Published Papers
9 published papers

Papers published in the scope of my Ph.D thesis, but also stemming from other collaborations.

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Thesis

My M.Sc. thesis

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Talks

Presentations given at a venue for which there is not a presented paper.

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Events

Conferences/Workshops attended in the scope of my academic work

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Service to the Community

Paper reviews

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Others
Technical Reports, ...

Other documents tailored in the context of my research or other collaborations

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Published Papers

With a brief commentary

Martin Hargreaves, Thomas Hardjono, Rafael Belchior

Technical Report IETF, 2021

This memo describes the Open Digital Asset Protocol (ODAP). ODAP is an asset transfer protocol that operates between two gateway devices. The protocol includes a description of virtual or digital assets held on distributed ledgers in an open and interoperable format, a session negotiation part and message passing flows between gateways connecting disparate distributed ledger technologies (DLTs).

Rafael Belchior, André Vasconcelos, Miguel Correia and Thomas Hardjono

Conference to appear 2021

This memo describes crash recovery mechanisms for the Open Digital Asset Protocol (ODAP). The memo presents ODAP-2PC, a protocol assures that gateways running ODAP are crash fault-tolerant, meaning that the atomicity of asset transfers are assured even if gateways crash. This protocol includes the description of the messaging and logging flows necessary for gateways to keep track of current state, the crash-recovery protocol, and a rollback mechanism.

Sara Ghaemi, Sara Rouhani, Rafael Belchior, Rui Cruz, Hamzeh Khazaei and Petr Musilek

Conference To appear, 2021

This paper proposes a novel blockchain interoperability solution for permissioned blockchains based on the publish/subscribe architecture - the outcome of a Hyperledger Summer Internship.

Rafael Belchior, Miguel Correia and Thomas Hardjono

Technical Report IETF, 2020

This memo describes crash recovery mechanisms for the Open Digital Asset Protocol (ODAP). The memo presents ODAP-2PC, a protocol assures that gateways running ODAP are crash fault-tolerant, meaning that the atomicity of asset transfers are assured even if gateways crash. This protocol includes the description of the messaging and logging flows necessary for gateways to keep track of current state, the crash-recovery protocol, and a rollback mechanism.

Rafael Belchior, Sérgio Guerreiro, André Vasconcelos, and Miguel Correia

Journal Under Review at BPM Journal. Preliminary version available at arXiv

This study gives an overview of the business process view integration research area. Rooted on database schema integration, business process view integration is needed to consolidate different versions of the same business process. It turns out that lessons from this area are directly applicable to blockchain, because blockchain supports different views on the same data, contrarily to common knowledge.

Rafael Belchior, Benedikt Putz, Guenther Pernul, Miguel Correia, André Vasconcelos, Sérgio Guerreiro

Workshop IEEE 3rd International Workshop on Blockchain Systems and Applications

This paper implements efforts with a colleague and friend from Germany, Benedikt and his advisor, Guenther. I've got to know Benedikt from his incredibly talented work, A secure and auditable logging infrastructure based on a permissioned blockchain. After Benedikt helped me with my own paper, Towards Secure, Decentralized, and Automatic Audits With Blockchain, we started cooperating. We are both fascinated on how one can use the self sovereign identity paradigm to achieve privacy-preserving access control processes. This was then our first effort understanding decentralized identifiers, verifiable credentials, and identity-centric blockchains. We design an integration between blockchains and centralized access control mechanisms encoding access control policies into verifiable presentations. This paves the way for more privacy preserving access control enterprise scenarios.

A poster presented on Tecnico Lisboa PhD Open Days is available, as well as its presentation, in the form of a video poster.

Rafael Belchior, André Vasconcelos, Sérgio Guerreiro, Miguel Correia

Journal Under Review at ACM CSUR. Preliminary version available at arXiv

This survey depicts the past and current state of blockchain interoperability, presenting and categorizing existing solutions. It discusses in detail what is blockchain interoperability, the proposed architectures, use cases, challenges, and future research directions. What I consider special about this survey is that we contacted dozens of people asking feedback on their solutions. It ensured us to have updated information, in a research area set up by obsolete whitepapers. This is the first paper I wrote that I consider a very good paper - It took around 6 months to write, and was reviewed by several colleagues.

Sara Rouhani, Rafael Belchior, Rui Cruz, Ralph Deters

Journal World Wide Web 2021

This paper was the result of a collaboration with Prof. Rui Cruz, an Assistant Professor from Técnico, and Sara Rouhani, a PhD candidate at the University of Saskatchewan. On the context of a Hyperledger Summer Internship, we implemented a blockchain-based access control system based on Hyperledger Fabric, and explored its capabilities and limitations. It turns out that decentralized access control is quite feasible, we believe even in cross-organizational settings. Looking back, I'm glad to work with such I took the courage to challenge Prof. Rui to go forward with this project.

Rafael Belchior, Miguel Correia, and André Vasconcelos

Conference ECIS '20: European Conference on Information Systems, 2020

I consider the second paper I wrote to be a very notorious improvement compared to the first. In this paper, we extended JusticeChain to support audit processes - by enconding dummy audit rules into smart contracts. This technique caught the interest of the reviewers, as it could be easily integrated with real audits, given that the audit rules satisfy the GDPR.

Rafael Belchior, Miguel Correia, and André Vasconcelos

Conference CoopIS 2019: 27th International Conference on COOPERATIVE INFORMATION SYSTEMS, 2019

This was the first paper I wrote, in the context of my MSc degree - and my first direct contact with academia. Although very drafty, it exposes the long term effort collaborating with the Portuguese public sector. I learned how to ally the academic thinking with the practical effort of developing a system to be production ready. The experience on the academic conference was very motivating as well.

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Talks

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Theses

  • 1.JusticeChain: Using Blockchain To Protect Justice Data

    Rafael Belchior

    MSc Thesis Instituto Superior Técnico, December 2019

    Corruption is a major problem worldwide. It comes in the form of dishonesty or criminal offense when parties entrusted with a position of authority, acquire illicit benefit – affecting all areas of society.

    It then does not come with a surprise that corruption is present at governments, given a variety of reasons: technological limitations regarding traceability, lack of transparency, lack of auditability, and lack of accountability. This causes distrust among stakeholders within the government, causing prejudice to possible synergies that can raise efficiency and improve the status quo.

    We are then living in a world where decisions from governments are taken with distrust, and accountability is not well-tracked. At the Portuguese justice, this lack of trust exists. Justice is one of the areas where the distrust is most notable. Stakeholders from the judicial power (judges, court clerk, probation officers) utilize an information system managed by the political power (IGFEJ, responding to the government), called Citius. Citius allows to expedite judicial court processes, and it is considered a basilar information system for the good functioning of our country. As an example, when Citius was stopped, the courts were not functioning for 44 days.

    As stakeholders are independent and may have conflicting interests, questions may arise: can we, as judges, trust and empower information systems managed by the government? Can we trust that government parties are not accessing the data we are generating? Can we believe that a database administrator with root permissions did not access data and then deleted his or her traces? As the government, how can we assure stakeholders from the judicial power that their information is only accessed with due permissions, in a transparent and traceable way?

    JusticeChain is the outcome of a master thesis, attempting to provide a virtuous solution to these problems: it assures all parties that critical information can only be accessed when there is consent from the majority of the stakeholders. The information, and their access history, are protected in an immutable way, providing a solid basis for audits and accountability. These technological advances are made possible due to the emerging of enterprise blockchain technologies, that leverage a shared database, whereby any updates are only possible if the majority of their users agree on the updates. This leads to the creation of a global, shared state, which all parties can trust it was not tampered with.

    As JusticeChain is modular and extensible, it can tackle other applications. For instance, collaborations across governmental organizations managed by several stakeholders who do not trust each other (criminal records, public funds management, online voting, higher education certification) can benefit from JusticeChain: it can enforce its immutability, traceability, secure and distributed access control, and transparency.

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Students

  • I advise master students, mostly on topics related to my PhD thesis. If you are interested in these topics, please contact me.

    Luís Abrunhosa: Migrating Smart Contracts Across Heterogeneous Blockchains, co-advised with André Vasconcelos and João Ferreira

    Catarina Pedreira: Trustable Blockchain Interoperability: Incentivizing Public Escrow Parties, co-advised with André Vasconcelos and Miguel Matos.

    José Lino: Distributed, Trustless, Service Providing with a Sharded-enabled Blockchain, co-advised with André Vasconcelos.
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Events Attended

International Symposium on Foundations and Applications of Blockchain '21
Virtual Event, May 2021

Attending International Symposium on Foundations and Applications of Blockchain.

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CROSS '21
Virtual Event, March 2021

Presenting Hyperledger Cactus at Crosschain Workshop 2021

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ICBC '21
Virtual Event, May 2021

Attending IEEE International Conference on Blockchain and Cryptocurrency

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TrustCom '20
Virtual Event, December 2020

Presenting the paper SSIBAC at 19th IEEE International Conference on Trust, Security and Privacy in Computing and Communications (IEEE TrustCom 2020).

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CROSS '21
Virtual Event, March 2021

Presenting Hyperledger Cactus at Crosschain Workshop 2021

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ICBC '21
Virtual Event, May 2021

Attending IEEE International Conference on Blockchain and Cryptocurrency

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ICDCS '20
Virtual Event, November 2020

Attending 2020 IEEE 40th International Conference on Distributed Computing Systems (ICDCS).

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ACM CCS '20
Virtual Event, November 2020

Attending 2020 ACM SIGSAC Conference on Computer and Communications Security.

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IETF 109
Virtual Event, November 2020

Attending IETF 109 in the context of ODAP and ODAP-2PC.

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COOPIS '19
October 2019, Rhodes, Greece

Presenting the paper Justicechain at 27th International Conference on COOPERATIVE INFORMATION SYSTEMS.

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ECIS '20
Marrakech, Morocco (Virtual Event), June 2020

Presenting Towards Secure, Decentralized, and Automatic Audits with Blockchain at European Conference on Information Systems.

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PhD Open Days '20
Lisboa, Portugal (Virtual Event), October 2020

- Presenting a Poster on SSIBAC at PhD Open Days 2020, Técnico Lisboa, Lisboa, Portugal (Virtual Event), October 2020

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Service to the Community as Reviewer

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Others

  • Hyperledger Cactus Whitepaper

    Hart Montgomery, Hugo Borne-Pons, Jonathan Hamilton, Mic Bowman, Peter Somogyvari, Shingo Fujimoto, Takuma Takeuchi, Tracy Kuhrt, Rafael Belchior

    As an early contributor of the project (starting March 2020), I gave my contribution to Hyperledger Cactus whitepaper.

    Responsible for the efforts on writing several academic papers on Cactus. Progress is tracked via a public repository, and presented at the Cactus Western Hemisphere meetings

    Internet Engineering Task Force (IETF) Contributor

    Rafael Belchior, Miguel Correia, Thomas Hardjono

    Reviewer of the ODAP draft.

    Main author of the DLT Gateway Crash Recovery Mechanism draft: this draft defines a crash fault tolerant gateway. Presented advances of this draft to the working group (e.g., slides attached).

    IEEE Student Member

    IEEE Student Member 97285283