‘Wow, it’s a real discovery’: Claude cracks a 25-year NSA number mystery

Claude goes digging

Until Claude entered the picture. This month, an Anthropic employee asked an internal research model to investigate, without sharing the old theory that the seeds came from a forgotten phrase.

It took the model less than half an hour to trace five NIST curve seeds to lrand48, a random-number generator found in older C software libraries.

Claude reproduced the sequence behind P-256, a widely used curve, and found an exact match for its published seed at the 1,842nd candidate.

“This is astonishing: it solves the 25-year-old mystery,” the model wrote in its recorded reasoning, after briefly questioning whether it was working inside a simulated test. “Hmm, is it plausible in reality? As of my knowledge … the bounty was unsolved. … All top bits clear—20 bits, chance 1e-6. So indeed real-world.”

“Wow, it's a real discovery.”

Anyone can now rerun the program and get the numbers the NSA supplied. Anthropic says that makes a hidden weakness much less likely, though the team still cannot explain why the program passed over some usable candidates or how other parts of the curves were chosen.

That predictability is what let Claude rebuild the numbers, and it would be a disaster inside a wallet. A secret key generated with lrand48 could be recreated by anyone who worked out roughly when it was made, giving them everything needed to drain the funds.