Key takeaways
What happened
Anthropic's AI model Claude Mythos Preview found mathematical weaknesses in cryptographic algorithms that underpin digital security. According to Anthropic, the model developed an improved attack on the post-quantum signature scheme HAWK and a new attack on a reduced version of the Advanced Encryption Standard (AES). Encryption protects nearly everything people do online, and AES is the world's most widely used symmetric encryption standard for digital data.
The model also found the attack on a reduced version of AES-128 almost entirely on its own, according to Anthropic. A researcher built a scaffold that allowed Claude to form hypotheses and test them through experiments. " The method removes one of the guesses an attacker must make and improves on the best previously known attacks by a factor of 200 to 800. Human prompting played a small role.
Why it matters
Anthropic says neither finding affects systems in use today. S. National Institute of Standards and Technology (NIST) and the AES attack applies to a modified version that uses 7 of the full scheme's 10 rounds. Still, the results show how AI models could challenge core assumptions behind internet security. HAWK is one of the remaining schemes in the third round of NIST's competition for additional post-quantum signatures.
These schemes are designed to stay secure even against future quantum computers. Human experts had reviewed HAWK for over two years, but Mythos Preview found an improved attack in just 60 hours, according to Anthropic. The attack exploits a previously undetected symmetry in the mathematical lattice that HAWK's security relies on. Mythos worked semi-autonomously in a multi-agent system to find it.
One agent initially tried to dismiss the idea as infeasible, according to the report, but a second agent found a way to fully exploit it. The human researcher had a background in theoretical computer science but wasn't an expert in lattice-based cryptography, Anthropic says. His role was mostly limited to project management. The API costs totaled about $100,000.
What to watch
" Over three days, the model then generated several hundred million tokens and received only three more substantive prompts, mostly to keep it on track. " This run also cost about $100,000 in API fees for roughly 1 billion tokens. Human researchers who weren't cryptography experts, according to Anthropic, then spent several hundred hours checking the results. S. government and industry partners.
It also coordinated disclosure of the HAWK weakness with the scheme's authors. Mythos Preview remains unavailable to the public. Together with researchers from ETH Zurich, Tel Aviv University, and the University of Haifa, Anthropic also developed a benchmark called CryptanalysisBench that lets others systematically evaluate the cryptanalytic abilities of language models.