Europol has urged the cryptocurrency industry to begin preparing for quantum-resistant technology, warning that exposed private-key infrastructure could become a major security weakness as quantum computing advances.

In a report published Wednesday, the European Union’s law enforcement agency said crypto wallets are likely to face greater exposure to future quantum attacks than the blockchains on which those assets exist.

Quantum computers capable of carrying out such attacks are not available today, and Europol did not predict when they could become practical. Instead, the agency said the industry should prepare early, arguing that “proactive adaptation, rather than systemic collapse, is the most likely outcome.”

The agency recommended a phased transition involving wallet upgrades, post-quantum cryptography and cooperation among blockchain developers, miners, exchanges and users.

Bitcoin researchers and institutions are increasingly viewing 2029 as a point by which credible quantum-resistant migration plans should be ready. IBM said in July that it expects quantum computing to begin producing significant commercial revenue over the next two to four years.

Europol’s European Cybercrime Center said a sufficiently powerful quantum computer could potentially derive a private key from a public key and use it to authorize transfers from the associated wallet.

Wallet Security Is the Main Quantum Concern

The report distinguishes between the cryptography protecting a blockchain’s history and the cryptographic systems controlling individual wallets. According to Europol, hash functions used for blockchain security, including Bitcoin mining, are substantially more resistant to quantum attacks than the public-key cryptography used to authorize transactions.

“Cryptocurrencies will not collapse due to quantum computing,” Europol said. The agency’s concern is primarily that attackers could gain control of assets in vulnerable wallets, rather than use quantum computers to rewrite Bitcoin’s blockchain.

The threat is particularly relevant to Bitcoin addresses from its earliest years, known as the “Satoshi era.” Public keys associated with many of these addresses have already been exposed on the blockchain. A sufficiently advanced quantum computer could potentially use those public keys to calculate the corresponding private keys.

About 6.9 million BTC are held in addresses with exposed public keys, according to the report. The figure includes early pay-to-public-key outputs as well as many coins that have remained dormant for extended periods.

Europol said there is no way to eliminate the risk from a public key that has already been exposed. The issue has contributed to ongoing debate within the Bitcoin community over Satoshi-era holdings and whether coins in potentially vulnerable addresses should eventually be frozen as quantum capabilities improve.

Migrating Bitcoin Could Require Significant Block Space

Moving Bitcoin’s existing unspent transaction outputs, or UTXOs, to quantum-resistant technology would itself be a major undertaking. Europol cited a 2024 study estimating that migrating every Bitcoin UTXO could require at least 76 days of cumulative block space.

Allocating 25% of each block to the migration would extend the estimated timeframe to roughly 300 days, according to the study.

Post-quantum cryptography could also increase the amount of data required for transactions. Europol said some new signature schemes are between 10 and 120 times larger than Bitcoin’s existing Elliptic Curve Digital Signature Algorithm, or ECDSA, signatures.

ECDSA is used by Bitcoin to verify ownership and authorize the movement of funds.

For Bitcoin, the challenge is therefore broader than simply developing a quantum-resistant replacement for existing cryptography. The network would need developers, miners, exchanges, wallet providers and users across a decentralized global ecosystem to adopt the new technology before exposed wallets become practical targets for quantum attacks.