Bitcoin Developer Proposes Quantum Landmines to Stop Wallet Theft

Bitcoin developer Cory Fields has proposed an unusual approach to defending against future quantum computer threats by forcing potential thieves to risk their own funds. In a post to the bitcoin developer mailing list, Fields shared conceptual mechanisms designed to turn unauthorized wallet access into a costly gamble rather than a guaranteed payday.

The discussion centers around the hypothetical arrival of a sufficiently powerful quantum computer capable of running Shor's algorithm to calculate a secret private key from a known public key. While today's machines cannot perform this feat, some older and specific newer Bitcoin formats expose public keys, creating a potential future vulnerability known as researchers as Q-Day.

To counter this, Fields suggested three thought experiments that do not yet represent a completed software upgrade. The first concept involves quantum landmines, where a wallet owner creates a tiny, separate quantum-safe output containing a hidden proof of ownership established before Q-Day. If a future attacker uses a quantum computer to recover the old key and attempts to move the funds, they would be forced to add an equal amount of their own collateral from a quantum-safe wallet.

Both the stolen coin and the collateral enter a restricted output subject to a waiting period. The legitimate owner can then reveal the pre-Q-Day proof to claim the combined total, turning the attempted theft into a significant financial loss for the attacker. However, this system also presents trade-offs, as owners needing to move legacy coins would also require matching collateral, and inactive holders could miss their chance to protect their assets.

Quantum landmines and auctions could force future thieves to post collateral before accessing vulnerable wallets.

Bitcoin Developer Ideas for Quantum Security

Fields also proposed two auction-based mechanisms. A staked auction would allow users to lock up quantum-safe Bitcoin and register a bid against a specific legacy wallet in advance. When an attacker tries to move the funds and posts collateral, a challenger can claim part of that collateral while the original vulnerable coins are destroyed. A third idea, a sats auction, triggers a contest during a spend attempt where the highest bidder receives the coins minus their bid, and the runner-up loses their bid entirely.

Implementing these ideas would require significant changes to Bitcoin, including quantum-safe holding methods, hidden ownership commitments, and consensus rules capable of enforcing collateral, waiting periods, and auctions. Developers would also need to reach a consensus on activation rules and collateral requirements.

Why it matters

These theoretical mechanisms highlight the complex trade-offs developers face in securing legacy cryptocurrency against future technological advancements. While strict migration deadlines could permanently lock out inactive owners, introducing penalty-based systems risks creating barriers for legitimate users who lack spare collateral.