EU watchdogs warn quantum computers threaten blockchain encryption

European financial regulators — the Joint Committee of the European Supervisory Authorities (EBA, ESMA and EIOPA) — warned in their Autumn 2026 Risk and Vulnerabilities report that an advanced quantum computer could undermine the cryptography securing blockchains, and that threats could materialize before quantum computing has a viable commercial application.

Per CryptoQuant, roughly 6.9 million bitcoin (~$586 billion) are currently vulnerable, with older or reused addresses most exposed because their public keys are already visible onchain — a sufficiently powerful quantum computer could derive their private keys. Many unspent outputs still hide their public keys behind a hash and are less exposed for now.

• Bitcoin cannot upgrade like a bank: quantum-resistant signatures would require network-wide consensus, and holders of exposed coins would need to move them first.
• Watchdogs also flagged "harvest now, decrypt later" risks, and the European Commission's post-quantum roadmap calls on member states to begin transitioning by the end of 2026.