Ethereum Foundation Ditches Poseidon Hash Function for SHA and BLAKE

The Ethereum Foundation has made an unexpected change to its post-quantum security strategy by dropping the Poseidon hash function in favor of more widely tested alternatives, specifically SHA and BLAKE. This shift affects plans for leanVM, a system designed to help process and verify large amounts of blockchain activity on Ethereum's mainnet.

According to researcher Justin Drake, the decision was made possible due to improvements in SNARKs (compact cryptographic proofs) that have made conventional hash functions efficient enough to handle the workload previously expected of Poseidon. A production-ready version of leanVM is targeted for 2027, with broader rollouts across Ethereum's consensus, data, and execution layers planned for 2028.

Sreeram Kannan, founder and CEO of Eigen Labs, noted that SHA and BLAKE offer a practical advantage over other post-quantum approaches because they have fewer known attack vectors. Collaborative work between Eigen Labs, the Ethereum Foundation, and zero-knowledge proof company Succinct has increased proving speeds by 2.5 times.