The Ethereum Foundation is deprecating Poseidon, a zero-knowledge proof hash function, in favor of SHA and BLAKE family algorithms to strengthen resistance against quantum computing threats, according to a post by Ethereum Foundation researcher Justin Drake.
Posteidon was designed as a hash function optimized for zero-knowledge proofs on Ethereum, requiring fewer constraints than traditional algorithms and lowering computational overhead for privacy-preserving applications. SHA and BLAKE are both members of the SHA-3 family standardized by the National Institute of Standards and Technology.
SHA-256 anchors Bitcoin's proof-of-work consensus; BLAKE2 and BLAKE3 are faster variants used in privacy protocols including Signal and Zcash. Both carry substantially longer track records against cryptanalytic break attempts than Poseidon, which entered wider use only after Ethereum's transition to proof-of-stake in 2022.
Post-quantum cryptography readiness has become a regulatory and infrastructure priority across blockchains as quantum computing advances. U.S. standards bodies released post-quantum cryptography guidelines in 2022, and major exchanges and custody providers have begun auditing their hash implementations.
Posteidon deprecation affects zero-knowledge proving systems built on Ethereum, including rollup constructions and privacy contracts that rely on the function for proof generation and verification. Developers using Poseidon for proofs will need to migrate to SHA or BLAKE implementations or accept longer proof verification windows, as BLAKE and SHA require more circuit constraints in zero-knowledge contexts.
The Ethereum Foundation has not announced a hard deadline for Poseidon removal from the protocol layer. The shift does not require a consensus fork; applications currently using Poseidon can maintain support in parallel with SHA and BLAKE, allowing a gradual transition period.
Developers will need to audit and test migration paths for existing zero-knowledge infrastructure before Poseidon sees reduced support across client implementations.
