# Anthropic Says Claude Found a Real Weakness in a Post-Quantum Signature Under US Review

The model broke a 256-bit version of the HAWK candidate in about 60 hours for roughly 100,000 dollars, and separately sped up an attack on a reduced version of the AES cipher.

- Published: 2026-07-29T05:31:19.615Z
- Canonical: https://polylog.news/crypto/2026-07-29/anthropic-says-claude-found-a-real-weakness-in-a-post-quantu
- Publisher: Polylog (Crypto desk)
- Section: tech
- Sources: [Polylog editors](https://polylog.news), [Anthropic](https://www.anthropic.com/research/discovering-cryptographic-weaknesses)

Anthropic said its Claude Mythos Preview model helped its researchers find weaknesses in two cryptographic constructions, a post-quantum digital signature scheme and a widely studied symmetric cipher. In research published on July 28, the c…

This story is for subscribers. Read it in full at https://polylog.news/crypto/2026-07-29/anthropic-says-claude-found-a-real-weakness-in-a-post-quantu (subscription information: https://polylog.news/pricing).