EU watchdogs warn quantum computers could threaten blockchains

European financial regulators have issued a warning that future quantum computers could compromise the cryptographic algorithms that protect blockchains, transaction systems, databases and communications.

Quantum risk timeline

The Joint Committee of the European Supervisory Authorities (EBA, EIOPA, ESMA) noted that while current noisy‑intermediate‑scale quantum (NISQ) devices cannot break Bitcoin’s elliptic‑curve signatures, more advanced fault‑tolerant machines could become relevant by the end of the decade. The EU roadmap calls for member states to begin post‑quantum migration by the end of 2026, with high‑risk use cases completed no later than 2030.

Potential exposure of Bitcoin holdings

CryptoQuant founder Ki Young Ju estimated that about 6.89 million BTC may be vulnerable to a future quantum attack, based on a methodology that counts directly visible public keys and coins whose keys could be inferred from spending behavior. Glassnode’s May analysis arrived at a slightly lower figure of 6.04 million BTC (≈30 % of the supply), distinguishing between “structural” exposure (1.92 million BTC) and “operational” exposure.

Bitcoin’s technical response

Developers have drafted BIP‑360 and BIP‑361, which propose new output types and migration policies to reduce long‑exposure risks. Both proposals remain drafts and have not been adopted as consensus rules. The drafts identify Pay‑to‑Public‑Key, reused outputs and Taproot outputs as categories with heightened quantum risk and suggest a future post‑quantum signature scheme for protecting pending transactions.

Industry preparation

Custodians such as Coinbase and hardware wallet maker Ledger are already designing post‑quantum custody solutions that can support multiple signature schemes, acknowledging that migration may take years due to the need to update wallets, custody infrastructure and legacy holdings.

Regulatory focus on “harvest‑now, decrypt‑later”

ESMA highlighted the risk that attackers could collect encrypted data today and decrypt it later once quantum computers become capable, emphasizing the multi‑year planning required for financial systems and blockchains alike.