EU watchdogs warn quantum computers could threaten blockchain encryption before commercial use
EU supervisors flag quantum risk to blockchain cryptography
European financial regulators said an advanced quantum computer could undermine the cryptography that protects blockchains, the shared digital records that track crypto transactions. They warned the risk could appear before quantum computing has any working commercial use.
The warning came from the Joint Committee of the European Supervisory Authorities (ESAs), which includes the European Banking Authority, the European Securities and Markets Authority and the European Insurance and Occupational Pensions Authority.
It was published in the group's Autumn 2026 Risk and Vulnerabilities report, released Wednesday. The report does not say that a quantum computer able to break bitcoin's cryptography exists today.
Key points from the warning
- About 6.9 million bitcoin, worth roughly $586 billion, are currently vulnerable if quantum computers one day become powerful enough to break bitcoin's cryptography, according to Cryptoquant.
- Older or reused bitcoin addresses are the most exposed, because their public keys may already be visible on the blockchain.
- Many dormant bitcoin holdings are less exposed for now, because their public keys are still hidden behind a cryptographic hash.
- Bitcoin cannot upgrade its security the way a bank can, and a change to quantum-resistant signatures would need network-wide agreement.
What the ESAs report says
The authorities wrote that "threats could materialize earlier than any viable commercial application." An advanced quantum computer "could undermine some cryptography systems widely used to secure communications, transactions, databases and blockchains," the report said.
The watchdogs also said information gathered today could be decrypted later, in what are known as "harvest now, decrypt later" attacks.
Where the 6.9 million bitcoin figure comes from
The estimate that roughly 6.9 million bitcoin are vulnerable is attributed to Cryptoquant, not to the European regulators.
A recent IBM report says quantum computing will be in use in four years or less. The ESAs report itself does not mention timelines for quantum computing becoming commercially viable.
What is still unclear
The report does not say when a quantum computer capable of breaking blockchain cryptography might exist, or how likely that is. The only timeframe in the supplied material comes from IBM's separate report.
Why exposed bitcoin addresses are the main concern
Older pay-to-public-key outputs and reused addresses are different from most dormant wallets, because their public keys are already on the blockchain. In those cases, a sufficiently powerful quantum computer could use the public key to derive the private key, the secret code that controls the coins, and take control of them.
Most unspent bitcoin outputs still hide the public key behind a cryptographic hash, which leaves them less exposed for now.
What happens next
The European Commission's post-quantum roadmap calls on member states to begin transitioning by the end of 2026.
For bitcoin, moving to quantum-resistant signatures would require network-wide consensus, and holders of exposed coins would need to move them before such an attack becomes possible.
Sources
Newisty Editorial Team covers technology, cryptocurrency, digital products, online platforms, developer tools and the wider digital economy. Our content is researched from official sources, company announcements, public documentation, market data and other primary or reputable sources. Articles are reviewed and edited before publication for clarity, accuracy and useful context.