Updated

Updated · CoinDesk · Jul 27

Google Cuts Crypto-Breaking Qubit Estimate 20-Fold as White House Sets 2028 and 2030 Quantum Goals

Updated

Updated · CoinDesk · Jul 27

Google Cuts Crypto-Breaking Qubit Estimate 20-Fold as White House Sets 2028 and 2030 Quantum Goals

Q: Are exposed Bitcoin addresses and lost coins the real weak link in a 2029 quantum attack scenario?

Yes. In a 2029-style quantum attack scenario, the weakest link is likely to be Bitcoin whose public keys are already exposed on-chain, especially old P2PK outputs, reused addresses, and coins that cannot be moved because the keys are lost. That is because Shor’s algorithm would not need to break Bitcoin’s hashing or mining first. It would target signatures by deriving a private key from a known public key. For many modern addresses, the public key stays hidden until spending, which narrows the attack window. But for legacy P2PK outputs, reused P2PKH/P2WPKH addresses, and Taproot outputs, exposure can already exist at rest. Multiple recent analyses put the exposed share at roughly 25% to 35% of supply, with around 1.7 million BTC in old P2PK alone and several million more tied to address reuse. Lost or dormant coins matter because they are effectively unmigratable. If their public keys are known, no owner can move them to a post-quantum format before an attacker does. That makes them a standing target and a likely early proof point if a cryptographically relevant quantum computer appears. But exposed coins are not the only risk. Even coins in safer address types become vulnerable during spending, because the public key is revealed in the transaction flow and could be attacked in the mempool if a quantum machine is fast enough. So the immediate weak link is exposed and possibly lost coins, while the broader systemic risk is Bitcoin’s slow governance and migration process.

1 articles · Updated · CoinDesk · Jul 27

Fewer than 500,000 physical qubits could crack the elliptic-curve cryptography used by bitcoin and ether, according to Google researchers, pulling some Q-Day estimates forward to 2029.
The White House has set a 2028 target for a powerful quantum computer and a 2030 deadline to move high-value assets and federal data to post-quantum cryptography, adding urgency to migration plans.
Bitcoin may face the first visible stress because its decentralized governance can slow upgrades: researchers and Deutsche Digital Assets say major protocol changes require roughly 90% miner consensus, unlike banks that can act by management decision.
The threat is not a single cutoff date but a gradual one, since attackers would only need enough quantum power to decrypt signatures or data before the targeted funds or information lose value.
That makes crypto a likely early warning system for wider financial infrastructure, because the same quantum capability that could break blockchain signatures would also threaten bank encryption.