Claude Mythos Spent About 60 Hours Finding Crypto Flaws

Claude Mythos spent about 60 hours finding cryptographic weaknesses in the HAWK signature scheme and a deliberately weakened AES variant, per Anthropic researchers.

For teams deciding how much autonomy to give AI systems on research work, this is the number that matters. The model didn't stall on the hard cryptography. It stalled on staying with the problem, and someone had to keep telling it to continue.

Human involvement was mostly encouragement, per the report. Researchers told the model not to give up and to push for publishable quality, not steering the technical work itself.

One caveat: the AES variant Claude found flaws in was deliberately weakened for the exercise, not production AES. That's not evidence real-world AES is at risk. The report doesn't say whether the same persistence holds when nobody checks in at all.

The more interesting read: capability was apparently never the constraint. Someone had to keep the model on task, and that's a much smaller problem to solve than the cryptography itself. Watch whether Anthropic tries the same experiment with zero human check-ins next time.

Anthropic published the account on July 28.