Ethereum Abandons Poseidon After 8 Years

Short version: big rethink, no panic

Ethereum researcher Justin Drake announced that the Foundation is stepping away from using the Poseidon hash for future layer‑1 designs and is leaning back toward conventional hashes like SHA and BLAKE. This isn’t a crisis moment — Poseidon hasn’t been broken and there’s no migration order — but the math landscape changed enough that the original tradeoffs no longer look as lopsided as they once did.

Why this actually matters (and how we got here)

Quick background: many zero‑knowledge proof systems (SNARKs) prefer arithmetic done over big prime fields. Classic, bit-twiddly hash functions like SHA‑256 or Keccak used to be expensive to prove inside those systems, so researchers invented special SNARK‑friendly hashes — Poseidon among them — that map neatly to the proof math.

Recently, though, proof techniques have improved in ways that flip that calculation. New approaches make proving batches of standard hash operations much cheaper, and some constructions work better with binary (0/1) logic, which meshes nicely with the usual bitwise hashes. Benchmarks from proof-of-concept work show surprisingly strong numbers: for example, a single modern M4 Max core can reportedly prove tens of thousands of hash compression operations per second (roughly on the order of 80k for BLAKE3-style compressions, 40k for SHA‑256, and 30k for Keccak in one set of tests), and multi‑core setups scale those totals up substantially.

Worth noting: these numbers count internal hash operations in a lab benchmark. That’s not the same as measuring live transaction throughput or how a real chain would behave, but the results still shift the engineering calculus. In plain English: we now have hash‑friendly SNARK techniques, so the main reason to use a bespoke hash is weaker than it used to be.

What’s next for Ethereum and for users

Practically speaking, this is about architecture choices for a future proof‑centric L1. Ethereum’s security plans already call for simplifying the protocol to reduce attack surface. One piece of the roadmap envisions swapping out current validator signatures for hash‑based, post‑quantum‑resistant schemes (think leanXMSS), then using a leanVM layer to squash their bigger data blobs into compact proofs. If conventional hashes become cheap to prove, that makes this whole design easier to pull off.

Timelines are long and conservative: Drake’s personal estimate puts a production‑grade leanVM around 2027 with broader deployments in 2028, while the Foundation’s official post‑quantum goals hover around 2029 and beyond for full execution‑layer migration. Users don’t need to do anything — wallets stay as they are, and existing rollups and zkVMs are not being told to change right now. This decision is about what foundation stones Ethereum might choose down the road, not an immediate switchboard flip.

So, same network, fewer surprises today, but a little chessboard rearranging for the future. Old school hashes might be back in vogue — who knew cryptographic fashion had comeback seasons?