Bitcoin Core developer Cory Fields has proposed a mechanism called "quantum landmines" that would require anyone attempting to steal bitcoin with a quantum computer to first put their own funds at risk. Fields, who works at MIT's Digital Currency Initiative, posted the idea to the bitcoin-dev mailing list on Wednesday, November 4, 2026, labeling it a thought experiment.
How the proposal would work
Bitcoin relies on public-key cryptography, where a public key is visible to anyone and a private key proves ownership. Developers have long worried that a sufficiently powerful quantum computer could derive the private key from an exposed public key.
Fields' proposal uses a commit/reveal-style setup, similar to a sealed-bid auction. A participant first locks in a commitment without revealing details, then reveals them later, preventing others from copying or front-running the move.
The landmine itself would be a small output created in a quantum-safe format, designed to trigger rewards or penalties depending on how someone interacts with it. In practice, a would-be attacker would need to post collateral before making a move. Honest behavior returns the collateral; an attempted theft could result in forfeiture. The framework is also described as a way to protect auctions involving vulnerable coins.
Fields stressed that the soft-fork mechanics remain unresolved. A soft fork is a backward-compatible change to Bitcoin's rules, and implementing one would require broad community agreement. Fields said those details are pending further discussion.
Why timing matters
As of early November 2026, approximately 7.1 million BTC, roughly 35% of the circulating supply, sat in wallets with exposed public keys. Many of these are legacy addresses where the public key is already visible onchain. The count of exposed keys has risen significantly, helping push quantum risk from a fringe concern into a regular topic on developer channels.
Fields' post lands in an already crowded debate. Earlier proposals have focused on voluntary migration, where holders move funds into quantum-safe wallets on their own schedule. Others have explored soft-fork proposals aimed at managing at-risk UTXOs, the individual chunks of unspent bitcoin that make up every wallet balance.
Each approach carries a familiar tension. Voluntary migration respects property rights but depends on owners actually showing up, and some coins belong to people who may never return. Rule changes that restrict vulnerable coins could be more effective but raise uncomfortable questions about who gets to decide what happens to someone else's bitcoin. The landmine idea tries to sidestep part of that fight by changing the economics for the attacker instead of freezing or seizing anything.
What it means for Bitcoin and its holders
For now, this is a mailing list post, not a code change. No immediate responses appeared in the discussion thread, so the community has not yet weighed in on whether the mechanism holds up.
The proposal is notable for a few reasons. First, it reflects a shift in how developers are approaching the problem. Much of the quantum conversation has centered on cryptographic migration; Fields is adding an incentive layer, using game theory rather than math alone to raise the cost of an attack.
Second, it depends on infrastructure that does not exist yet. Quantum-safe wallets need to be standardized, built and adopted before any landmine could be planted, making Fields' idea a complement to migration work rather than a replacement.
Third, any version would need a soft fork, inheriting all the political friction that comes with changing Bitcoin's rules.
The roughly 7.1 million BTC with exposed public keys remains the figure to watch. Whether that number shrinks through voluntary migration, gets addressed through new rules, or becomes a test case for ideas like Fields' landmines will shape how the network handles a threat that has not arrived yet but is increasingly treated as a matter of when, not if.
The next step is the response on the bitcoin-dev list. If other developers start poking holes or proposing refinements, the thought experiment could begin turning into a specification.
