Anthropic says Claude Mythos Preview helped derive an end-to-end key-recovery attack against HAWK-256 and a 200- to 800-fold speedup for an attack on seven-round AES-128.
The HAWK attack exploits a previously unused symmetry in the lattice behind the signature scheme. Anthropic's released implementation gives an expected end-to-end runtime of about three hours and 42 minutes on a 96-core server. The AES result removes a 256-way guessing step from an existing meet-in-the-middle attack.
Anthropic said neither result affects production systems. HAWK remains a candidate in a National Institute of Standards and Technology (NIST) post-quantum standardization process, and the public recovery code only targets the smaller HAWK-256 parameter.
The Advanced Encryption Standard (AES) result applies to seven of AES-128's ten rounds and still requires an impractical number of chosen plaintexts. The company said no production software needs to change as a result.
Anthropic published the findings alongside two technical papers and reproducibility artifacts. The company said Mythos Preview largely conducted the research itself, with humans supplying project direction, computing resources, and extensive verification.
