From Decrypt · By Jose Antonio Lanz
In brief
Bitcoin developer Cory Fields proposed hidden “landmines” that could let wallet owners seize a quantum thief’s collateral.
Two auction designs would target apparently abandoned coins, where nobody may be around to spring a landmine.
Everything remains hypothetical: Bitcoin would need quantum-safe wallets, new consensus rules, and agreement on how to activate them.
Bitcoin developer Cory Fields has an unusual idea for dealing with future quantum thieves: Make them risk their own Bitcoin every time they try to steal someone else’s.
In a November 4 post to the Bitcoin development mailing list, Fields outlined “quantum landmines” and two types of auctions designed to turn attacks on vulnerable wallets into expensive gambles. He called the ideas “thought experiments,” not a completed Bitcoin upgrade.
Bitcoin owners use a secret private key to authorize transactions. A matching public key lets the network check their signatures without learning the secret.
If the whole idea seems too hard to understand, we used AI to generate a video to help you grasp it:
Today’s computers cannot realistically calculate that private key from the public one. A sufficiently powerful quantum computer could use a mathematical technique called Shor’s algorithm to do it, potentially letting a thief spend coins as if they owned them.
Some older Bitcoin outputs have exposed public keys, and certain newer formats reveal them too. Other addresses hide the key until someone spends, so the risk is not identical for every wallet.
Researchers call the hypothetical arrival of a computer capable of these attacks “Q-Day.” No publicly demonstrated machine can steal Bitcoin this way today, and nobody knows exactly when one might exist.
How does a quantum landmine work?
Imagine someone owns 1 BTC in an old, potentially vulnerable wallet. Before Q-Day, this person creates a tiny, separate quantum-safe Bitcoin output containing a hidden proof that they controlled the original private key while quantum theft was still impossible.
Think of it as a sealed ownership receipt. Outsiders can see the small output, but not the evidence tucked inside it, or even that it is a trap.
Now imagine a future thief uses a quantum computer to recover the user’s old private key. Under Fields’s suggested rules, the thief cannot simply take her 1 BTC: They must add 1 BTC of their own from a quantum-safe wallet as collateral.
PredictCryptoBTC Highs in November
80,00050%YesNo82,50037%YesNo85,00022%YesNo87,50013%YesNo90,0008%YesNo+6 more outcomes+5 more outcomesNEW$146.13 volumeCloses: Dec 1, 2026, 04:59 UTCCloses: Dec 1, 2026, 04:59 UTCBoth coins enter a restricted output worth 2 BTC. The thief must wait through a challenge period—30 days in Fields’s example—before spending it freely.