Quantum Computing Could Threaten Blockchain Security, EU Watchdogs Warn

European financial regulators of finance have issued a warning on September 23 that quantum computing can compromise blockchain cryptography, while Ki Young Ju, founder of CryptoQuant, has estimated that there is public key exposure for 6.89 million BTC for a future quantum attack. The Joint Committee of the European Supervisory Authorities, which includes the European Banking Authority (EBA), the European Insurance and Occupational Pensions Authority and the European Securities and Markets Authority (ESMA), warned that quantum computing may pose significant threats to the security of cryptographic systems protecting transactions, communication, databases and blockchains. 

Financial Sector Urged to Prepare for Post-Quantum Security

The September 23, 2026 risk update did not mention that any existing machine currently breaks Bitcoin cryptography. The warning was based on preparation, mentioning that quantum risks associated with security may come up before commercially viable quantum applications can be developed. The Joint Committee said that quantum computing is a technology that could bring about efficiency in finance, pricing, fraud detection, and compliance. This could be a potential threat to the encryption algorithms currently in use in the financial system. The authorities noted that “risks posed could also materialise faster than any commercially viable application.” 

Another technical report published by ESMA in May analysed the process in greater detail. It said that quantum computers which are advanced enough could use Shor's algorithm to break public key cryptographies such as RSA and Elliptic Curve Cryptography. Bitcoin uses elliptic curve signatures to prove ownership and authorise transactions. ESMA further pointed out that such kinds of attacks are still outside the reach of current noisy intermediate-scale quantum (NISQ) computers. As per ESMA's report, there is no immediate threat from machines that pose danger to cryptography, but the long migration period requires early preparation.

According to Ki Young Ju, the founder of CryptoQuant, around 6.89 million BTC could be at risk of quantum exposure based on his calculations done in February. Out of those, around 1.91 million BTC were linked to visible public keys and other coins with the possibility that their keys had been disclosed due to previous activity on them. The estimate included dormant holdings attributed to early Bitcoin users.

A transition schedule is already established by the European Commission for public bodies and critical infrastructure. The post-quantum transition roadmap requires that all EU countries start adopting post-quantum cryptographic solutions by the end of 2026. Transition in the case of high-risk applications must be completed by the end of 2030. This roadmap was developed as part of the Commission's recommendations issued in 2024 and a joint implementation plan approved in June 2025.

The concerns are also gaining attention as advances in quantum computing continue to challenge earlier estimates of when such attacks could become feasible. According to research conducted by Google, quantum computers may require far less computational power than previously estimated to break encryption. This has raised fresh concerns across the crypto industry, as advances in quantum computing may accelerate the timeline for potential attacks on widely used encryption standards and challenge the long-term security of blockchain-based systems globally.