Anthropic Says Claude Mythos Preview Cut a HAWK Post-Quantum Attack From 2^64 to 2^38 in Roughly 60 Hours
Anthropic's Frontier Red Team published on 2026-07-28 that Claude Mythos Preview found a previously unknown attack on HAWK, a NIST post-quantum signature candidate, reducing the cost of recovering the smallest key from 2^64 to 2^38 operations. The work took about 60 hours with a multi-agent research system and a human collaborator who is not a lattice cryptography specialist. Claude also produced a new fingerprinting technique called 'Möbius Bridge' that makes an existing meet-in-the-middle attack on 7-round AES-128 between 200 and 800 times faster, consuming roughly one billion output tokens over three days of autonomous work at about $100,000 per primary attack. Neither result affects production systems: HAWK is undeployed and the AES result is reduced-round only.
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