Ethereum Foundation abandons Poseidon hash in favor of SHA or BLAKE for planned post-quantum systems, with leanVM targeted for production by 2027.
The Ethereum Foundation is changing course on a key piece of its post-quantum security strategy, dropping the Poseidon hash function in favor of more widely tested alternatives. Researcher Justin Drake made the announcement Aug. 13, naming SHA and BLAKE as potential replacements.
The shift affects plans for leanVM, a system designed to help Ethereum (ETH) process and verify large amounts of blockchain activity more efficiently. LeanVM and similar post-quantum tools have not yet been deployed on Ethereum's mainnet.
Drake credited improvements in SNARKs for making the change possible. SNARKs are compact cryptographic proofs that confirm a computation took place without repeating all the underlying work. As SNARK technology has matured, conventional hash functions have become efficient enough to handle the workload that Poseidon was once expected to take on.
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Drake outlined a rough timeline for what comes next. A production-ready version of leanVM is targeted for 2027, with broader rollouts across Ethereum's consensus, data, and execution layers planned for 2028. He described both dates as preliminary.
Sreeram Kannan, founder and CEO of Eigen Labs, said SHA and BLAKE offer a practical advantage over other post-quantum approaches because they have fewer known attack vectors. Both functions have been subject to public scrutiny for years, which Kannan said should allow faster deployment compared with less-tested alternatives.
Kannan also said that collaborative work between Eigen Labs, the Ethereum Foundation, and zero-knowledge proof company Succinct had increased proving speeds by 2.5 times. That gain is part of what makes conventional hashes a viable replacement for Poseidon in the planned systems.
A hash function converts input data into a fixed digital fingerprint. Computers use that fingerprint to check whether information has been altered. Selecting hash functions that can resist attacks from future quantum computers is considered a foundational step in Ethereum's long-term security planning.
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