A new defence concept has emerged to prepare for bitcoin hacking using future quantum computers by forcing attackers to put up their own bitcoin as collateral. Even if a quantum computer reveals the private key of an old wallet, the idea would require extra collateral and an objection process, so a successful hack could instead cause losses.

On Nov. 8, blockchain outlet Decrypt reported that bitcoin developer Cory Fields (코리 필즈) recently proposed "Quantum Mines" and 2 auction methods to the bitcoin developer mailing list. It is still at the thought-experiment stage rather than a finished design for deployment, but it is drawing attention as a new approach to protecting bitcoin wallets that could be vulnerable in the quantum-computing era.

The proposal stems from concerns that quantum computers could neutralise existing cryptographic systems. With conventional computers today, deriving a private key from a public key is effectively impossible, but if a sufficiently powerful quantum computer emerges it could be reverse-calculated using Shor's algorithm. Older bitcoin wallets whose public keys are already exposed could be relatively more at risk.

The core of the Quantum Mines concept is to impose additional costs on an attacker. Before "Q-day", when quantum computers could threaten cryptographic systems, users would pre-register private information in a quantum-safe wallet to prove they were the original owner of the bitcoin. The design would prevent outsiders from confirming whether such information exists.

If an attacker later recovers the private key of an existing wallet using a quantum computer and tries to move 1 BTC, the network would require an additional 1 BTC as collateral. As a result, a total of 2 BTC would be locked under restrictions, and Fields' example provides a 30-day objection period.

If the original owner reveals the pre-registered proof during that period, the network would transfer the existing 1 BTC and the attacker’s 1 BTC collateral, a total of 2 BTC, to the owner’s quantum-safe address. The attacker would lose even their own assets instead of stealing bitcoin.

Another key point is that an attacker cannot know in advance which wallets have Quantum Mines installed. Because the attacker must post additional collateral of the same amount without certainty of success, the explanation is that it could reduce the economic incentive to attack.

The system could also burden legitimate owners. Users trying to move bitcoin from an existing wallet after Q-day could also need to secure collateral of the same amount. Users who do not hold additional bitcoin could face constraints even on moving their assets normally.

Fields also proposed auction methods aimed at vulnerable wallets that have been left untouched for a long time or whose owners are difficult to identify. The first is a pre-deposit auction. Before Q-day, participants would pre-deposit quantum-safe bitcoin and register bids targeting specific vulnerable wallets.

For example, if an attacker targets a wallet holding 50 BTC and tries to move the coins by posting the same 50 BTC as collateral, a participant who bid in advance could raise an objection. In that case, the challenger would take part of the attacker’s collateral, and the coins in the vulnerable wallet would be burned rather than paid to the winning bidder. The goal is to eliminate the profit available from hacking itself.

The second is a "Sats" auction that does not require pre-deposits. If a transfer of vulnerable coins occurs, an auction would open and the highest bidder would take the remaining coins after excluding their bid amount. The runner-up would pay their bid amount and receive nothing. The approach is intended to deter hacking attempts by forcing attackers to bear costs greater than the profits they expected.

There are also many issues to resolve. Quantum Mines would work only if the owner prepares in advance before Q-day, and it would be difficult to apply to coins whose private keys have already been lost. If a user remains offline for an extended period and misses the objection window, there is also a possibility they could lose legitimate assets.

There are fundamental technical limits as well. The bitcoin network cannot distinguish between a valid signature created by a legitimate owner and a signature from an attacker who recovered the private key with a quantum computer. To enforce collateral, objections and auctions in practice, bitcoin’s consensus rules themselves would need to be changed.

This would require quantum-safe wallets and transaction methods, and a technical foundation to support hidden ownership proofs, collateral deposits, waiting periods and recovery transactions. Fields mentioned the possibility of introducing some functions through a soft fork, but did not present specific implementation methods or an activation schedule.

The bitcoin network currently does not have such protection mechanisms in place. This proposal is also closer to an early concept with no implementation code or formal adoption plan. It is meaningful in that it raises the issue that, as advances in quantum computing could threaten the security of existing cryptography, defences should block not only technical attacks but also attackers’ economic gains.