Goodbye, Poseidon!
An epic 8-year, 8-figure rabbit hole in post-quantum cryptography reaches its dream conclusion. The Ethereum Foundation is abandoning Poseidon for L1, pivoting to SHA or BLAKE. This milestone unlocks ultimate security for lean Ethereum and foreshadows a golden era of hash-based cryptography.
Since 2018, the Ethereum Foundation has invested in magic cryptographic bricks, so-called “SNARK-friendly hashes”. In 2019, Poseidon was born. It held strong and became the dominant SNARK-friendly hash, securing billions via zkrollups and zkVMs.
In a stunning reversal, breakthrough SNARK designs show that SNARK-friendly hashes aren’t necessary after all. Off-the-shelf traditional hash functions like SHA2 and BLAKE2s can now match Poseidon in a SNARK. In hindsight the key was not SNARK-friendly hashes, but hash-friendly SNARKs.
The secret is doing maths over the smallest prime number: 2. So-called “binary fields” natively speak the language of bits, aligning with the boolean operations inside traditional hashes. This is a stark departure from “prime fields”, where awkward large-prime arithmetic makes bit manipulation painfully expensive.
We’re talking sci-fi cryptography. 1M traditional hash calls proven per second, on a laptop. Just 100x overhead vs native CPU boolean compute. Nobody predicted such performance, not even the handful of binary-field visionaries. Hat tip to the research geniuses:
Jim and Ben with Binius in 2023;
See Succinct Arguments over Towers of Binary Fields
spoiler
Abstract
We introduce an efficient SNARK for towers of binary fields. Adapting Brakedown (CRYPTO '23), we construct a multilinear polynomial commitment scheme suitable for polynomials over tiny fields, including that with just two elements. Our commitment scheme, unlike those of previous works, treats small-field polynomials with no embedding overhead. We further introduce binary-field adaptations of HyperPlonk (EUROCRYPT '23)'s product and permutation checks and of Lasso (EUROCRYPT '24)'s lookup. Our binary PLONKish variant captures standard hash functions—like Keccak-256 and Grøstl—extremely efficiently. With recourse to thorough performance benchmarks, we argue that our scheme can efficiently generate precisely those Keccak-256-proofs which critically underlie modern efforts to scale Ethereum.
Ron, Benedikt and William with Flock in June.
See Flock: Fast Proving for Batch Boolean Computations
spoiler
Abstract
For many applications of SNARKs, a key bottleneck is proving large batches of standard cryptographic hash evaluations, such as SHA-256, Keccak, or BLAKE3. We introduce Flock, a hash-based SNARK for extremely fast proving of such batched Boolean computations. Flock proves batches of the same R1CS circuit (plus input/output relations between them), can prove hash-chains and Merkle path openings, and in principle can be extended to full-fledged hash-based signature verification. At its core, Flock combines new optimizations for the lincheck and zerocheck protocols with an aggressively optimized proof-of-concept implementation co-designed by coding agents.
On a single core of an M4 Max processor, Flock proves 82k evaluations of the BLAKE3 compression function, 42k SHA-256 compressions, and 30k Keccak permutations per second — less than a overhead over native execution. On ten cores, throughput exceeds 660k BLAKE3 compressions per second; in proving SHA-256, Flock is more than faster than Binius64, the prior state of the art, and more than faster than the fastest elliptic curve-based SNARK we measured against.
With SHA2, the lean aesthetic of minimal assumptions reaches its climax. The EF’s principled stance on pure hash-based cryptography has aged like fine wine. We now enjoy foundations the world can trust for decades and centuries, foundations worthy of the dream of an internet of value.
Speed of deployment is a secondary win. There’s no longer a need to wait years for Poseidon cryptanalysis to bake. Emile and Thomas from the EF post-quantum team are moving at breakneck speed with binary fields. The strawmap now points to a production-grade leanVM in 2027, with CL, DL, EL deployments in 2028.
As AI becomes exceptional at cryptanalysis, the contrarian bet to avoid riskier structures like lattices and isogenies is visibly paying off. The past weeks have been brutal. Lattice-based “HAWK” and isogeny-based “SQIsign”, both signature schemes in NIST’s Round 3, have suffered blows. Sources I trust say more blood is coming.
On AI, the open autoresearch trend kicked off by ECDSA.fail is spreading fast, with amazing outcomes from zk.golf and SNARK.fast. Days ago SNARK.fast crossed 1.8M BLAKE3/sec proven on an M3 Max. Stay tuned for fresh autoresearch challenges dropping tomorrow.
Also tomorrow: Ethproofs call #10, dedicated to binary fields. Possibly the most noteworthy Ethproofs call yet. Experts leading the charge will present the future of hash-based SNARKs at 2pm UTC. What an incredible time to be alive. To witness history, DM me for a calendar invite :)
Today I can confidently claim that hash-based cryptography has won out for blockchain post-quantum signatures. SNARK succinctness compresses arbitrarily many signatures into one small proof per block. SNARK flexibility yields k-of-n threshold signatures, complex multisigs, and more.
Ultimate security. Uncompromising performance. Full programmability.
Believe in something. Believe in hashes.
Credits to Justin Drake