> ## Content Index > Fetch the complete content index at: https://www.notatechguy.com/llms.txt > Use this file to discover other available public pages before exploring further. # Blockchain gossip protocols may miss quorum under attack - URL: https://www.notatechguy.com/blockchain-gossip-protocols-may-miss-quorum-under-attack/ - Published: 2026-10-18T08:12:33.000Z - Updated: 2026-10-18T08:12:33.000Z - Description: An arXiv preprint finds Bitcoin, Ethereum, Polkadot and Solana gossip parameters may be too thin to guarantee quorum under realistic attacks. - Author: Marcello Babbili - Tags: Technology & AI Ethereum, Solana, Polkadot and Bitcoin run gossip protocols that may fail to deliver consensus messages to enough honest nodes under attack, with Bitcoin needing a fanout above 15 for 5000-node networks, an arXiv preprint finds [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). The paper, posted on arXiv on 15 October 2026, puts four production gossip designs under the same adversarial lens [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). Its central claim: the graph parameters teams commonly choose to wire their validator networks are insufficient to guarantee quorum, the supermajority threshold that makes a block final [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). **My read:** This is the first cross-chain comparison I have seen that tests four production gossip designs against the same adversary model. I am cautious about one thing: the authors' descriptions of each network's topology may not match what is actually running in production today. The 15-degree fanout threshold is a simulation result, not a mainnet audit. Until an independent team reproduces these attacks against live validator sets, the findings are a well-structured warning, not a confirmed breach. ### Why complete graphs do not scale Committee-based blockchains run Byzantine fault-tolerant consensus, where a supermajority of validators must agree before a block is final. Ethereum and Polkadot committees run into the hundreds of nodes [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). At that scale, connecting every node to every other node, a complete graph, becomes impractical [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). So networks turn to gossip: each node forwards messages to a handful of neighbours, who forward to theirs, until the message reaches everyone. The handful is a design choice, and the paper shows the choice is often wrong. ### Four protocols, four tradeoffs The authors tested four designs: the Erdős-Rényi random graphs used by Bitcoin, Polkadot's grid, Ethereum's GossipSub, and Solana's tree-based and chunk-based dissemination [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). Each has a different weakness. Solana's dynamic trees save bandwidth when conditions are benign but break under adaptive attacks [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). Polkadot takes the opposite approach: its grid topology is resilient against adaptive attacks, but pays for that resilience with high bandwidth overhead [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). Ethereum's GossipSub, designed by Dimitris Vyzovitis and colleagues for Filecoin and Ethereum 2.0 [P²](https://arxiv.org/abs/2007.02754?ref=notatechguy.com), balances bandwidth efficiency with resistance to adaptive adversaries, but the paper finds it is highly sensitive to parameter choices [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). Get the settings wrong and the resilience evaporates. Bitcoin's Erdős-Rényi graphs, where each node connects to a random subset of peers, offer a strong tradeoff, but only when the average fanout degree, the number of neighbours each node maintains, stays above 15 in networks as large as 5000 nodes [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). Below that threshold, the random connections thin out enough that an adversary can isolate honest nodes before they receive consensus messages. ### What would have to hold The paper has not been peer-reviewed, and its findings come from analytical work and empirical measurements, not from confirmed attacks on live mainnets [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). No chain development team has endorsed or responded to the findings, and the 15-degree threshold has not been validated outside the authors' own tests. The authors' descriptions of each protocol's topology may also not match current production deployments. Networks upgrade their gossip layers, and a design described in a paper may already have been patched or replaced. ### Who should pay attention A validator operator running nodes on any of the four networks should check their gossip configuration against the paper's findings, particularly the fanout degree and connection parameters. A protocol team designing a new committee-based chain could use the tradeoff map, bandwidth cost versus adversarial resilience, to pick a starting architecture rather than defaulting to an ad hoc gossip setup [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). The paper does not recommend a single best protocol [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). The closest it comes is the Erdős-Rényi result: keep the fanout above 15 in networks up to 5000 nodes, and the random-graph approach holds its own against the more structured designs. The preprint, available on arXiv since 15 October 2026, awaits independent replication before its findings can be treated as confirmed [S¹](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com). --- *Sources: [S1 — On the Robustness of Gossip Protocols in Modern Blockchains](https://arxiv.org/abs/2610.21526v1?ref=notatechguy.com) · [P2 — \[2007.02754\] GossipSub: Attack-Resilient Message Propagation in the Fi](https://arxiv.org/abs/2007.02754?ref=notatechguy.com) · [P3 — libopenstorage/gossip](https://github.com/libopenstorage/gossip?ref=notatechguy.com) · [P4 — modernblockchains (@modernblockchains)](https://github.com/modernblockchains?ref=notatechguy.com) · [P5 — modernblockchains/newkidsontheblock](https://github.com/modernblockchains/newkidsontheblock?ref=notatechguy.com)* --- *Written from 5 sourced items, 4 of them primary.* ## More from Not A Tech Guy - [NVIDIA joins EU science initiative with 250 open models](https://www.notatechguy.com/nvidia-joins-eu-science-initiative-with-250-open-models/) - [Meta's 816B Muse Spark Open targets Mac Studios](https://www.notatechguy.com/meta-s-816b-muse-spark-open-targets-mac-studios/) - [Stack Overflow for Agents triples signups with ChatGPT plugin](https://www.notatechguy.com/stack-overflow-for-agents-triples-signups-with-chatgpt-plugin/)