On October 16, 2026, Anthropic said an internal Claude research model worked out, in under half an hour, how the NIST elliptic curves used by ECDSA were generated, a puzzle that had stood for almost 30 years. Those curves sign many HTTPS certificates. It is not a vulnerability, and your website does not need any change.
What we know
- The puzzle: curves P-192, P-224, P-256, P-384 and P-521 come from "seeds" that, according to Anthropic, the NSA supplied with no explanation. NIST adopted them in 2000 in the FIPS 186-2 Digital Signature Standard.
- The old theory: the most popular explanation was that the seeds came from a phrase run through a hash function, a rumor linked to Jerry Solinas, a longtime NSA employee. Anthropic says it was wrong: none of the seeds came from a hash.
- What Claude found: asked by an Anthropic employee, the model guessed that a 1990s random number generator had been used and wrote a scanner to detect it. According to the post, the seeds come from the C library's `lrand48` generator, seeded with the computer clock, at dates from May 1997 to April 1998.
- How long it took: Anthropic says "in under half an hour." It does not name the model and calls it "an internal research model."
- Still unexplained: the seed of binary curve B-163 and the base points of P-224, P-256, P-384, P-521 and the binary curves. Nor is it known why candidate 1842 was picked for P-256 over candidate 876, which also gave a valid curve.
- The bounty: in October 2023, cryptographer Filippo Valsorda launched a $12,288 bounty for the seed origins, tripled if donated. Anthropic says the $36,864 will go to the Internet Security Research Group, the nonprofit behind Let's Encrypt.
What changes and what doesn't
The curves are as safe as before. Anthropic puts it plainly: "This is not a cryptographic break, new attack, or weakness." It adds that there is nothing to do differently. The authors argue the finding makes a hidden backdoor much less plausible, because the seeds come from a simple, reproducible process.
What changes is what we know about AI. A model solved, in minutes, an open cryptography puzzle that had carried a public bounty since 2023. That says something about what these models can already do with code; it says nothing about what the public version of Claude will do.
How to check your site
- See which key your certificate uses. In Chrome, open your site, click the icon at the left of the address bar and open the certificate details. In the details tab, look for the public key algorithm: you will see an elliptic curve key (usually P-256 or P-384) or an RSA key.
- If it is ECDSA, do nothing because of this news. There is no need to change certificate or curve. If someone offers to "migrate your HTTPS" citing this finding, ask for the specific flaw: Anthropic says there is none.
- Watch what does break HTTPS: automatic renewal that runs on time, coverage for every subdomain, and a server that refuses old TLS versions.
- If you use AI to review code or configuration, this case shows it can spot in minutes patterns people missed for decades. Use it to review, and have a person check the result before applying it.
Related: Let's Encrypt Cuts Certificates to 64 Days: What to Check
Sources
- Anthropic, "Claude reveals ECDSA curve origins," October 16, 2026
- Filippo Valsorda, NIST curve seeds bounty, October 5, 2023
Updates: if NIST or an independent researcher confirms or qualifies the finding, it will be added here with a link.