Anthropic uses Claude Mythos Preview to discover cryptographic weaknesses in HAWK and AES

Anthropic researchers used Claude Mythos Preview to improve the attack on the post-quantum signature scheme HAWK, halving the effective key strength and reducing the key recovery cost for the small-size HAWK-256 from 2^64 to 2^38. Another result targets a 7-round reduced version of AES-128; Claude proposed a method called Möbius Bridge, making the attack 200 to 800 times faster than the previous best meet-in-the-middle attack. Neither result affects existing production systems; HAWK remains only a NIST third-round candidate, and the AES attack does not apply to the full 10-round encryption. Anthropic said each result cost about $100,000 in API costs, and it built the CryptanalysisBench benchmark in collaboration with ETH Zurich, Tel Aviv University, and Technische Universität Berlin.