AI Broke a NIST Candidate. Not Your Encryption

Table of Contents

• The three tiers of cryptographic failure
• What the two attacks actually do
• Both results extend published human work
• The standardization process worked exactly as designed
• Where this gets dangerous is the long tail
• Crypto-agility was always the point
• On what I wrote last year, and what needs updating
• What to do about this quarter
• The verification problem is the one to watch

July 28, 2026 – On July 28, Anthropic disclosed that Claude Mythos Preview had recovered signing-equivalent keys from two HAWK-256 challenge public keys, in a few hours, on one server. A separate team independently attacked the same scheme through a different mathematical path using GPT-5.6. In the same release, Mythos also improved the best-known attack on 7-round AES-128, a research target that had stood since 2013. The coverage has been predictably bad in both directions, so before going any further:

• No deployed system is affected. HAWK is a NIST candidate, not a standard. The AES result targets 7 of 10 rounds and requires $2^{105}$ chosen plaintexts. No key was recovered from any production system, and your algorithm roadmap does not change today.
• These are weaknesses in the algorithm designs themselves. The HAWK attack exploits a symmetry in the mathematical ring the designers chose. The AES attack exploits algebraic properties of the S-box as defined in the FIPS 197 standard. Any correct implementation inherits both properties. A software patch cannot fix a flaw in the specification. For HAWK, the response is reparameterization or a redesign; for AES, no response is needed because the full 10-round cipher absorbed the finding.
• ML-KEM, ML-DSA, SLH-DSA, Falcon, and production AES are untouched. The HAWK finding is specific to HAWK. It does not affect other lattice schemes or any finalized NIST standard.
• What changed is the economics of finding these flaws. A publishable cryptanalytic result now costs about USD 100,000 and a week of model time. Three independent efforts…