publications

2025

1. Usenix Sec

   Recover from Excessive Faults in Partially-Synchronous BFT SMR

   Tiantian Gong, Gustavo F. Camilo, Kartik Nayak, and 2 more authors

   Accepted to USENIX Security Simposyum, 2025

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   Byzantine fault-tolerant (BFT) state machine replication (SMR) protocols form the basis of modern blockchains as they maintain a consistent state across all blockchain nodes while tolerating a bounded number of Byzantine faults. We analyze BFT SMR in the excessive fault setting where the actual number of Byzantine faults surpasses a protocol's tolerance.

   We start by devising the very first repair algorithm for linearly chained and quorum-based partially synchronous SMR to recover from faulty states caused by excessive faults. Such a procedure can be realized using any commission fault detection module -- an algorithm that identifies the faulty replicas without falsely locating any correct replica. We achieve this with a slightly weaker liveness guarantee, as the original security notion is impossible to satisfy given excessive faults.

   We implement recoverable HotStuff in Rust. The throughput resumes to the normal level (without excessive faults) after recovery routines terminate for replicas and is slightly reduced by for replicas. On average, it increases the latency by for replicas.

   Aside from adopting existing detection modules, we also establish the sufficient condition for a general BFT SMR protocol to allow for complete and sound fault detection when up to Byzantine replicas (out of total replicas) attack safety. We start by providing the first closed-box fault detection algorithm for any SMR protocol without any extra rounds of communication. We then describe open-box instantiations of our fault detection routines in Tendermint and Hotstuff, further reducing the overhead, both asymptotically and concretely.

2024

1. IEEE COMST

   A Survey on Blockchain Scalability: From Hardware to Layer-two Protocols

   Gabriel Antonio F. Rebello, Gustavo F. Camilo, Lucas Airam C. Souza, and 4 more authors

   In IEEE Communications Surveys and Tutorials, 2024

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2. IEEE TNSM

   ProfitPilot: Enabling Rebalancing in Payment Channel Networks through Profitable Cycle Creation

   Gustavo F. Camilo, Gabriel Antonio F. Rebello, Lucas Airam C. Souza, and 2 more authors

   In IEEE Transactions on Network and Service Management, 2024

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2022

1. ICC

   A Blockchain-based System for Secure and Distributed Virtual Network Functions Orchestration

   Gustavo F. Camilo, Lucas Airam C. Souza, Miguel Elias M. Campista, and 2 more authors

   In ICC 2022 - IEEE International Conference on Communications, 2022

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   Service provisioning in next-generation networks, such as 5G and 6G, relies on virtualization to carry out multi-domain and multi-tenant connections. In these scenarios, virtual network functions (VNF) orchestration becomes susceptible to security threats once trust between peers cannot be assumed. This paper 1 proposes a blockchain-based system for an agile, secure, and distributed provisioning of virtual network functions in scenarios with multiple administrative domains. Our proposal employs smart contracts to deliver all stages of a service-level-agreement management life cycle automatically. We develop, implement, and evaluate a prototype of the proposed system using smart contracts running on Hyperledger Fabric. The performance evaluation results show that the system guarantees high-rate VNF provisioning, reaching hundreds of slice requests per second in a trustful way.

2. INFOCOM

   PCNsim: A Flexible and Modular Simulator for Payment Channel Networks

   Gabriel Antonio F. Rebello, Gustavo F. Camilo, Maria Potop-Butucaru, and 3 more authors

   In IEEE INFOCOM 2022 - IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), 2022

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   Payment channel networks (PCN) enable the use of cryptocurrencies in everyday life by solving the performance issues of blockchains. Nevertheless, the main implementations of payment channel networks lack the flexibility to test new proposals that can address fundamental challenges, such as efficient payment routing and maximization of the payment success rate. In this demo paper, we propose PCNsim, an open-source simulator based on OMNeT++, which fully reproduces the default behavior of a payment channel network. We build the simulator in a modular architecture that allows easy topology/workload customization and automates result visualization. The core mechanism of PCNsim implements the specifications of the Lightning Network. We evaluate our proposal with a dataset of credit card transactions in a scale-free topology and show that it successfully demonstrates the difference between two routing methods in different setups.

2021

1. Ann. Telecommun.

   A security and performance analysis of proof-based consensus protocols

   Gabriel Antonio F Rebello, Gustavo F Camilo, Lucas CB Guimaraes, and 3 more authors

   Annals of Telecommunications, 2021

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   Blockchain is a disruptive technology that will revolutionize the Internet and our way of living, working, and trading. However, the consensus protocols of most blockchain-based public systems show vulnerabilities and performance limitations that hinder the mass adoption of blockchain. This paper presents and compares the main proof-based consensus protocols, focusing on the security and performance of each consensus protocol. Proof-based protocols use the probabilistic consensus model and are more suitable for public environments with many participants, such as the Internet of Things (IoT). We highlight the centralization tendency and the main vulnerabilities of Proof of Work (PoW), Proof of Stake (PoS), and their countermeasures. We also analyze and compare alternative proof-based protocols, such as Proof of Elapsed Time (PoET), Proof of Burn (PoB), Proof of Authority (PoA), and Delegated Proof of Stake (DPoS). Finally, we analyze the security of the IOTA consensus protocol, a DAG-based platform suited for the IoT environment.

2. GLOBECOM

   Architecture and Performance Comparison of Permissioned Blockchains Platforms for Smart Contracts

   Guilherme A. Thomaz, Gustavo F. Camilo, Lucas Airam C. Souza, and 1 more author

   In 2021 IEEE Global Communications Conference (GLOBECOM), 2021

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   Blockchain and Smart Contracts ensure security and automation in trustless scenarios, leading to innovative solutions in various industry branches. The Hyperledger open-source project adopts these technologies in the corporate business, providing platforms for developing distributed applications. This paper analyses and compares two widely used platforms to develop applications based on permissioned blockchains: Hyper-ledger Sawtooth and Hyperledger Fabric. We implement two prototypes based on the same smart contract to evaluate the performance of each tool. The results show that: i) Sawtooth parallel transaction execution performs up to 30% better than serial execution only if the number of conflicting transactions remains low, and ii) Fabric has a much faster consensus protocol, but presents a low performance if the transactions are conflicting.

3. Blockchain

   DAGSec: A hybrid distributed ledger architecture for the secure management of the Internet of Things

   Igor D. Alvarenga, Gustavo F. Camilo, Lucas A. C. De Souza, and 1 more author

   In 2021 IEEE International Conference on Blockchain (Blockchain), 2021

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   The rise of 5G mobile broadband networks creates new possibilities for the Internet of Things. Billions of devices will provide comprehensive services, including e-health applications, smart grids, and industry 4.0. Distributed ledger technologies solve most security and privacy threats of current IoT systems connected to a cloud or multi-access edge communication (MEC). Unfortunately, the volume of transactions imposed by 5G networks prevents blockchain-based solutions due to scalability issues. Nonetheless, emerging solutions based on directed acyclic graphs (DAG), still require some form of centralization or global view. This article proposes DAGSec, a hybrid distributed ledger architecture that provides a secure Internet of Things environment with high throughput and low latency. Our proposal uses directed acyclic graphs and local transaction validation instead of global transaction validation to attain a high transaction rate. Furthermore, we propose a blockchain-based witness system to approximate chronological order of independent transactions.

2020

1. GLOBECOM

   AutAvailChain: Automatic and Secure Data Availability through Blockchain

   Gustavo F. Camilo, Gabriel Antonio F. Rebello, Lucas Airam C. Souza, and 1 more author

   In GLOBECOM 2020 - 2020 IEEE Global Communications Conference, 2020

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   The trust centralization in current data sharing systems restricts the owner’s control over their data. Furthermore, the owner’s intervention to authorize his/hers data access for each request makes frequent access to popular data tiresome. In this paper, we propose AutAvailChain, an architecture based on software defined networking (SDN) and blockchain to provide secure, automatic, and distributed sharing of IoT data. We develop a prototype using the Hyperledger Fabric platform to implement the blockchain and a smart contract. The results show a quick, secure, and excellent performance of dozens of transactions per second.

2. Blockchain

   A Secure Personal-Data Trading System Based on Blockchain, Trust, and Reputation

   Gustavo F. Camilo, Gabriel Antonio F. Rebello, Lucas Airam C. Souza, and 1 more author

   In 2020 IEEE International Conference on Blockchain (Blockchain), 2020

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   Every citizen has the right to privacy and, therefore, the right to control their personal information, deciding to whom, when, and where their information is available. This paper proposes a secure, agile, and effective system for a distributed, automatic, and transparent data trading between domains using blockchain, smart contracts, trust, and reputation. We develop and implement a prototype of a trust and reputation system based on real-life interactions. The results show that the proposed system provides security and privacy in a quick and distributed way, performing hundreds of transactions per second, and effectively punishing malicious behavior.

3. Blockchain

   DFedForest: Decentralized Federated Forest

   Lucas Airam C. Souza, Gabriel Antonio F. Rebello, Gustavo F. Camilo, and 2 more authors

   In 2020 IEEE International Conference on Blockchain (Blockchain), 2020

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   The effectiveness of machine learning systems depends heavily on the relevance of the training data. Usually, the collected data is sensitive and private because it comes from devices and sensors used in people’s daily lives. The General Data Protection Regulation (GDPR) in Europe, the California Consumer Privacy Act (CCPA) in California, and China’s Cybersecurity Law put the current approach at risk, as it prohibits centralized remote processing of sensitive data collected in a distributed manner. This paper proposes a distributed machine learning system based on local random forest algorithms created with shared decision trees through the blockchain. The results show that the proposed approach equals or exceeds the results obtained with the use of random forests with only local data. Furthermore, the proposal increases the detection of new attacks when the domains have different threat distributions.

2019

1. HPSR

   Providing a Sliced, Secure, and Isolated Software Infrastructure of Virtual Functions Through Blockchain Technology

   Gabriel Antonio F. Rebello, Gustavo F. Camilo, Leonardo G. C. Silva, and 4 more authors

   In 2019 IEEE 20th International Conference on High Performance Switching and Routing (HPSR), 2019

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   Network slicing, network function virtualization (NFV), and software defined network (SDN) technologies provide agile on-demand end-to-end services. The identification of a faulty virtual function becomes mandatory because services allocate resources across a distributed and trustless environment composed by multi-tenant competing service providers. In this paper, we propose and develop a blockchain-based architecture to provide auditability to orchestration operations of network slices and to provide secure VNF configuration updates while ensuring isolation and privacy between network slices. A proof of concept prototype using the Hyperledger Fabric platform was developed in which network slice runs on an isolated channel. The results show that we can secure a network slice creation, but that the consensus and the number of transaction required by the slices are a great challenge.