Overview
- Recent technical papers have sharply cut the estimated quantum resources needed to break Bitcoin’s secp256k1 signatures, with a March 2026 Google Quantum AI paper cited for lowering logical‑qubit estimates to the low thousands.
- Analyses published in May 2026 from Citi, Project Eleven and on‑chain researchers put roughly 6.5 to 6.9 million BTC at risk because those addresses have revealed public keys on the blockchain.
- A Quantus report in late May 2026 estimated that 2.3 to 3.7 million BTC are likely inaccessible due to lost keys and therefore cannot be migrated to quantum‑safe addresses, making them permanent targets once quantum attacks are possible.
- No quantum computer today can break Bitcoin encryption, but Project Eleven and other models still place a plausible ‘Q‑Day’ in the early 2030s, and researchers warn adversaries may be quietly collecting public keys now for future decryption.
- Moving to post‑quantum signatures will be complex and slow because Bitcoin requires wide consensus, wallets and hardware‑wallets must change to handle larger schemes, and experts warn a rushed protocol change could create immediate, severe risks; NIST set post‑quantum standards in 2024 and some tech firms have begun phased deployments, which informs possible migration paths.