Gossipsub: A Gossip-Based Pubsub Protocol

About this talk

Yiannis Psaras explains GossipSub, the libp2p pubsub protocol used by Filecoin and other blockchain networks, and the security extensions developed to harden it against Sybil, eclipse, censorship, cold-boot, and covert flash attacks. He details the protocol mechanics including the global mesh, local mesh degree D with D_low and D_high thresholds, heartbeat-driven graft and prune operations, and the eager-push plus lazy-pull gossip exchange where only message IDs are forwarded outside the mesh. The core hardening is a per-peer score function combining time-in-mesh, first-message deliveries, mesh failure penalties, invalid messages, an application-specific term, and IP colocation, complemented by mitigation strategies such as controlled mesh maintenance, flood publishing of first-seen messages, and prune backoff. Using Testground simulations with 5,000 peers and a 20:1 attacker-to-honest ratio, Psaras shows that GossipSub keeps propagation under the six-second Filecoin deadline across all attack scenarios while the Bitcoin and Ethereum 1 pubsub equivalents degrade significantly, and demonstrates how honest peers progressively prune attacker connections to reconstitute an honest-only mesh.