Bitcoin has faced many risks since its launch, from exchange failures and hacks to market crashes and changes in regulation. Now, European financial regulators have raised a different kind of concern. The risk comes from a technology that does not pose a direct threat to Bitcoin today but could create a major problem in the future: quantum computing.
European financial watchdogs have warned that powerful quantum computers could one day break some of the cryptography that protects blockchains. Their warning says this risk could arrive before quantum computers have a clear commercial use. That point has drawn fresh attention to the security of Bitcoin and other digital assets.
The issue matters because Bitcoin relies on cryptography to prove who has the right to spend coins. If a future quantum computer becomes powerful enough, it could weaken part of that protection. Around 6.9 million Bitcoin, worth about $586 billion, could be exposed under current conditions, according to data cited by CoinDesk.
This does not mean $586 billion in Bitcoin is at risk of theft today. No quantum computer that can carry out such an attack exists at present. The concern is about what could happen if the technology reaches that level in the future.
What European Regulators Said
The warning came from the Joint Committee of the European Supervisory Authorities. This group includes the European Banking Authority, the European Securities and Markets Authority, and the European Insurance and Occupational Pensions Authority.
In its Autumn 2026 Risk and Vulnerabilities report, the group said advanced quantum computers could undermine cryptographic systems that protect communications, transactions, databases and blockchains. The authorities also said the risk could appear before quantum computing has a commercially useful application.
That message is important because it changes the way the industry may need to think about the problem. Bitcoin does not have to wait until quantum computers become common. The network may need to prepare before that point.
A bank can change its security system through a controlled software update. Bitcoin is different. It has no central company that can simply replace its security rules for everyone. Any major change requires agreement across the network.
Why Quantum Computers Matter
A normal computer uses bits. A bit can hold a value of zero or one. A quantum computer uses quantum bits, or qubits, which can work with information in a very different way.
This technology can solve some types of problems much faster than traditional computers. It is still at an early stage, but researchers continue to improve quantum machines and the methods used with them.
Bitcoin uses public-key cryptography as part of its security system. A wallet has a private key and a public key. The private key must remain secret because it gives control over the coins. The public key can be shared when needed.
The concern starts when a public key is visible on the blockchain. A powerful enough quantum computer could, in theory, use that public key to work out the private key. If that happened, an attacker could gain control of the related Bitcoin.
This is not a simple computer hack. It would require a quantum machine with capabilities far beyond anything available today.
Older Bitcoin Addresses Face More Risk
Not all Bitcoin has the same level of exposure to this possible threat.
Some older Bitcoin addresses have public keys that are already visible on the blockchain. The same can happen when an address is reused. These coins could face greater risk if quantum technology becomes powerful enough.
Bitcoin has other types of addresses where the public key remains hidden behind a cryptographic hash until the owner spends the coins. Those coins are less exposed under the current model.
This difference explains why the number of 6.9 million BTC matters. It does not mean every Bitcoin could become vulnerable at the same time. Instead, the figure refers to coins held in structures that may give a future attacker a clearer path to the private keys. CoinDesk cited CryptoQuant for the estimate of about 6.9 million BTC, with a value of roughly $586 billion.
Satoshi-Era Coins Draw Attention
Some of the most discussed coins are Bitcoin from the early years of the network. These coins sit in older addresses and, in some cases, have not moved for many years.
If a powerful quantum computer appears, dormant coins with exposed public keys could become attractive targets. An attacker would not need the owner to make a mistake. The attacker could try to use the weakness in the underlying cryptography.
This creates an unusual problem for Bitcoin. Some old coins have owners who are known only through blockchain addresses. Others may belong to people who have lost their private keys. Some could also belong to people who are simply waiting and have no plans to move their coins.
A future security upgrade would therefore have to deal with more than technical code. It could also create difficult questions about how the network should treat coins that remain in vulnerable addresses.
Bitcoin May Need Network-Wide Agreement
Bitcoin cannot solve this issue through one company or one regulator. A change to the network’s signature system would require broad agreement among the people and groups that maintain, use and support Bitcoin.
That could include developers, miners, exchanges, wallet providers, businesses and users.
The network would also need to give holders a way to move vulnerable coins to safer addresses before a quantum attack becomes practical.
That sounds simple in theory, but it could become very difficult in practice. Some Bitcoin holders may not have access to their private keys. Others may not act before a deadline. There may also be disagreement over what should happen to coins that remain in vulnerable addresses.
This is why the quantum issue is more than a technology problem. It could become a question about how Bitcoin handles ownership and security at the network level.
Europe Wants Early Preparation
The European regulators did not say that a quantum attack on Bitcoin is about to happen. They also did not give a specific date for when such computers will become powerful enough to break current blockchain security.
Instead, their message focused on preparation.
The European Commission’s post-quantum roadmap calls for member states to start their transition toward post-quantum security by the end of 2026. It also calls for high-risk use cases to have protection by 2030.
The goal is to avoid a situation where organisations wait until quantum computers become powerful and then try to fix everything at once.
The financial sector has a strong reason to take this approach. Banks, payment systems and digital asset networks all depend on cryptography. A security change could take years if it affects a large number of users and systems.
The “Harvest Now, Decrypt Later” Problem
Another concern from the European regulators is known as “harvest now, decrypt later.”
The basic idea is simple. An attacker could collect encrypted information today and keep it until a future quantum computer becomes powerful enough to decrypt it.
This idea is more relevant to some forms of encrypted data than to Bitcoin itself, but it shows why regulators want early action.
Data that appears safe today may not remain safe forever if the technology used to protect it becomes weak.
For Bitcoin, the issue is slightly different because blockchain records are public. The main concern is not that someone will decrypt today’s private Bitcoin transactions years later. The concern is that future technology could use information already visible on the blockchain to attack exposed keys.
A Possible Solution Is Already Under Test
There is also some positive news.
On September 24, 2026, StarkWare reported progress on a method designed to help create quantum-resistant Bitcoin transactions. The work used AI-assisted coding to improve the speed of a computation needed for the process.
The estimated computing cost fell from about $320 to $66, according to StarkWare’s research. The earlier $320 estimate came from a Bitcoin transaction mined in August. That test required about 3,100 hours of computing time across roughly 100 graphics processors.
The new $66 figure, however, is still an estimate. It has not yet been demonstrated through another transaction mined on Bitcoin.
That detail matters. The research shows that the cost may fall as the method improves, but it does not prove that a cheap, large-scale solution is ready for Bitcoin users.
The New Method Has Limits
The StarkWare method also has several limits.
For one, it requires transactions to go directly to a miner rather than travel through the Bitcoin network in the usual way. It also cannot protect coins whose public keys are already exposed in the way that creates the main quantum risk.
So, while the research offers another possible tool, it does not remove the need for a wider Bitcoin solution.
Still, the reduction from $320 to $66 shows how quickly costs can change when researchers improve the underlying process. More research could reduce those costs further.
Bitcoin Does Not Face the Threat Today
The most important point is that Bitcoin is not under a quantum attack today.
No known quantum computer can break Bitcoin’s current cryptography. The European warning is about a possible future threat, not a present failure of the Bitcoin network.
That difference is important for anyone who owns BTC.
The $586 billion figure should not be read as money that could suddenly disappear. It represents an estimate of Bitcoin that could be vulnerable if a sufficiently powerful quantum computer becomes available and the affected coins remain in their current form.
There is no evidence that such a machine can steal Bitcoin today.
Why the Warning Still Matters
Even though the threat is not immediate, Bitcoin has to consider it well before the technology becomes powerful enough to cause damage.
Security upgrades take time. Users need time to understand them. Wallet companies need time to add support. Exchanges need time to test new systems. Developers need time to agree on network changes.
Bitcoin also has a large amount of value at stake. A mistake during a major security transition could have serious consequences for users.
The European warning therefore adds pressure for the crypto industry to study the issue early rather than wait for a crisis.
What Could Happen Next
The next stage is likely to involve more research into quantum-resistant cryptography and possible changes to Bitcoin’s signature system.
Developers will need to examine how users can move exposed coins to safer addresses. They will also need to consider what happens to coins whose owners do not act.
At the same time, researchers will continue to track progress in quantum computing. If quantum machines become more powerful, the estimated timeline for the threat could change.
For now, there is no confirmed date for a quantum attack on Bitcoin. There is also no agreement on a final network-wide solution.
A Long-Term Security Question
The latest warning from European regulators does not mean Bitcoin is broken. It shows that the network faces a security question that may become more important as computer technology improves.
About 6.9 million BTC, worth roughly $586 billion, could be vulnerable under the conditions described by the latest analysis. Older and reused addresses face particular concern because their public keys may already be visible.
At the same time, research from StarkWare suggests that new methods for quantum-resistant Bitcoin transactions may become cheaper and more practical. Its latest estimate cuts the computing cost from about $320 to $66, although the lower figure has not yet been confirmed through another mined Bitcoin transaction.
The central issue is therefore not whether Bitcoin can be protected. It is how early the network can prepare, how quickly researchers can improve the available tools, and whether Bitcoin users can move vulnerable funds before quantum computers reach the required level.
For now, the technology remains a future risk rather than a current attack. But the message from European regulators is clear: preparation needs to start well before the threat becomes real.
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