Byzantine reliable broadcast is a fundamental primitive in distributed systems that allows a set of processes to agree on a message broadcast by a dedicated process, even when some of them are malicious (Byzantine). It guarantees that no two correct processes deliver different messages, and if a message is delivered by a correct process, every correct process eventually delivers one. Byzantine reliable broadcast protocols are known to scale poorly, as they require Ω(n²) message exchanges, where n is the number of system members. The quadratic cost can be explained by the inherent need for every process to relay a message to every other process. In this paper, we explore ways to overcome this limitation by casting the problem to the probabilistic setting. We propose a solution in which every broadcast message is validated by a small set of witnesses, which allows us to maintain low latency and small communication complexity. In order to tolerate the slow adaptive adversary, we dynamically select the witnesses through a novel stream-local hash function: given a stream of inputs, it generates a stream of output hashed values that adapts to small deviations of the inputs. Our performance analysis shows that the proposed solution exhibits significant scalability gains over state-of-the-art protocols.
@InProceedings{bezerra_et_al:LIPIcs.OPODIS.2024.31, author = {Bezerra, Jo\~{a}o Paulo and Anikina, Veronika and Kuznetsov, Petr and Schiff, Liron and Schmid, Stefan}, title = {{Dynamic Probabilistic Reliable Broadcast}}, booktitle = {28th International Conference on Principles of Distributed Systems (OPODIS 2024)}, pages = {31:1--31:30}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-360-7}, ISSN = {1868-8969}, year = {2025}, volume = {324}, editor = {Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.31}, URN = {urn:nbn:de:0030-drops-225679}, doi = {10.4230/LIPIcs.OPODIS.2024.31}, annote = {Keywords: Reliable broadcast, probabilistic algorithms, witness sets, stream-local hashing, cryptocurrencies, accountability} }
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