Bitcoin Core developer Cory Fields has proposed a system called “quantum landmines” that could make future attackers risk losing their own Bitcoin when attempting to steal funds from wallets vulnerable to quantum computers.

  • Bitcoin Core developer Cory Fields has proposed “quantum landmines” to discourage future theft from vulnerable wallets.
  • The proposal would require anyone spending vulnerable Bitcoin to provide collateral equal to the coins’ value.
  • Original owners could recover stolen BTC and claim attackers’ collateral by revealing previously prepared ownership proofs.
  • Fields outlined auction mechanisms for vulnerable coins whose original owners may have permanently lost their keys.
  • The ideas remain hypothetical and would require quantum-safe Bitcoin outputs and new network consensus rules.

In a November 4 proposal published on the Bitcoin Development Mailing List, Fields outlined a mechanism requiring anyone moving vulnerable BTC to provide matching collateral from a quantum-safe wallet. The system would give original owners an opportunity to recover their coins and claim the attacker’s collateral if they had prepared proof of ownership beforehand.

Fields, who works with MIT’s Digital Currency Initiative, presented the concept as a possible response to future quantum computing threats. No such mechanism currently operates on Bitcoin.

Bitcoin quantum landmines would put attackers’ BTC at risk

The proposal addresses a security concern involving Bitcoin wallets whose public keys have already appeared on the blockchain. A sufficiently powerful quantum computer could theoretically use an exposed public key to calculate the corresponding private key.

Some of Bitcoin’s oldest transaction formats expose public keys directly, while address reuse can leave other holdings vulnerable. The concern includes dormant wallets associated with Bitcoin’s earliest years, although no publicly demonstrated quantum computer can currently carry out such an attack.

Fields proposed making anyone spending these vulnerable coins supply collateral equal to the amount being moved. Under his example, a person attempting to transfer 1 BTC would need another 1 BTC held in a quantum-safe wallet.

Both amounts would enter a new output with spending restrictions, including a possible 30-day waiting period. Someone who legitimately owned the original coins could prepare a hidden ownership commitment before quantum attacks became practical.

If an attacker later obtained the private key and attempted to move the Bitcoin, the owner could reveal that earlier commitment during the waiting period.

“However, Alice notices the transaction in the meantime,” Fields wrote, describing how the legitimate owner could reclaim her funds while taking the attacker’s collateral.

“However, Alice notices the transaction in the meantime,” Fields wrote, describing how the legitimate owner could reclaim her funds while taking the attacker’s collateral.

The attacker would not know beforehand whether the targeted wallet contained such a commitment. Fields suggested that the uncertainty could discourage attempts to steal coins, since a successful attack might ultimately cost the thief more than the targeted funds.

Bitcoin developer outlines auctions for lost wallets

The landmine mechanism depends on legitimate owners still controlling their private keys and preparing the necessary commitments before quantum attacks become possible.

Many older Bitcoin wallets may no longer meet those conditions. Some owners have lost their private keys, while others have left their holdings untouched for years.

To address that problem, Fields outlined a separate system allowing participants to place hidden bids against vulnerable holdings before an attack occurs.

In one example, a participant could prepare a bid against a dormant wallet containing 50 BTC. If a quantum attacker later attempted to spend those coins, an auction would begin after the initial ownership-proof period expired.

Participants could reveal their previously prepared bids and claim portions of the attacker’s collateral. Under the described mechanism, the vulnerable coins would be destroyed if an eligible bid prevented the attacker from keeping them.

Fields considered different rules for distributing collateral, including payments to successful bidders, miners or other designated recipients.

He discussed another auction design, suggested during conversations with MIT Digital Currency Initiative director Neha Narula, in which competing bidders could face financial penalties.

Neither auction system guarantees recovery for the original wallet owner. Their purpose would be to make theft less attractive by forcing attackers to risk their own funds.

Proposed Bitcoin protection could affect legitimate holders

The collateral requirement could create difficulties for people trying to move Bitcoin they legally own.

For example, someone holding 1 BTC in a vulnerable wallet would need another 1 BTC in a quantum-safe output to complete the transaction under Fields’ proposed rules.

A holder whose entire balance remained in an older wallet might therefore struggle to access those funds without obtaining additional Bitcoin.

Fields acknowledged that Bitcoin cannot automatically distinguish between a legitimate owner and an attacker who has recovered the same private key using quantum computing.

“The purpose of this post is just to introduce the ideas as thought experiments,” Fields wrote, noting that he had not specified the software changes needed to implement them.

Any implementation would first require quantum-safe transaction outputs and new consensus rules governing vulnerable coins.

Bitcoin developers have been considering other possible protections. As crypto.news previously reported, Coinbase urged developers in October to prepare for quantum threats, warning that migrating existing wallets could take several years.

Research published by Fireblocks similarly identified exposed public keys as a major concern, with estimates placing millions of BTC in potentially vulnerable addresses.

A separate BitMEX quantum proposal suggested activating restrictions on older wallets only after evidence of a successful quantum attack.

Fields’ mailing-list discussion leaves several design choices unresolved, including collateral ratios, auction deadlines, penalties for losing bids and the conditions under which vulnerable coins could be destroyed.