Claude cracks the 25-year-old NIST ECDSA seed mystery in under 30 minutes: just lrand48 seeded by Unix timestamps
Anthropic Research · rss · 2026-10-16
Anthropic's Frontier Red Team reports that Claude solved a decades-old cryptographic mystery in under half an hour: the origin of the seeds behind NIST's standard elliptic curves (P-192 through P-521), which the NSA provided in 2000 with no explanation, fueling years of backdoor speculation and an amateur bounty hunt.
How Claude did it
- Instead of chasing the rumored "hash of a funny passphrase" (a lead that dead-ended after NSA's Jerry Solinas died in 2023), Claude hypothesized the generator used a weak 1990s C-library PRNG and wrote a scanner testing 34 generator/slice combinations;
- It spotted that in 4 of 10 seeds, all 20 32-bit words had a zero top bit (1/5810 by chance) — the signature of lrand48;
- It recovered hidden state bits by brute force and used LLL lattice reduction to solve the truncated linear congruential generator, finding all ten prime-curve seeds matched lrand48() >> 23;
- Rolling the PRNG state back, every initialization was a Unix timestamp between May 1997 and April 1998 (binary-curve ones doubled to April 17, 1998).
What it means
- The seeds were never a hash — just lrand48 seeded by the clock, now reproducible by anyone;
- No cryptographic break; quite the opposite, this makes deliberate backdoors far less plausible;
- Claude also traced some curve base points, including six from Arjen Lenstra's FreeLIP RNG.
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