Anthropic said Claude Mythos Preview discovered improved attacks against two cryptographic algorithms, showing that frontier AI models can identify mathematical weaknesses that escaped years of human review.
The first finding significantly weakens HAWK, a post quantum digital signature scheme being evaluated by the National Institute of Standards and Technology. The second improves an attack against a reduced version of the Advanced Encryption Standard by between 200 and 800 times.
Neither result affects systems currently in use. HAWK has not been deployed, while the AES attack applies only to a seven round research version rather than the complete ten round AES 128 cipher.
Claude identified a previously unused mathematical symmetry in HAWK that enabled a faster key recovery attack and effectively cut the scheme’s key strength in half.
For the smallest HAWK 256 configuration, the estimated cost of recovering a key fell from 2 to the power of 64 operations to 2 to the power of 38.
