Cory Fields proposes quantum landmines to deter Bitcoin theft

The Bitcoin Core developer wants future quantum attackers to put their own coins at risk before they can touch anyone else's

Thu 5 Nov 2026 · 20:35 EST · 4 min read

In Bitcoin

Bitcoin’s quantum problem has mostly been framed as a race: upgrade the network before someone builds a machine capable of cracking its cryptography. Cory Fields wants to add a second idea to the mix: make the thief pay first.

Fields, a Bitcoin Core developer who works at MIT’s Digital Currency Initiative, posted a proposal to the bitcoin-dev mailing list on Wednesday, November 4, 2026. He calls the concept “quantum landmines.” The goal is simple to state and hard to build. Anyone trying to steal coins with a quantum computer would first have to risk their own money.

He was careful to label it a thought experiment. The design leans on quantum-safe wallets and enforcement rules that nobody has written yet.

How a quantum landmine would work

Start with the threat. Bitcoin relies on public-key cryptography, where a public key can be seen by anyone and a private key proves ownership. Developers have long worried that a sufficiently powerful quantum computer could work backward from an exposed public key to the private key behind it.

That is the scenario Fields is trying to discourage. His proposal uses a commit/reveal-style setup, which works a bit like a sealed-bid auction. A participant first locks in a commitment without showing their hand, then reveals the details later. Because the commitment comes first, nobody can see someone else’s move and simply copy or front-run it.

The “landmine” itself would be a small output created in a quantum-safe format. That output is designed to trigger either rewards or penalties depending on how someone interacts with it. The practical effect is that a would-be attacker must post collateral before making a move.

Put more plainly, a quantum thief would need skin in the game. Behave honestly and the collateral comes back. Get caught attempting theft and it could be forfeited.

The framework is also described as a way to protect auctions involving vulnerable coins. Fields stressed that the soft-fork mechanics are still unresolved. A soft fork is a backward-compatible change to Bitcoin’s rules, the kind of upgrade the network has used before to add features without splitting the chain. Getting there requires broad community agreement, and Fields said those details are pending further discussion.

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Why the timing matters

The numbers explain why developers keep returning to this topic. As of early November 2026, approximately 7.1 million BTC, roughly 35% of the circulating supply, sat in wallets with exposed public keys.

That is a large share of the network’s value sitting in exactly the kind of addresses a quantum attacker would target first. Many of these are legacy addresses, older formats where the public key is already visible onchain. The count of exposed keys has risen significantly, which has helped 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 specifically 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 they 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. Instead of freezing or seizing anything, it changes the economics for the attacker.

What this 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.

Still, the proposal is worth watching 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. That makes Fields’ idea a complement to migration work, not a replacement for it.

Third, any version of this would need a soft fork, which means it inherits 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 keep an eye on. 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.

Disclosure: This article was edited by Vivian Nguyen. For more information on how we create and review content, see our Editorial Policy.