Bitcoin’s quantum risks are a governance, not engineering, problem

Digital asset manager Grayscale backed accelerated efforts to make public blockchains quantum-resistant in a new research note arguing the technical solutions already exist but the harder challenge is getting decentralized communities to agree on implementing them.

“Public blockchains do not have CTOs; they are global communities governed by consensus,” wrote Zach Pandl, Grayscale’s head of research. “The potential threat to digital security from quantum therefore presents both a challenge and an opportunity.”

The note follows a week of intensive industry response to Google Quantum AI’s paper, which found that breaking bitcoin’s BTC$69,132.12 elliptic curve cryptography would require fewer than 500,000 physical qubits, roughly a 20-fold reduction from previous estimates, and could be executed in approximately nine minutes once the machine is primed.

CoinDesk’s analysis of the paper found that the attack gives an attacker a roughly 41% chance of stealing funds before a bitcoin transaction confirms.

Pandl highlighted four takeaways from the Google research that Grayscale found persuasive. Progress toward a cryptographically relevant quantum computer may come in “discrete jumps” rather than linearly, making timelines unpredictable.

The technical solutions, specifically post-quantum cryptography, are mature and already securing internet traffic and certain blockchain transactions. Quantum risk varies significantly across blockchains depending on their transaction model, consensus mechanism, and block time.

From a pure engineering standpoint, Pandl argued bitcoin has lower quantum risk than other chains because it uses a UTXO model, proof-of-work consensus, no native smart contracts, and certain address types that are not quantum-vulnerable if not reused after spending.

The harder question is what to do about the roughly 6.9 million BTC sitting in wallets where public keys are already permanently exposed on the blockchain, including an estimated 1 million believed to belong to pseudonymous creator Satoshi Nakamoto.

Binance co-founder Changpeng Zhao raised the same question last week, saying that if Satoshi’s coins move during a migration “it means he is still around, which is interesting to know,” and that if they don’t move “it might be better to lock or effectively burn those addresses.”

Grayscale frames the options similarly — burn them, do nothing, or deliberately slow their release by limiting the rate of spending from vulnerable addresses — but noted that the bitcoin community has a history of contentious debates over protocol changes, pointing to last year’s dispute around image data stored in blocks.

The contrast with Ethereum is worth noting.

CoinDesk reported last week that Google’s paper identified five separate attack vectors against Ethereum worth over $100 billion in combined exposure, spanning account keys, admin keys on stablecoins, smart contract code, consensus mechanisms, and data availability.

Ethereum Foundation researcher Justin Drake, who co-authored the Google paper, estimated at least a 10% chance of a quantum key recovery by 2032. The foundation has been staking aggressively, putting $93 million of ether into validators in a single day last week, but has not publicly addressed quantum migration timelines.