Europol: quantum threat targets exposed crypto keys, not blockchains

Europol's European Cybercrime Centre published a report on quantum computing and cryptocurrencies, arguing that wallets with exposed public keys — not blockchains themselves — are the primary point of exposure to a future quantum attack. No quantum computer capable of such attacks exists yet, and Europol did not predict when one will, but it urged developers, exchanges and users to begin a phased post-quantum migration now through wallet upgrades, post-quantum cryptography and industry-wide coordination.

• About 6.9 million bitcoin sit at addresses with exposed public keys, including Satoshi-era and long-dormant wallets whose private keys a sufficiently powerful quantum computer could derive.
• Europol said "cryptocurrencies will not collapse due to quantum computing," since the hash functions securing chain history are far more resistant than the public-key cryptography controlling wallets.
• The harder task is coordination: quantum-resistant signatures can be 10 to 120 times larger than ECDSA, and migrating every bitcoin UTXO could require months of block space.