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Ethereum Foundation researcher Justin Drake said the Foundation is abandoning Poseidon as a candidate hash primitive for Ethereum layer 1 and is instead moving toward standard hashes such as SHA or BLAKE. The shift was not triggered by a practical break of deployed Poseidon parameters; rather, advances in binary-field SNARK systems including Binius and Flock have made proving standard hashes efficient enough that Ethereum no longer needs a SNARK-friendly hash optimized for older proving constraints.
The change affects future roadmap discussions rather than live mainnet systems, because the proposed hash-related consensus, data, and execution changes have not been deployed or formally adopted through Ethereum governance. Ethereum had previously invested heavily in Poseidon review, including a paused $992,000 collision bounty, and researchers reported partial collisions and reduced-round results without demonstrating a practical break of recommended full-round parameters. The move aligns with Ethereum's broader future-proofing work, including its published focus on quantum resistance, while reducing reliance on newer cryptographic primitives whose security confidence has lagged behind changing engineering assumptions.
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Justin Drake announced that the Ethereum Foundation is abandoning Poseidon as a candidate hash primitive for Ethereum layer 1 and pivoting toward standard hashes such as SHA or BLAKE. The stated reason was that advances such as Binius and Flock made proving standard hashes fast enough, reducing the need for a SNARK-friendly hash.
The Ethereum Foundation paused its Poseidon1 Collision Prize, which had a $992,000 budget and had been scheduled to run until January 2029.
The Ethereum Foundation verified further CICO challenge solutions as cryptanalysis of Poseidon continued.
Ethereum published its roadmap page on post-quantum cryptography and quantum resistance.
The Ethereum Foundation verified additional solutions to CICO challenges under its Poseidon cryptanalysis program.
The first tier of the Poseidon1 collision prize was claimed with a three-element partial collision against the full-round Poseidon1 compression function, earning a $32,000 award.
The Ethereum Foundation verified solutions to CICO challenges as part of its Poseidon cryptanalysis effort.
Vitalik Buterin said the Foundation's cryptanalysis program had found security issues in Poseidon2 serious enough to consider adding rounds or reverting to Poseidon1. He also said he resisted adding a Poseidon execution-layer precompile because replacing an enshrined version later would create long-term maintenance burden.
A November 2025 lean consensus plan specified LeanVM over the KoalaBear prime and included POSEIDON_16 and POSEIDON_24 permutation precompiles.
Justin Drake published the Lean Ethereum proposal, which envisioned hash-based aggregate signatures for consensus, hash-based commitments for the data layer, and hash-based real-time zkVMs replacing re-execution.
The Ethereum Foundation launched the Poseidon Cryptanalysis Initiative, run by George Kadianakis, Dmitry Khovratovich, and Antonio Sanso with an advisory board of external experts. The initiative set multiple funding tracks, including bounty programs, research grants, attack-paper awards, and a $992,000 collision prize.
Poseidon2 followed Poseidon with improved native performance, but later drew enough security concern to prompt discussion of extra rounds or reverting to Poseidon1.
The Poseidon hash function was presented at USENIX Security, marking a major public milestone in its adoption and review.
Poseidon, an arithmetization-oriented hash function for SNARK-friendly use, was published by Lorenzo Grassi, Dmitry Khovratovich, Christian Rechberger, Arnab Roy, and Markus Schofnegger.
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