# Cryptographers Dispute the Security of Poseidon, the Hash Function Underpinning Ethereum's Zero-Knowledge Proofs

One researcher put Poseidon's quantum preimage resistance at just 63.75 bits, well below common security targets, while a rival proposal called Ashlar is inviting cryptanalysts to try to break it before it is trusted with real value.

- Published: 2026-08-07T14:25:07.977Z
- Canonical: https://polylog.news/crypto/2026-08-07/cryptographers-dispute-the-security-of-poseidon-the-hash-fun
- Publisher: Polylog (Crypto desk)
- Section: crypto
- Sources: [Ethereum Research](https://ethresear.ch/t/poseidon-hash-for-ethereum-is-not-secure/25637), [Ethereum Research](https://ethresear.ch/t/ashlar-an-ao-hash-from-a-squaring-degree-engine-and-a-request-for-cryptanalysis/25634)

A thread posted to ethresear.ch this week argues that Poseidon, a hash function widely used inside zero-knowledge proof systems on Ethereum and its rollups, is not as secure as its deployment suggests. The post calculates Poseidon's classic…

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