Europol’s Quantum Warning for Bitcoin: Which Wallets Face the Greatest Risk?
Europol said the main risk from future quantum attacks is access to funds in certain wallets, rather than Bitcoin’s transaction history, and called for preparations to transition to quantum-resistant security to begin now.
According to a report published on October 7 by Europol, the European Union’s law enforcement cooperation agency, the network’s transition could take a long time even though no sufficiently powerful quantum computer exists yet. The agency stresses that developers, miners, exchanges, and users need to work together on a phased transition.
Public keys for approximately 6.9 million BTC are visible
The report, cited by CoinDesk, notes that the public keys for approximately 6.9 million Bitcoin are held at addresses visible on the blockchain. Some addresses dating back to Bitcoin’s early years and funds that have not moved for a long time are also in this group.
A quantum computer with sufficient capacity could derive the private key that controls a visible public key. This could enable an attacker to spend the associated Bitcoin. Because a key cannot be made invisible again once it has been exposed, how to protect funds in old wallets is one of the key challenges in the transition.
According to Europol, the hash functions that protect the blockchain’s history and mining processes are more resistant to quantum attacks than the public-key cryptography used to control wallets. For this reason, the agency sees timely security upgrades as a more likely outcome than a collapse of the entire system.
Why should preparations begin now?
Europol says that quantum computers capable of carrying out these attacks do not yet exist and does not give a timeline for when they might emerge. However, moving the funds on the Bitcoin network to new security methods could require a significant amount of block space.
According to a 2024 study cited in the report, converting all unspent transaction outputs—that is, records representing Bitcoin balances that have not yet been spent—to a quantum-resistant format could require at least 76 days’ worth of cumulative block space. If 25% of each block were allocated to this process, the estimated time would extend to approximately 300 days.
New signatures could take up more space
New signatures used in post-quantum security methods can be 10 to 120 times larger than Bitcoin’s current ECDSA signatures. This size difference means the transition also needs to be planned with network capacity in mind.
Europol recommends updating wallets, developing quantum-resistant cryptography, and coordinating among the network’s various participants. The key challenge is not only finding a new method, but also ensuring that the Bitcoin network, which has no central administrator, adopts the change in time.