Blockchain Encryption Faces Quantum Computing Risk, EU Financial Watchdogs Say

European financial regulators have warned that sufficiently advanced quantum computers could eventually compromise the cryptographic technology securing Bitcoin and other blockchain networks, potentially making the threat relevant before quantum computing becomes commercially viable.

The warning has brought renewed attention to Bitcoin’s older addresses, particularly wallets whose public keys are already exposed onchain. If quantum machines eventually become powerful enough to break Bitcoin’s cryptography, those coins could face a higher risk of unauthorized access.

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), highlighted the issue in its Autumn 2026 Risk and Vulnerabilities report.

The regulators said quantum threats could materialize before a viable commercial application for the technology emerges. Their report noted that advanced quantum computers could potentially weaken cryptographic systems used to protect communications, transactions, databases and blockchains.

CryptoQuant estimates that approximately 6.9 million BTC, valued at around $586 billion, could be at risk if quantum computers eventually acquire the ability to break Bitcoin’s cryptographic protections.

The report did not establish a date for when such quantum capabilities could arrive. A recent IBM report, however, suggested that quantum computing could be in use within four years or less.

Bitcoin’s Older Coins Face a Different Risk

BTC held in Satoshi-era wallets and reused addresses may be more exposed because their public keys can already be seen on the blockchain. If a sufficiently capable quantum computer were developed, it could potentially derive the corresponding private keys and allow an attacker to access those funds.

The same vulnerability does not affect every dormant Bitcoin holding. Many unspent outputs continue to hide their public keys behind cryptographic hashes, leaving those coins less exposed under current conditions.

Pay-to-public-key outputs and reused addresses are more concerning because their public keys have already been published directly onchain.

The European regulators did not claim that a quantum computer capable of breaking Bitcoin’s security currently exists. Instead, the warning focuses on preparing for a potential future threat.

Bitcoin’s decentralized governance also makes such a transition more complicated than a conventional software or security update at a financial institution. Implementing quantum-resistant signatures would require consensus across the network, while holders of exposed BTC would need to move their coins before quantum attacks become practical.

Regulators Push Early Preparation

The European authorities also warned about “harvest now, decrypt later” attacks, in which encrypted data is collected today and retained until future technology can potentially decrypt it.

Under the European Commission’s post-quantum roadmap, EU member states are expected to begin transitioning to quantum-resistant systems by the end of 2026. High-risk applications are targeted for protection by 2030.

For Bitcoin, the issue is primarily one of preparation: the network may need to address exposed public keys and transition toward quantum-resistant cryptography before quantum computers reach the capability to exploit them.