Bitcoin’s Quantum Defense Could Make Thieves Pay Their Own Ransom

Bitcoin Core developer Cory Fields proposed “quantum landmines” on November 4 to the Bitcoin Development Mailing List, outlining a way for owners of potentially vulnerable Bitcoin to recover stolen funds while forcing quantum attackers to post their own $BTC as collateral. Fields described the proposals as “thought experiments,” not a completed Bitcoin upgrade.

Under the proposal, an owner of 1 BTC in an older wallet could create a separate quantum-safe output containing secret evidence that they controlled the original private key before Q-Day. If a quantum thief later recovered that key and attempted to spend the 1 BTC, the attacker would need to add 1 BTC of quantum-safe collateral. Both amounts would enter a restricted output worth 2 BTC and remain locked for a 30-day challenge period. The owner could then reveal the pre-Q-Day proof and recover the original 1 BTC plus the attacker’s collateral, meaning a successful key theft could still produce a 1 BTC loss for the thief.

Fields argued that attackers would become “wary of stealing coins as they may be secretly guarded by mines.” The mechanism would require normal post-Q-Day transfers of vulnerable coins to include matching collateral, however. An owner holding 10 BTC in an older wallet could need another 10 BTC in quantum-safe funds to move it, creating a substantial obstacle for legitimate holders without sufficient additional holdings.

The proposal would not protect dormant Bitcoin whose private keys have already been lost, including some Satoshi-era holdings widely believed to be inaccessible. In a June 20, 2026 post shared by BeInCrypto, Binance founder CZ proposed freezing Satoshi’s stack and said, “Why don't we give a timeline say within 6 months or 12 months, if those coins don't move then we're going to lock them.” Fields also proposed auction mechanisms through which bidders could challenge an attacker and claim the deposited funds; one version would permanently destroy the vulnerable coins.

No publicly demonstrated machine can currently steal Bitcoin using Shor’s algorithm, and the hypothetical arrival of a computer capable of doing so—known as Q-Day—has no established date. The risk also varies by address type: some older Bitcoin outputs expose their public keys, certain newer formats reveal them, and other addresses conceal the key until the coins are spent.