Ethereum Foundation abandons Poseidon hash function in post-quantum roadmap

The Ethereum Foundation is abandoning the Poseidon hash function on its base layer, pivoting to established alternatives like SHA or BLAKE. Announced by researcher Justin Drake on August 13, 2026, the shift concludes an eight-year research effort. Advances in SNARKs and binary-field proofs, which boosted proving speeds by 2.5 times in joint work with Succinct, make conventional hashes practical. Ethereum targets a production-ready leanVM for 2027, with layer deployments planned for 2028.

Poseidon hash function abandonment

• ▪Ethereum Foundation researcher Justin Drake announced the decision to abandon the Poseidon hash function on August 13, 2026, marking the conclusion of an eight-year research effort.
• ▪The Poseidon hash function was previously considered for future post-quantum systems like leanVM to help Ethereum verify large volumes of blockchain activity, though these systems have not yet been deployed on the mainnet.
• ▪The Ethereum Foundation is abandoning the Poseidon hash function on its base layer and moving to established alternatives like SHA or BLAKE.

SNARK proof system advances

• ▪Joint development work by the Ethereum Foundation, Eigen Labs, and zero-knowledge proof company Succinct has increased proving speeds by 2.5 times.
• ▪Advances in SNARKs, which are compact proofs used to confirm computations, allow conventional hashes like SHA and BLAKE to perform efficiently enough to replace the Poseidon hash function.

Post-quantum roadmap timeline

• ▪The Ethereum Foundation preliminarily plans to deploy post-quantum architecture across Ethereum's consensus, data, and execution layers in 2028.
• ▪The Ethereum Foundation targets a production-ready leanVM, which helps verify blockchain activity, for release in 2027.

Established hash function security advantages

• ▪The transition to SHA and BLAKE is driven by faster binary-field proofs making them practical, rather than declaring the Poseidon hash function broken.
• ▪Eigen Labs founder and CEO Sreeram Kannan stated that established hash-based systems have fewer known avenues of attack than other post-quantum approaches and can be deployed faster due to years of scrutiny.

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