Claude found mathematical flaws in two cryptographic algorithms that years of expert review missed

Anthropic announced on Monday that Claude Mythos Preview has discovered mathematical weaknesses in two cryptographic algorithms. The first substantially weakens HAWK, a post-quantum digital signature scheme under review by NIST, by cutting its effective key strength in half. The second improves the best-known attack on seven-round AES, the most widely used symmetric cipher, by 200-800x.