. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 32:1-32:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{singh_et_al:LIPIcs.AFT.2025.32,
  author =	{Singh, Kirti and Ribeiro, Vinay J. and Mandal, Susmita},
  title =	{{4-Swap: Achieving Grief-Free and Bribery-Safe Atomic Swaps Using Four Transactions}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{32:1--32:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-400-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{354},
  editor =	{Avarikioti, Zeta and Christin, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2025.32},
  URN =		{urn:nbn:de:0030-drops-247514},
  doi =		{10.4230/LIPIcs.AFT.2025.32},
  annote =	{Keywords: Atomic Swaps, Griefing, Bribery, HTLC}
}
Document
DOI: 10.4230/LIPIcs.AFT.2025.31
Trustless Bridges via Random Sampling Light Clients

Authors: Bhargav Nagaraja Bhatt, Fatemeh Shirazi, and Alistair Stewart

Published in: LIPIcs, Volume 354, 7th Conference on Advances in Financial Technologies (AFT 2025)

Abstract
The increasing number of blockchain projects introduced annually has led to a pressing need for secure and efficient interoperability solutions. Currently, the lack of such solutions forces end-users to rely on centralized intermediaries, contradicting the core principle of decentralization and trust minimization in blockchain technology. We propose a decentralized and efficient interoperability solution (aka Bridge Protocol) that operates without additional trust assumptions, relying solely on the Byzantine Fault Tolerance (BFT) properties of the two chains being connected. In particular, relayers (actors that exchange messages between networks) are permissionless and decentralized, hence eliminating any single point of failure. We introduce Random Sampling, a novel technique for on-chain light clients to efficiently follow the history of PoS blockchains by reducing the signature verifications required. Here, the randomness is drawn on-chain, for example, using Ethereum’s RANDAO. We analyze the security of the bridge from a crypto- economic perspective and provide a framework to derive the security parameters. This includes handling subtle concurrency issues and randomness bias in strawman designs. While the protocol is applicable to various PoS chains, we demonstrate the protocol’s practical feasibility by showcasing an instantiated bridge between Polkadot and Ethereum (currently deployed), and discuss some practical security challenges. Furthermore, we evaluate the efficiency of our on-chain light client verifier (implemented as an Ethereum smart contract) against SNARK-based approaches, demonstrating significantly lower gas costs for signature verification - even for validator sets up to 10⁶.
Cite as

Bhargav Nagaraja Bhatt, Fatemeh Shirazi, and Alistair Stewart. Trustless Bridges via Random Sampling Light Clients. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 31:1-31:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bhatt_et_al:LIPIcs.AFT.2025.31,
  author =	{Bhatt, Bhargav Nagaraja and Shirazi, Fatemeh and Stewart, Alistair},
  title =	{{Trustless Bridges via Random Sampling Light Clients}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{31:1--31:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-400-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{354},
  editor =	{Avarikioti, Zeta and Christin, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2025.31},
  URN =		{urn:nbn:de:0030-drops-247503},
  doi =		{10.4230/LIPIcs.AFT.2025.31},
  annote =	{Keywords: PoS Blockchains, Trustless Bridges, Light Clients, Decentralised Relayers, RANDAO Bias}
}
Document
DOI: 10.4230/OASIcs.ICPEC.2025.1
Exploring Mutation Testing for Teaching Introductory Programming

Authors: Pedro Vasconcelos

Published in: OASIcs, Volume 133, 6th International Computer Programming Education Conference (ICPEC 2025)

Abstract
This paper proposes the use of introductory programming assignments based on mutation testing where students are asked to write tests rather than code. We believe such exercises can be used to teach code reading skills before students could write the corresponding programs on their own. Furthermore, feedback for such exercises can be automatically generated using testing tools. We have extended an existing web-based system for programming exercises with such mutation testing assignments and show some example use cases. This is on-going work that has yet to be validated in the classroom.
Cite as

Pedro Vasconcelos. Exploring Mutation Testing for Teaching Introductory Programming. In 6th International Computer Programming Education Conference (ICPEC 2025). Open Access Series in Informatics (OASIcs), Volume 133, pp. 1:1-1:8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{vasconcelos:OASIcs.ICPEC.2025.1,
  author =	{Vasconcelos, Pedro},
  title =	{{Exploring Mutation Testing for Teaching Introductory Programming}},
  booktitle =	{6th International Computer Programming Education Conference (ICPEC 2025)},
  pages =	{1:1--1:8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-393-5},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{133},
  editor =	{Queir\'{o}s, Ricardo and Pinto, M\'{a}rio and Portela, Filipe and Sim\~{o}es, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ICPEC.2025.1},
  URN =		{urn:nbn:de:0030-drops-240319},
  doi =		{10.4230/OASIcs.ICPEC.2025.1},
  annote =	{Keywords: mutation testing, programming education}
}
Document
DOI: 10.4230/OASIcs.ICPEC.2024.5
Kumon-Inspired Approach to Teaching Programming Fundamentals

Authors: Ivone Amorim, Pedro Baltazar Vasconcelos, and João Pedro Pedroso

Published in: OASIcs, Volume 122, 5th International Computer Programming Education Conference (ICPEC 2024)

Abstract
Integration of introductory programming into higher education programs beyond computer science has lead to an increase in the failure and drop out rates of programming courses. In this context, programming instructors have explored new methodologies by introducing dynamic elements in the teaching-learning process, such as automatic code evaluation systems and gamification. Even though these methods have shown to be successful in improving students' engagement, they do not address all the existing problems and new strategies should be explored. In this work, we propose a new approach that combines the strengths of the Kumon method for personalized learning and progressive skill acquisition with the ability of online judge systems to provide automated assessment and immediate feedback. This approach has been used in teaching Programming I to students in several bachelor degrees and led to a 10% increase in exam approval rates compared to the baseline editions in which our Kumon-inspired methodology was not implemented.
Cite as

Ivone Amorim, Pedro Baltazar Vasconcelos, and João Pedro Pedroso. Kumon-Inspired Approach to Teaching Programming Fundamentals. In 5th International Computer Programming Education Conference (ICPEC 2024). Open Access Series in Informatics (OASIcs), Volume 122, pp. 5:1-5:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{amorim_et_al:OASIcs.ICPEC.2024.5,
  author =	{Amorim, Ivone and Vasconcelos, Pedro Baltazar and Pedroso, Jo\~{a}o Pedro},
  title =	{{Kumon-Inspired Approach to Teaching Programming Fundamentals}},
  booktitle =	{5th International Computer Programming Education Conference (ICPEC 2024)},
  pages =	{5:1--5:13},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-347-8},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{122},
  editor =	{Santos, Andr\'{e} L. and Pinto-Albuquerque, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ICPEC.2024.5},
  URN =		{urn:nbn:de:0030-drops-209749},
  doi =		{10.4230/OASIcs.ICPEC.2024.5},
  annote =	{Keywords: Programming teaching, Programming education, Kumon method, Progressive learning, Online judge system}
}
Document
DOI: 10.4230/OASIcs.ICPEC.2023.12
Haskelite: A Step-By-Step Interpreter for Teaching Functional Programming

Authors: Pedro Vasconcelos

Published in: OASIcs, Volume 112, 4th International Computer Programming Education Conference (ICPEC 2023)

Abstract
This paper describes Haskelite, a step-by-step interpreter for a small subset of Haskell. Haskelite is designed to help teach fundamental concepts of functional programming, namely: evaluation by rewriting; definition of functions using pattern-matching; recursion; higher-order functions; and on-demand evaluation. The interpreter is implemented in Elm and compiled to JavaScript, so it runs on the browser and requires no installation. This is on-going work and has yet to be fully evaluated; we present some initial experience in the classroom and highlight some points for improvement.
Cite as

Pedro Vasconcelos. Haskelite: A Step-By-Step Interpreter for Teaching Functional Programming. In 4th International Computer Programming Education Conference (ICPEC 2023). Open Access Series in Informatics (OASIcs), Volume 112, pp. 12:1-12:8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{vasconcelos:OASIcs.ICPEC.2023.12,
  author =	{Vasconcelos, Pedro},
  title =	{{Haskelite: A Step-By-Step Interpreter for Teaching Functional Programming}},
  booktitle =	{4th International Computer Programming Education Conference (ICPEC 2023)},
  pages =	{12:1--12:8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-290-7},
  ISSN =	{2190-6807},
  year =	{2023},
  volume =	{112},
  editor =	{Peixoto de Queir\'{o}s, Ricardo Alexandre and Teixeira Pinto, M\'{a}rio Paulo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ICPEC.2023.12},
  URN =		{urn:nbn:de:0030-drops-185080},
  doi =		{10.4230/OASIcs.ICPEC.2023.12},
  annote =	{Keywords: Functional programming, Step-by-step evaluators, Web applications}
}
Document
DOI: 10.4230/OASIcs.ICPEC.2020.28
Using Property-Based Testing to Generate Feedback for C Programming Exercises

Authors: Pedro Vasconcelos and Rita P. Ribeiro

Published in: OASIcs, Volume 81, First International Computer Programming Education Conference (ICPEC 2020)

Abstract
This paper reports on the use of property-based testing for providing feedback to C programming exercises. Test cases are generated automatically from properties specified in a test script; this not only makes it possible to conduct many tests (thus potentially find more mistakes), but also allows simplifying failed tests cases automatically. We present some experimental validation gathered for an introductory C programming course during the fall semester of 2018 that show significant positive correlations between getting feedback during the semester and the student’s results in the final exam. We also discuss some limitations regarding feedback for undefined behaviors in the C language.
Cite as

Pedro Vasconcelos and Rita P. Ribeiro. Using Property-Based Testing to Generate Feedback for C Programming Exercises. In First International Computer Programming Education Conference (ICPEC 2020). Open Access Series in Informatics (OASIcs), Volume 81, pp. 28:1-28:10, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{vasconcelos_et_al:OASIcs.ICPEC.2020.28,
  author =	{Vasconcelos, Pedro and Ribeiro, Rita P.},
  title =	{{Using Property-Based Testing to Generate Feedback for C Programming Exercises}},
  booktitle =	{First International Computer Programming Education Conference (ICPEC 2020)},
  pages =	{28:1--28:10},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-153-5},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{81},
  editor =	{Queir\'{o}s, Ricardo and Portela, Filipe and Pinto, M\'{a}rio and Sim\~{o}es, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ICPEC.2020.28},
  URN =		{urn:nbn:de:0030-drops-123159},
  doi =		{10.4230/OASIcs.ICPEC.2020.28},
  annote =	{Keywords: property-based testing, C language, Haskell language, teaching programming}
}
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