Bitcoin developer proposes 'landmines' to make quantum thieves risk their own BTC
Quantum 'landmines' proposed for vulnerable bitcoin
Cory Fields, a Bitcoin Core developer at MIT's Digital Currency Initiative, proposed a way to make future quantum thieves risk their own bitcoin before they can steal anyone else's. He outlined the idea on Wednesday in a post to the bitcoin-dev mailing list.
The idea is called "quantum landmines." A sufficiently powerful quantum computer could calculate a wallet's secret spending key from its public key. A wallet is a place where crypto is held, and the key is what allows spending.
Some early bitcoin payments exposed public keys from the start. Coins associated with Bitcoin creator Satoshi Nakamoto are among the potential targets mentioned in the report.
Main points at a glance
- An attacker trying to move vulnerable bitcoin would need to put up matching collateral from a quantum-safe wallet.
- Both the target coins and the attacker's collateral would be locked for a waiting period, for example 30 days.
- During that time, an owner who set a trap could reveal hidden proof of ownership, reclaim the coins, and take the collateral.
- Legitimate holders moving vulnerable bitcoin would also need matching collateral.
- The proposal would not protect coins whose owners no longer hold their keys.
- Fields described the ideas as thought experiments that depend on quantum-safe wallets and enforcement rules that have yet to be written.
How the example would work
Fields gave an example in which stealing 1 BTC would require the attacker to supply another 1 BTC from a quantum-safe wallet. Both coins would then be locked for a waiting period, such as 30 days.
Before quantum attacks become possible, the original owner could create a separate quantum-safe landmine containing hidden proof of ownership. If a thief later tried to drain vulnerable coins, the owner could reveal the proof during the waiting period and reclaim the bitcoin.
The thief would have no way to tell which holdings contained a trap before committing their own money. Fields said this could give owners an incentive to set traps in advance, and could make attackers wary of stealing coins that may be secretly guarded.
Limits for lost and inactive coins
Landmines only work for owners who still hold their keys. That rules out coins believed lost, including those associated with Satoshi Nakamoto.
Fields also sketched an auction idea for inactive coins. In that sketch, network rivals would stake hidden bids on a vulnerable wallet in advance. If a quantum thief attacked, the highest bidder's smart contract would trigger automatically, burn or destroy the thief's target coins, and transfer the thief's locked collateral to the winning bidder as a bounty.
The setup could add cost for honest holders. The blockchain cannot tell the difference between a quantum thief and the true owner. Someone moving their own 1 BTC under those rules would also need another 1 BTC as collateral. An early holder whose entire fortune sat in an old wallet would need matching funds to move it.
Ideas still at thought-experiment stage
Fields called the proposals "thought experiments." He assumed Bitcoin first gains quantum-safe wallets, and he left the rules needed to enforce the ideas unwritten.
The report also noted an earlier dispute over whether Bitcoin should freeze vulnerable coins or leave them available to whoever can produce a valid signature. A freeze could stop thieves, but it could also lock out owners who never upgraded.
Source for this report
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