EU financial watchdogs warn quantum computing poses imminent threat to blockchain encryption
European financial regulators warned that sufficiently advanced quantum computers could break cryptographic protections used by blockchains, putting an estimated 6.9 million bitcoin—about $586 billion—at risk. The Joint Committee of the European Supervisory Authorities said the threat could emerge before quantum computing has a clear commercial application and urged preparedness for post-quantum transitions.
Why It Matters
The advisory highlights an urgent operational and policy problem for Bitcoin and other blockchain systems: coins whose public keys are already revealed onchain may be vulnerable to future cryptanalytic attacks, and replacing blockchain cryptography would require coordinated, network-wide action. The European Commission has also set timelines for member states to begin post-quantum migration steps by end-2026.
Key Facts
- Issuing body: Joint Committee of the European Supervisory Authorities (EBA, ESMA, EIOPA)
- Report: Autumn 2026 Risk and Vulnerabilities report
- Estimated vulnerable bitcoin: 6.9 million BTC (~$586 billion according to CryptoQuant)
- At-risk address types: Older Satoshi-era legacy addresses and reused addresses with public keys exposed onchain
- EU post-quantum timeline: Member states urged to begin transitions by end of 2026; high-risk cases to be protected by 2030
European financial supervisors cautioned in a joint Autumn 2026 report that advanced quantum computing capabilities could one day compromise cryptographic algorithms that secure blockchains. The Joint Committee of the European Supervisory Authorities — comprising the EBA, ESMA and EIOPA — said such a development might materialize before quantum technology reaches a widely usable commercial form, creating risks for stored digital assets and transaction security.
Regulators pointed to Bitcoin as particularly exposed in some cases because certain legacy and reused addresses have public keys already published on the blockchain. If a quantum computer becomes powerful enough, it could derive corresponding private keys from those public keys and transfer control of the coins. CryptoQuant estimates about 6.9 million BTC currently sit in addresses that could be vulnerable under that scenario, a figure regulators highlighted in the report.
Not all dormant bitcoin are equally at risk: many unspent outputs still conceal public keys behind cryptographic hashes, which provides more protection for now. But the warning underscores that shifting Bitcoin to quantum-resistant signature schemes would not be a simple software patch; any such migration would require consensus across the network and proactive movement of exposed coins before an effective cryptanalytic attack appears.
The report also flagged the danger of "harvest now, decrypt later" strategies, where encrypted information collected today could be stored and decrypted once quantum capabilities advance. The European Commission’s post-quantum roadmap complements the regulators’ assessment by urging member states to start transitioning by the end of 2026 and to safeguard high-risk use cases by 2030. The ESAs did not state that a quantum computer capable of breaking blockchain cryptography currently exists; a recent IBM report referenced in the article suggested commercial use of quantum computing could arrive within four years or less, but the regulators focused on preparedness rather than current occurrence.
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