Bitcoin's New Quantum Defense Could Penalize Attackers With BTC Collateral

A Bitcoin Core developer has introduced a proposal that could make attempts to steal Bitcoin using quantum computing financially costly for attackers. The concept, known as “quantum landmines”, would require anyone attempting to spend vulnerable coins to put up their own Bitcoin as collateral, creating a potential financial penalty for unauthorized access.

Cory Fields, a Bitcoin developer working with the Massachusetts Institute of Technology’s Digital Currency Initiative, presented the idea on Wednesday in a discussion on the Bitcoin development mailing list. His proposal explores how Bitcoin holders could establish cryptographic safeguards in advance, allowing them to challenge future attempts to access their wallets if quantum computing eventually makes current cryptographic protections vulnerable.

The concept addresses growing concerns that sufficiently advanced quantum computers could undermine Bitcoin's existing security model. Such machines could potentially derive a wallet's private spending key from its publicly exposed key, allowing attackers to authorize transactions and transfer its funds without the owner's consent.

This risk is particularly relevant to older Bitcoin holdings. Some early transactions exposed public keys directly, potentially leaving coins associated with Bitcoin's pseudonymous creator, Satoshi Nakamoto, and other early participants vulnerable to future attacks.

The proposal also introduces another dimension to an ongoing debate within the Bitcoin community: whether vulnerable coins should eventually be frozen to prevent quantum-enabled theft or remain accessible to anyone capable of producing a valid cryptographic signature. Freezing these holdings could protect them from attackers, but it could also permanently prevent legitimate owners from accessing their funds if they have not migrated to quantum-resistant wallets.

How Bitcoin's Proposed Quantum Landmines Would Work

Fields' approach seeks to discourage unauthorized transactions by making attackers risk losing additional Bitcoin when attempting to access vulnerable holdings.

Under the proposed mechanism, an owner could prepare a separate quantum-resistant wallet containing cryptographic evidence that establishes their right to the original funds. This evidence would remain concealed until someone attempts to spend the vulnerable coins.

If an attacker successfully uses quantum computing to access a wallet and initiates a transaction, the system would require them to commit an equivalent amount of Bitcoin from a quantum-resistant wallet as collateral.

For example, an attempt to steal 1 BTC would require the attacker to put another 1 BTC at risk. Both amounts would then enter a temporary holding period, potentially lasting 30 days, during which neither party could immediately spend the funds.

This delay would give the legitimate owner an opportunity to identify the suspicious transaction and demonstrate prior ownership by revealing the cryptographic proof stored in their landmine.

Once the proof is submitted, the original owner could redirect their Bitcoin to a previously designated secure address while also claiming the attacker's locked collateral as a penalty.

An important feature of the proposal is that attackers would not be able to determine in advance whether a particular wallet contains one of these safeguards. Consequently, they would have to commit their own funds without knowing whether the attempted theft would ultimately generate a profit or result in a financial loss.

Why Quantum Attackers Could Lose Their Own Bitcoin

The effectiveness of Fields' proposal depends on introducing uncertainty into the attacker's decision-making process.

Before quantum computers become capable of compromising Bitcoin wallets, holders could establish these hidden safeguards without revealing their existence publicly. An attacker discovering a vulnerable wallet would therefore have no reliable way to know whether its owner had already prepared a quantum landmine.

Fields illustrated the mechanism through a hypothetical scenario involving Alice, a Bitcoin holder who secures her funds before quantum attacks become practical.

If an attacker later attempts to spend Alice's vulnerable Bitcoin, they would have to wait through the designated lock-up period before gaining unrestricted control of the funds. During that interval, Alice could detect the transaction, reveal her previously committed ownership proof and reclaim her Bitcoin.

By doing so, she would also become entitled to the attacker's collateral under the proposed mechanism.

Fields explained that the attacker would lack any pre-quantum proof demonstrating knowledge of Alice's private key. As a result, the attacker would have to wait for the 30-day period to expire before attempting to spend the locked output again. Alice, meanwhile, could use the waiting period to reveal her proof, recover her funds and collect the collateral.

This arrangement would effectively turn the potential theft into a financial risk for the attacker rather than allowing them to profit automatically from compromising an exposed key.

Bitcoin's Lost Coins May Require a Different Quantum Protection Mechanism

Despite its potential, the landmine approach has a significant limitation: it depends on the original owner remaining active and retaining access to the necessary cryptographic keys.

This means it cannot directly protect Bitcoin holdings whose owners have lost their keys or are no longer available to respond to suspicious transactions. Satoshi Nakamoto's long-dormant Bitcoin holdings are among the examples frequently discussed in connection with this problem.

To address these inactive wallets, Fields outlined a second concept based on an auction mechanism that would allow other network participants to commit funds in advance to protect vulnerable Bitcoin holdings.

Under this arrangement, participants would submit concealed bids associated with wallets considered exposed to future quantum attacks. These commitments would function as another form of cryptographic safeguard, with the highest bidder gaining the right to execute a predetermined response if someone attempts to spend the targeted coins.

If a quantum-enabled attacker initiates a transaction against a protected wallet, the winning bidder's pre-established mechanism would activate automatically. The proposed response would destroy or burn the targeted Bitcoin, preventing the attacker from obtaining it.

At the same time, the attacker's locked collateral would be seized and transferred to the winning bidder as a bounty.

Unlike the first proposal, this mechanism would not depend on the original owner being available to demonstrate ownership or recover the funds. Instead, it would rely on advance commitments from other participants willing to financially back the protection of vulnerable holdings.

However, the auction model introduces its own questions about incentives, implementation and the potential consequences of allowing third parties to determine the fate of dormant Bitcoin.

Quantum Landmines Could Also Increase Costs for Legitimate Bitcoin Owners

Although the proposed mechanisms are designed to discourage theft, they could impose additional financial requirements on ordinary Bitcoin holders.

The underlying challenge is that the blockchain cannot independently distinguish between a legitimate owner attempting to move their own funds and an attacker using quantum computing to access someone else's wallet.

Consequently, the collateral requirement could apply to both parties.

For instance, a legitimate holder attempting to transfer 1 BTC under the proposed rules would also need to provide another 1 BTC as collateral. This could create a substantial obstacle for early Bitcoin investors whose holdings are concentrated in older wallets and who may not have additional funds available to meet the requirement.

The problem could be particularly significant for long-term holders who have retained their Bitcoin for years without maintaining additional liquid reserves. Even if they are the rightful owners, moving their funds could become more expensive under a system designed to prevent unauthorized transactions.

These trade-offs highlight the difficulty of introducing quantum-resistant protections without creating new barriers for existing Bitcoin holders.

Bitcoin's Quantum Protection Proposals Remain Experimental

Fields described the quantum landmine and auction concepts as thought experiments rather than finalized technical proposals. Both approaches assume that Bitcoin will first develop and adopt quantum-resistant wallets capable of supporting the necessary cryptographic commitments.

He has not yet provided a complete set of implementation rules explaining how the proposed mechanisms would operate at the protocol level or how the network would enforce the associated collateral requirements.

Nevertheless, the ideas offer a different perspective on Bitcoin's potential response to quantum computing. Instead of relying exclusively on upgrading cryptographic signatures or freezing vulnerable holdings, they explore whether economic incentives and financial penalties could help discourage future attacks.

Can Bitcoin Balance Quantum Security With Ownership Rights?

Fields' proposals highlight a central challenge facing Bitcoin as quantum computing advances: protecting vulnerable holdings without undermining the ownership rights of legitimate investors. While quantum landmines could introduce a financial deterrent against unauthorized spending, their effectiveness would depend on advance preparation, access to additional collateral and the adoption of quantum-resistant infrastructure.

The distinction between active and dormant wallets also makes a universal solution difficult. Owners who retain their keys may be able to establish protective mechanisms themselves, whereas lost or abandoned holdings would require alternative arrangements that could involve third-party incentives and decisions about whether those coins should remain accessible.

More broadly, the proposals suggest that Bitcoin's transition to quantum-resistant security may involve more than replacing its existing cryptographic tools. It could also require reconsidering how ownership is demonstrated, how suspicious transactions are challenged and who has the authority to intervene when a wallet becomes vulnerable. The challenge will be finding a mechanism that discourages quantum-enabled theft without forcing legitimate holders to surrender access to their assets or bear disproportionate costs to prove ownership.