Google study shows Bitcoin’s cryptography could fall in minutes, not decades

Google said it verified the results through a zero-knowledge proof — a cryptographic technique that allows third parties to confirm the findings without disclosing the underlying attack methodology, a step the company described as part of a “responsible disclosure” approach.

The Attack Vectors

The paper outlines what it calls an “on-spend” attack: because a wallet’s public key becomes visible on the network the moment a transaction is broadcast — but before it is confirmed on-chain — a sufficiently fast quantum computer could theoretically derive the corresponding private key and reroute funds within that narrow window.

The researchers distinguish between “fast-clock” architectures, such as superconducting or photonic systems, and “slow-clock” architectures, such as neutral-atom or ion-trap systems, noting that only the former would plausibly be fast enough to exploit this window before a transaction settles.

Separately, the paper flags a longer-term risk to dormant or lost wallets whose public keys are already exposed on public ledgers — funds that, researchers say, would become vulnerable to extraction once capable quantum hardware exists, without requiring any action from the wallet owner.

The authors also survey quantum-era risks to smart contracts, proof-of-stake consensus mechanisms and data-availability sampling systems, though the paper stops short of assigning a firm timeline to when any of these vulnerabilities might be practically exploited.

Context and Caveats

Interestingly, industry observers have cautioned against reading the findings as an imminent threat.

The hardware needed to execute such an attack does not yet exist, and independent analysts who reviewed the paper — including commentary from post-quantum security researchers — noted that the estimates describe a theoretical resource floor rather than a demonstrated capability.

Quantum Computing Report and other trade publications framed the study as a recalibration of assumptions rather than evidence of an imminent break.

Even so, the timing has drawn scrutiny. Google has separately set a 2029 internal deadline to migrate its own systems to post-quantum cryptography, a target the company had announced prior to this paper’s release.

The Ethereum Foundation has likewise been developing post-quantum migration plans through a dedicated initiative, mapping out hard forks intended to move the network toward quantum-resistant signatures.

The paper’s authors have urged blockchain communities broadly to accelerate the transition to post-quantum cryptographic standards, while also calling for policy frameworks to address the fate of dormant, quantum-vulnerable holdings — an issue the paper terms “digital salvage” — without creating new avenues for adversarial seizure.