Anthropic says Claude traced NIST ECDSA curve seed origins, easing backdoor fears

Anthropic published a blog post on October 16, 2026, stating that its internal research model Claude traced the origins of the "seeds" for five NIST standard elliptic curves (P-192, P-224, P-256, P-384, and P-521) in under 30 minutes. These seeds define key parameters in the Elliptic Curve Digital Signature Algorithm (ECDSA). Since their inclusion in the standard in 2000, provided by the NSA without explanation, they have sparked long-standing speculation about potential backdoors.

According to Anthropic, Claude found that these seeds were not hashes of hidden phrases but outputs of the C library's lrand48 pseudorandom number generator, initialized with Unix timestamps. The model identified bit patterns, recovered the generator state, and reverse-calculated the generation time to between 1997 and 1998. Specifically, the P-256 standard seed corresponded to the 1,842nd candidate value in one run. The team has released reproducible code.

Anthropic emphasized that this is not a break of ECDSA or a new attack vector, but rather reduces concerns about deliberate backdoors, requiring no action from users. However, the research does not explain all details, including the origin of the B-163 seed, the generation of base points for some curves, and why certain viable candidate curves were skipped.