A new proposal on the Bitcoin Development Mailing List explores how the network might respond if quantum computers one day become powerful enough to break older Bitcoin wallet cryptography. Bitcoin Core developer Cory Fields outlined a mechanism he calls “quantum landmines,” aimed at making theft from vulnerable addresses expensive and risky rather than easy and profitable.
Fields presented the idea on November 4 as a possible defense for coins held in older wallets that could be exposed after a so-called Q-Day. The concept would let owners prepare a hidden proof of ownership in advance, then use that proof to reclaim funds and capture a thief’s collateral if someone tries to move the coins after quantum attacks become practical.
How the proposed trap would work
Under the concept described by Fields, a holder of vulnerable Bitcoin would create a secret proof of ownership before Q-Day and embed it in a small quantum-safe output. That proof would remain hidden unless it needed to be used later.
If a quantum attacker then tried to move, for example, 1 BTC from that exposed wallet, the spender would also have to post 1 BTC as matching collateral. Both the original coins and the deposit would be locked during a waiting period that Fields suggested could be around 30 days.
During that window, the original owner could reveal the hidden proof, recover the stolen bitcoin, and take the attacker’s collateral as well. In effect, the thief would risk losing money by attempting the theft.
Deterrence through uncertainty
The proposal is designed around doubt rather than perfect prevention. Because an attacker would not know which old wallets had been prepared with these hidden traps, Fields argued that they could become reluctant to target any vulnerable coins at all.
The central premise is that stealing old Bitcoin should no longer be a one-way gain. If enough addresses were potentially protected, a quantum hacker would face the possibility that a successful-looking theft could later turn into a loss.
Why legitimate users would also be affected
The biggest complication is that the blockchain cannot tell the difference between a hacker using a broken key and a legitimate owner moving their own funds. As a result, the same collateral rule would apply to everyone spending from wallets considered vulnerable to quantum attacks.
That makes the proposal costly for honest users as well. A person with 10 BTC in an older exposed wallet might need an additional 10 BTC in quantum-safe funds just to move those coins. The burden could make recovery difficult for holders who have assets but not enough separate safe collateral.
The problem of lost coins and dormant wallets
Fields also addressed a harder class of cases: old Bitcoin whose private keys are gone, including long-dormant holdings from Bitcoin’s earliest years. If no owner can prepare a landmine in advance, those coins could remain open to quantum theft under the basic version of the idea.
To deal with that, he suggested alternative auction-style mechanisms in which outside bidders could challenge a hacker and potentially claim the posted deposit. One version discussed in the article would permanently destroy the vulnerable coins instead. That approach would raise broader questions about ownership and Bitcoin’s total supply.
Debate likely to center on trade-offs
The proposal does not resolve the larger quantum threat by itself, but it frames one possible response: discourage theft by forcing anyone who moves vulnerable coins to put equal value at risk. The same structure that could punish attackers, however, would also make it more expensive for legitimate holders to access older funds.
For now, the confirmed next step is discussion. Fields has placed the idea before the Bitcoin development community, where debate is likely to focus on whether the deterrent value would justify the added cost and complexity for owners of older wallets.
Source: beincrypto.com