This Bitcoin Developer’s Idea Would Make Quantum Attacks a Losing Bet

In a November 4 post to the Bitcoin development mailing list, Fields outlined these 'quantum landmines' and two types of auctions designed to turn attacks on vulnerable wallets into expensive gambits. He explicitly called the ideas 'thought experiments,' not a completed Bitcoin upgrade.

The proposal addresses a fundamental threat to Bitcoin's security: the potential arrival of quantum computers powerful enough to break the cryptographic mathematics protecting private keys. Today's computers cannot realistically calculate a private key from its corresponding public key, but a sufficiently powerful quantum computer could use Shor's algorithm to do so.

Researchers call the hypothetical arrival of such a computer 'Q-Day.' No publicly demonstrated machine can steal Bitcoin this way today, and nobody knows exactly when one might exist. The risk varies across different Bitcoin wallet types, as some expose public keys while others keep them hidden until spending.

How Quantum Landmines Work

Fields's quantum landmine system would allow wallet owners to create hidden proofs of ownership before Q-Day. If a thief later uses a quantum computer to recover the private key, they couldn't simply take the coins. Instead, they would need to add an equal amount of their own Bitcoin as collateral from a quantum-safe wallet.

Both coins would enter a restricted output worth twice the original amount. The thief would face a challenge period—30 days in Fields's example—before spending it freely. If the original owner notices the transaction and reveals their pre-Q-Day proof, they could claim the full amount: their original coin plus the thief's collateral.

Auctions for Abandoned Coins

Landmines only work when an owner prepares one before Q-Day and reveals it in time. They cannot protect coins whose keys are already lost, including some early Bitcoin holdings believed to be permanently inaccessible. For these cases, Fields proposes alternative mechanisms.

His staked auction would allow someone to lock up quantum-safe Bitcoin and secretly register a bid against a specific old wallet they expect thieves to target. If an attacker attempts to move coins from an apparently abandoned wallet, a successful challenger could claim part of the attacker's collateral while the vulnerable coins are destroyed rather than awarded to the bidder.

Fields's third idea, a sats auction, requires no advance stake. Instead, a vulnerable-coin spend would trigger a contest where the highest bidder gets the coins minus their bid, while the runner-up pays their bid and gets nothing. This resembles a game where bidders keep raising offers because neither wants to be the person who loses money for nothing.

Implementation Challenges

The system would require significant changes to Bitcoin's infrastructure. Bitcoin would first need quantum-safe ways to hold and spend funds. Wallets would need to support hidden ownership commitments, while Bitcoin's consensus rules would have to enforce collateral, waiting periods, special recovery transactions, and auctions.

Developers would need to agree on activation timing, collateral requirements, and handling of losing bids or leftover funds. Fields believes some mechanics could be introduced through a soft fork, but has not supplied detailed implementation designs. The trade-offs are severe: honest owners might need large collateral deposits, inactive holders could miss their chance to object, and auction rules might accidentally penalize legitimate owners who are simply offline.

None of these protections exists in Bitcoin today. Fields has published no implementation or activation schedule, and his original post leaves auction payouts and even desired outcomes unresolved. The concept remains a theoretical approach to a future threat that may or may not materialize.