Google Paper Cuts Quantum Attack Resource Estimates, Raising Blockchain Security Urgency

A March 2026 Google Quantum AI paper, co-authored with researchers from the Ethereum Foundation and Stanford, found that Shor's algorithm could break 256-bit elliptic curve cryptography — the basis of Bitcoin and Ethereum wallet security — using roughly 10 times fewer computational resources than previously estimated. The authors used a zero-knowledge proof to validate their findings without publicly releasing the attack circuits, making the results verifiable but not independently reproducible. Experts highlight two distinct threats: a future 'Q-day' when quantum hardware becomes capable enough to break live keys, and the already-active 'harvest-now-decrypt-later' risk, where adversaries collect signed transactions today to decrypt them once hardware matures. Unlike ephemeral web traffic, blockchain transaction data is permanently public, meaning exposed public keys remain vulnerable indefinitely. Wallet infrastructure builders are urged to begin post-quantum migration planning now, regardless of uncertainty around the exact timeline for cryptographically relevant quantum computers.