EU Watchdogs Warn Quantum Computers Could Threaten Bitcoin and Blockchain Security

TLDR

• EU financial supervisors have warned that quantum computing could eventually weaken blockchain cryptography.
• No quantum computer capable of breaking Bitcoin or Ethereum security exists today.
• Google researchers sharply reduced estimates for the resources needed to break key elliptic-curve cryptography.
• Bitcoin developers are debating a draft plan to phase out quantum-vulnerable signatures.
• Ethereum is targeting full post-quantum protection across its core network by December 2029.

European financial regulators are warning that advances in quantum computing could eventually threaten the cryptography protecting blockchains and other financial infrastructure.

The European Banking Authority, European Insurance and Occupational Pensions Authority and European Securities and Markets Authority highlighted quantum computing as an emerging technology risk in their Autumn 2026 assessment. The regulators called for stronger preparation as quantum technology advances, alongside risks from AI and cyber threats.

Google Research Raises the Stakes

The concern centers on powerful future quantum computers potentially breaking the mathematical systems used to secure digital signatures. For cryptocurrencies, that could allow an attacker to derive a private key from an exposed public key and authorize transactions.

There is no quantum computer capable of carrying out such an attack today. Current warnings are focused on preparing blockchain networks before sufficiently powerful fault-tolerant machines become available.

Research published by Google Quantum AI and collaborators this year increased the urgency. The team estimated that breaking 256-bit elliptic-curve cryptography could require roughly 1,200 logical qubits, with some modeled systems using fewer than 500,000 physical qubits.

Those estimates represent a major reduction from earlier assumptions. Bitcoin and Ethereum both currently rely on cryptographic systems that could be vulnerable to Shor’s algorithm if sufficiently capable quantum hardware is eventually developed.

Bitcoin and Ethereum Prepare for Quantum Risk

Bitcoin developers are already discussing how the network could migrate. Draft proposal BIP-361, authored by Jameson Lopp and five co-authors, would gradually phase out existing ECDSA and Schnorr signatures after a post-quantum transaction type becomes available.

Under the proposal, sending funds to quantum-vulnerable addresses would eventually be restricted. A later phase, triggered five years after activation, would place additional restrictions on spending coins that had not migrated to quantum-resistant security. The proposal remains a draft and has not been adopted by Bitcoin.

Ethereum has set a firmer internal target. The Ethereum Foundation says it wants Ethereum’s execution, consensus and data layers to be quantum-resistant by December 2029, although the roadmap remains subject to technical changes.

Ethereum has formed a dedicated post-quantum security team and is testing new signature and verification systems. Its official guidance says Ethereum funds are secure today and users do not currently need to take action.

The immediate story is therefore preparation rather than an active attack. The risk for crypto investors depends on how quickly quantum hardware advances and whether blockchain networks can migrate their security systems before existing cryptography becomes vulnerable.