EU Regulators Yell "Harvest Now, Decrypt Later" at Quantum's Doorstep

European Union financial supervisors warned Wednesday that advances in quantum computing could undermine the cryptography securing blockchain networks, placing quantum alongside AI-driven cyber risk and private credit on the official systemic risk map. The European Banking Authority, European Insurance and Occupational Pensions Authority and European Securities and Markets Authority issued the warning in an Autumn 2026 Joint Committee Risk Update, flagging "harvest now, decrypt later" scenarios in which attackers hoard encrypted data today for decryption once quantum machines mature. The specific concern covers quantum algorithms capable of breaking the public-key cryptography that protects transactions, communications and databases across the financial system.

The warning follows a March assessment from Google Quantum AI researchers, who estimated that breaking the cryptography used by many cryptocurrencies could require about 20 times fewer physical qubits than earlier estimates. A qubit is the basic unit of a quantum computer. No computer capable of carrying out such an attack exists today. For cryptocurrency holders, the concern is that a future quantum computer could derive a private key from an exposed public key and use it to authorize transactions, potentially draining wallets whose owners did not migrate to post-quantum signature schemes.

Bitcoin ($BTC) developer Jameson Lopp and five co-developers proposed in February to phase out the network's current signatures and restrict how unmigrated funds could be spent five years after the proposal's activation. That proposal has not been adopted. The Ethereum Foundation has set a target of December 2029 to make Ethereum ($ETH) resistant to quantum attacks across its execution, consensus and data layers. StarkWare has tested a quantum-resistant Bitcoin transaction on mainnet, demonstrating a concrete step toward hardening $BTC infrastructure against future cryptographically relevant quantum computers.