Anthropic says Claude helped reconstruct P-256 seed for Ethereum passkey security

Anthropic said on Oct. 16 that Claude had helped reconstruct the public seed behind P-256, a NIST-standardized cryptographic curve supported for Ethereum passkey signing. The finding gives wallet builders new evidence about longstanding concerns over the curve's origins. A public seed is a design input used to derive a coefficient in the curve's equation. The public seed is separate from private signing credentials that authorize wallet activity.

Anthropic says unexplained seeds supplied by the U.S. National Security Agency had fueled suspicion about deliberately weakened parameters. Anthropic's published recipe initializes the old C-library generator lrand48 with the timestamp for Aug. 16, 1997, at 01:52:34 UTC. The generator produces a sequence of candidate seeds. Advancing to candidate 1,842 returns the published P-256 value, providing a repeatable recipe for that public constant.

Anthropic says the finding makes deliberate backdoors less plausible. Anthropic describes no new attack or curve weakness and says users need take no action.

Ethereum's EIP-7951 specifies verification of signatures using P-256, also called secp256r1. EIP-7951 names Apple Secure Enclave, Android Keystore and FIDO2/WebAuthn devices as relevant hardware. This connects wallet authorization with signing capabilities built into devices and authenticators. EIP-7951's motivation lists device-native signing, multifactor authentication and simpler key management as uses for account abstraction.

Ethereum's account documentation distinguishes private keys that sign transactions from public information used to verify transactions. Contract accounts are controlled by code. EIP-7951's P256VERIFY operation takes a message hash, a signature and a public key, then checks the signature's validity. P-256 differs from secp256k1, the curve already used in Ethereum. The finding is relevant to P-256-compatible signing, rather than every Ethereum wallet.

Anthropic reports that candidate 876 also yielded a prime-order curve of the required size, leaving selection criteria unclear. The number of generation runs remains unknown. The origin of P-256's base point, a separate fixed mathematical point, also remains unknown.