Anthropic says Claude identified how the unexplained seed values behind major NIST elliptic-curve cryptography standards were generated. In under half an hour in October 2026, an internal research model determined that seeds for NIST P-192, P-224, P-256, P-384 and P-521 were outputs of the legacy C-library lrand48 pseudorandom-number generator initialized with Unix timestamps, rather than hashes of secret phrases or other cryptographic algorithms. NIST adopted these curves in 2000 for the FIPS 186-2 Digital Signature Standard, while the NSA had supplied their seed values without explaining their provenance. Anthropic reconstructed timestamps from May 1997 through April 1998 and the candidate positions that reproduce ten prime-curve and binary-curve seeds; P-256, for example, was the 1,842nd 20-byte candidate from its run. Anthropic says the result is not a cryptographic break or a newly discovered weakness, and that the simple reproducible process makes intentional backdoors less plausible. Claude also traced base points for P-192 and five ANSI X9.62 example curves to the FreeLIP random-number generator, but could not explain base points for P-224, P-256, P-384, P-521 or NIST binary curves. B-163 remains unexplained. Anthropic will donate the $36,864 NIST elliptic-curve seeds bounty to the Internet Security Research Group.

Anthropic's LLM Claude Mythos has discovered key-recovery attacks on HAWK, a post-quantum signature scheme candidate. While the attack is impractical for most versions of HAWK, it significantly reduces the security of the toy version HAWK-256, which has 64-bit security that is nearly breakable.

Researchers at Anthropic have utilized Claude Mythos Preview to uncover vulnerabilities in cryptographic algorithms. One attack significantly compromises the HAWK digital signature scheme, while another reveals a new method to exploit round-reduced AES, a widely used symmetric cipher.

AI auditor zkao identified a critical soundness bug in OpenVM's zkVM guest library openvm-pairing, allowing a malicious prover to forge any pairing equality. This vulnerability does not affect the zkVM's proving system itself but impacts code relying on the flawed library.

Secret NSA documents reveal that the agency promoted the Data Encryption Standard (DES) in the 1970s despite knowing its vulnerabilities to eliminate competition. The NSA also exploited export-law exceptions in the 1990s to favor RC4 and RSA-512, compromised random number generator standards, and maintained a substantial budget to influence security standards through the 2010s.