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DBFT: Efficient Leaderless Byzantine Consensus

This paper introduces a new leaderless Byzantine Consensus called the Democratic Byzantine Fault Tolerance (DBFT) blockchain consensus.

Authored by:
Tyler Crain, University of Sydney
Vincent Gramoli, University of Sydney
Mikel Larrea, Univ. of the Basque Country UPV/EHU
Michel Raynal, Universite de Rennes


While most blockchain consensus protocols rely on a correct leader or coordinator to terminate, our algorithm can terminate even when its coordinator is faulty.

The key idea is to allow processes to complete asynchronous rounds as soon as they receive a threshold of messages, instead of having to wait for a message from a coordinator that may be slow.

The resulting decentralization is particularly appealing for blockchains for two reasons:

(i) each node plays a similar role in the execution of the consensus, hence making the decision inherently “democratic”;

(ii) decentralization avoids bottlenecks by balancing the load, making the solution scalable. DBFT is deterministic, assumes partial synchrony, is resilience optimal, time optimal and does not need signatures.

We first present a simple safe binary Byzantine consensus algorithm, modify it to ensure termination, and finally present an optimized reduction from multivalue consensus to binary consensus whose fast path terminates in 4 message delays.

This paper was co-authored by our CTO and Founder Professor Vincent Gramoli.

Professor Vincent Gramoli is a full professor at the University of Sydney. He is a researcher in the field of distributed systems and algorithms, with a focus on the design and analysis of distributed systems and algorithms for shared memory and data-centric systems, including distributed hash tables, distributed shared memory and transactional memory. He has published numerous papers in top-tier conferences and journals in the field and has received several awards for his research. He is also currently serving as the Head of Concurrent Systems Research Group at the University of Sydney.

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