Cory Fields, a Bitcoin Core developer at MIT's Digital Currency Initiative, outlined a new quantum defense idea on the bitcoin-dev mailing list. The goal is to make anyone who cracks a wallet with a quantum computer risk their own coins first.

Under his example, moving 1 BTC from a quantum-vulnerable output would require another 1 BTC of collateral from a quantum-safe wallet, with both locked for a waiting period such as 30 days. Owners who prepared a hidden "landmine" with proof of ownership before Q-day could reveal it during that window, reclaim their coins and take the attacker's collateral.

An attacker cannot tell in advance which coins are guarded by a landmine, so every theft attempt risks losing the stake.

The scheme does not help coins believed lost, including Satoshi Nakamoto's, and honest holders moving vulnerable BTC would also need matching collateral. Fields called the ideas thought experiments that depend on quantum-safe wallets and enforcement rules that are not written yet.