Quantum Mines: A New Game-Theoretic Approach to Bitcoin’s Quantum Threat
Cointime reports: Bitcoin Core developer Cory Fields has proposed a novel mechanism called “quantum mines” to address the long-standing threat quantum computing poses to vulnerable Bitcoin addresses. The idea, posted to the bitcoin-dev mailing list, is still a thought experiment and has not been formalized as a BIP, but it offers a fresh perspective on a problem that has largely been framed as a technical migration challenge.
The Mechanism
Under the proposal, anyone attempting to spend BTC from a vulnerable address (such as early P2PK addresses or those with exposed public keys) must first post an equal amount of BTC as collateral from a quantum-safe wallet. The target funds and the collateral are then locked together for a period—say, 30 days. During this window, if the original owner can produce a hidden proof of ownership, they can reclaim their coins and also seize the attacker’s collateral.
The key insight is that the protocol does not require the owner to migrate proactively. Instead, it makes theft financially risky: to steal $100 million, an attacker must first put up $100 million. If caught, they lose it. The odds are designed to deter rational actors.
Pre-Q-Day Commitment
For the mine to work, the owner must plant it before Q-day—the day quantum computers can break private keys. This involves creating a small output from a quantum-safe address that contains a commitment proving the owner knew the private key before Q-day. The commitment does not reveal the key but timestamps the knowledge on-chain. After Q-day, when new validation rules activate, spending from an old address requires equal collateral and a timelock. The attacker cannot tell which addresses are mined, so every attempt carries risk.
Gaps and Extensions
Fields acknowledges that the current framework is designed to catch thieves, but it also burdens honest owners who wish to migrate, as they too must post collateral. He calls for additional rules to exempt honest migrators, though these are not yet specified. One possible extension: owners could simply wait for an attacker to take the bait, then reveal their commitment and claim both their coins and the attacker’s collateral—turning defense into an ambush. Lengthening the lock period (e.g., to a year) would further reduce the attacker’s ability to probe many addresses, as it slows capital turnover.
Comparison with BIP-361
Unlike BIP-361, which mandates migration with a deadline and freezes unclaimed coins, quantum mines offer a collateral-based exit for those who miss the deadline. This is a more property-rights-friendly approach. However, it does not solve the problem of lost keys—including Satoshi’s early holdings—where no owner can reveal a commitment.
Forward-Looking
Regardless of the approach, owners must act before Q-day. After Q-day, proving you knew the private key before the quantum threat is the only valid proof, and that proof can only be established beforehand. The quantum mines proposal shifts the focus from cryptography to game theory, making the cost of attack the design target. It is a promising direction that warrants further exploration, but it also highlights the urgency of preparing for the quantum transition.
