The Ethereum Foundation is no longer planning to use the Poseidon hash function in the post-quantum systems it is designing for Ethereum. Researcher Justin Drake said the foundation is instead shifting toward established hash functions such as SHA or BLAKE.

Poseidon had been under consideration for future components including leanVM, a proposed system intended to help Ethereum verify large amounts of blockchain activity efficiently. Those designs remain in development and have not been deployed on Ethereum mainnet.

Why the design changed

According to Drake, recent advances in SNARKs, or compact cryptographic proofs, have reduced the need for a specialized hash such as Poseidon in the foundation’s planned architecture. In his account, conventional hashes can now perform well enough in those systems to replace the earlier choice.

That marks a notable change in direction because Poseidon had been seen as part of Ethereum’s future post-quantum stack. The revised approach favors more widely used cryptographic tools rather than a hash designed specifically for zero-knowledge-heavy environments.

LeanVM remains a future deployment

One of the systems tied to the discussion is leanVM, which is being developed to improve Ethereum’s ability to verify large volumes of blockchain activity efficiently. The project is still ahead of deployment rather than already active on the network.

The current target is to make leanVM production-ready in 2027. Broader rollouts across Ethereum’s consensus, data and execution layers are planned for 2028, indicating that the post-quantum effort is still on a multiyear timeline.

Security and implementation considerations

Eigen Labs founder and CEO Sreeram Kannan said established hash-based systems may offer practical advantages. He argued they have fewer known attack avenues and could be deployed more quickly because they have already undergone substantial scrutiny.

Kannan also said joint work involving Eigen Labs, the Ethereum Foundation and zero-knowledge proof company Succinct improved proving speeds by about 2.5x. That reported gain helps explain why the performance case for keeping Poseidon appears to have weakened.

What comes next

The immediate implication is a refinement of Ethereum’s planned post-quantum design rather than a live network change, since the systems under discussion are not yet on mainnet. For now, the clearest confirmed milestones remain the foundation’s stated targets: a production-ready leanVM in 2027 and wider deployment efforts in 2028.

Whether SHA, BLAKE or another established option becomes the final choice, the foundation’s latest position suggests it now prefers mature cryptographic primitives as it prepares the next stage of Ethereum infrastructure.

Source: cointelegraph.com