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Probabilistic Chained Blockchain Consensus
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| 4.56 MB | Adobe PDF |
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Resumo(s)
Byzantine Fault Tolerant (BFT) consensus protocols are a fundamental building block for blockchain and distributed systems, traditionally designed under pessimistic assumptions that guarantee safety and liveness even under arbitrary adversarial behavior. While robust, this approach often limits performance and scalability, particularly in large replica systems. Existing protocols face a trade-off: achieving low latency with quadratic message complexity (e.g. PBFT, Simplex) or, reducing message complexity at the expense of additional communication steps and increased latency (e.g. HotStuff, Jolteon). Building on this foundation, ProBFT, a recent probabilistic BFT consensus protocol for partially synchronous systems, achieves sub-quadratic message complexity and optimal good-case latency of three communication steps by relaxing pessimistic assumptions while providing strong theoretical guarantees. However, ProBFT has never been implemented and only solves the single-shot consensus problem. To overcome this drawback, we develop Practical Simplex, an adaptation of Simplex that solves its main practical limitation: the unbounded growth of communication complexity required to guarantee liveness. Then, ProBFT’s core mechanisms are integrated into Practical Simplex. This integration results in ProSimplex, a probabilistic chained consensus protocol that preserves Simplex’s simple approach to consensus while leveraging probabilistic quorums to achieve sub-quadratic message and communication complexity, improving scalability. ProSimplex and Practical Simplex are implemented and experimentally evaluated, and compared with Jolteon, a state-of-the-art chained consensus protocol. Experimental results show that ProSimplex scales better than Practical Simplex and Jolteon in terms of throughput for larger systems while exhibiting higher finalization latency when compared with Practical Simplex due to its probabilistic nature. For smaller systems, the cryptographic overhead of ProSimplex reduces throughput relative to the other protocols. Jolteon exhibits the highest finalization latency due to having more communication steps. Additionally, the results show that the throughput of all three protocols is closer than expected, due to the shared overhead of broadcasting large block proposals.
Descrição
Tese de mestrado, Engenharia Informática, 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Byzantine Fault Tolerance Blockchain Probabilistic Consensus Scalability Distributed Systems