New post on Eth Research! SEACAST: fast, lean broadcast for Ethereum, with an executable spec and a formal model By: - cskiraly 🔗 ethresear.ch/t/26167 Highlights: - Ethereum’s broadcast problem is getting harder as objects grow (bigger execution payloads, DA data, possible future proofs and post-quantum signatures), and today’s gossip can be seconds late for home builders and wastes bandwidth with duplicates. - SEACAST combines segmented forwarding (send/forward chunks immediately), erasure coding (Reed–Solomon so no specific chunk is ‘the last one’), and availability sampling (nodes can request only required columns/rows/cells rather than full objects). - The protocol explicitly separates what a node wants (interest: full object vs custody columns vs samples) from what it must relay (duty) and from who it pushes vs merely announces to, avoiding ‘one topic per piece’ designs like many-column topics. - In simulations on identical network setups, SEACAST delivers faster and with fewer bytes than both today’s gossipsub and ECBroadcast’s RS mode; e.g., in an all-home 500-node network with 16 peers each, 99% reach for a 1 MiB payload is ~0.64s vs 0.97s (ECBroadcast) vs 4.5s (gossipsub), with much lower received bytes per node. - SEACAST is designed to be ‘elastic’ under thinner uplinks (delay tracks bandwidth without runaway duplication) and is unusually well-specified: it has an executable pseudocode spec plus a formal model (Quint/TLA+) that already found and helped fix multiple liveness gaps. ELI5: Ethereum nodes need to quickly share big “packages” of data with lots of other nodes. Today’s sharing is wasteful: nodes often wait until they have the whole package before forwarding it, and many nodes get multiple duplicate copies. SEACAST is a smarter way to share: it breaks data into small pieces, adds error-correcting coding so any enough pieces work, forwards pieces immediately, and lets nodes request only the pieces they actually need (sometimes just a sample). It also comes with a spec you can actually run like a program, plus a formal math model to find bugs in the rules.