EU financial watchdogs warn quantum computing poses imminent threat to blockchain encryption

European financial authorities warned that an advanced quantum computer could undermine cryptography used to secure blockchains, saying the threat could emerge before the technology has a viable commercial application.

The warning from the Joint Committee of the European Supervisory Authorities (ESAs), which includes the European Banking Authority (EBA), European Securities and Markets Authority (ESMA) and European Insurance and Occupational Pensions Authority (EIOPA), brings fresh urgency to a long-running question for bitcoin of whether to freeze or not freeze the BTC in legacy wallets. In the event that quantum computers one day do become capable of breaking bitcoin’s cryptography, roughly 6.9 million bitcoin, worth roughly $586 billion, are currently vulnerable, according to Cryptoquant.

“Threats could materialize earlier than any viable commercial application,” the authorities said in their Autumn 2026 Risk and Vulnerabilities report released Wednesday. An advanced quantum computer “could undermine some cryptography systems widely used to secure communications, transactions, databases and blockchains,” according to the report..

Although the report does not mention timelines for quantum computing becoming commercially viable, a recent IBM report says it will be in use in four years or less.

The Satoshi-era bitcoin held in older, legacy addresses or reused addresses could face greater risk if quantum computing advances. In those cases, the public key may already be visible on the blockchain. A sufficiently powerful quantum computer could use it to derive the private key and take control of the coins.

That does not apply equally to every dormant wallet. Many unspent bitcoin outputs still hide the public key behind a cryptographic hash, leaving them less exposed for now. Older pay-to-public-key outputs and reused addressesare different because their public keys are already onchain.

The European Union (EU) warning does not say that a quantum computer capable of breaking bitcoin’s cryptography exists today. But bitcoin cannot simply update its security in the same way a bank does. 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.

The European financial watchdogs said information gathered today could be decrypted later in so-called “harvest now, decrypt later” attacks. The European Commission’s (EC) post-quantum roadmap calls on member states to begin transitioning by the end of 2026, with high-risk use cases to be protected by 2030.