Anthropic said its AI model Claude Mythos Preview found in 60 hours an attack that halves the effective key strength of HAWK, a quantum-resistant digital signature candidate, at a computing cost of about $100,000. Anthropic said Bitcoin, Ethereum, elliptic curve signatures, BIP-360, and NIST were not the direct targets of the attack. The Claude model sharply improved attack efficiency involving AES, the Poseidon hash function, Zcash, and a new shielded pool upgrade designed to remain recoverable even in a quantum-computing environment. HAWK had passed two rounds of review over two years by a group of experts. The research does not directly affect the current security of Bitcoin or Ether.