The Ethereum Foundation is walking back one of its more ambitious cryptographic bets. After spending over a year evaluating the Poseidon hash function as a potential upgrade for base-layer hashing, the foundation is now favoring SHA and BLAKE3, two well-established alternatives with decades of security research behind them.
The reason is almost counterintuitive: the very zero-knowledge proof systems that made Poseidon attractive in the first place have gotten so much better that the exotic hash no longer offers a meaningful edge.
From darling to doubt
Poseidon first entered the conversation as a serious candidate in February 2025, when Vitalik Buterin floated the idea of migrating Ethereum’s base-layer hashing to Poseidon, pointing to its dramatically lower constraint counts inside ZK circuits. In plain terms, Poseidon was designed from the ground up to play nicely with zero-knowledge proofs, making it cheaper and faster to verify computations on-chain.
The hash function itself dates back to 2021, co-designed by cryptographer Dmitry Khovratovich. Its core selling point was reducing the computational overhead compared to Pedersen hashes, the incumbent in many ZK systems.
