# Bitcoin developer Cory Fields proposes collateral "landmines" that would make quantum thieves forfeit their own bitcoin

Anyone moving coins out of a quantum-vulnerable address would have to post matching collateral, and Blockstream separately reported a draft post-quantum Bitcoin Improvement Proposal and a restored Liquid peg in its third-quarter update.

- Published: 2026-11-06T09:52:06.667Z
- Canonical: https://polylog.news/crypto/2026-11-06/bitcoin-developer-cory-fields-proposes-collateral-landmines
- Publisher: Polylog (Crypto desk)
- Section: crypto
- Sources: [CoinDesk](https://www.coindesk.com/tech/2026/11/05/bitcoin-developer-proposes-landmines-to-make-quantum-thieves-lose-their-own-btc), [crypto.news](https://crypto.news/bitcoin-developer-quantum-landmines-btc-theft/), [Blockstream Blog](https://blog.blockstream.com/blockstream-quarterly-update-q3-2026/)

Cory Fields, a longtime Bitcoin developer, has proposed a deterrent against future quantum theft that does not freeze anyone's coins. Under his design, anyone trying to move bitcoin from an address exposed to quantum attack would first have to post matching collateral, [CoinDesk reported](https://www.coindesk.com/tech/2026/11/05/bitcoin-developer-proposes-landmines-to-make-quantum-thieves-lose-their-own-btc). Owners who prepared in advance would get a window to take both the coins and the attacker's stake. The proposal also sets [auction rules for coins whose owners are gone](https://crypto.news/bitcoin-developer-quantum-landmines-btc-theft/).

The idea addresses a split that has run through Bitcoin's quantum debate all year. BIP-361, a Bitcoin Improvement Proposal (BIP) co-authored by Jameson Lopp in April, would phase out old signature types and [effectively freeze coins left in vulnerable addresses](https://cointelegraph.com/news/bitcoin-devs-and-researchers-propose-freezing-quantum-vulnerable-coins-bip-361) five years after activation. Critics called that a break with Bitcoin's rule that valid signatures move coins. A BitMEX proposal would [freeze coins only after a quantum attack is proven](https://unchainedcrypto.com/bitcoin-developers-debate-quantum-canary-that-would-freeze-coins-only-after-an-attack-is-proven/). Fields's version leaves spending rules for owners unchanged and instead makes theft expensive. The open questions are whether an attacker with a working quantum computer would be deterred by collateral, and how a prepared owner would prove that preparation without exposing a key.

Blockstream's [third-quarter update](https://blog.blockstream.com/blockstream-quarterly-update-q3-2026/) says security was the company's main focus this quarter. It lists a draft post-quantum BIP for Bitcoin and a restored peg on Liquid, its federated sidechain. In its [second-quarter update](https://blog.blockstream.com/blockstream-quarterly-update-q2-2026/), Blockstream said its research team had moved post-quantum Bitcoin from a working deployment on Liquid to an opcode proposal. That route is opt-in: holders would move coins into new output types, and nothing would be confiscated.

## What this means

The mechanism at stake is the supply overhang from long-dormant coins in exposed addresses. Holders, miners and anyone pricing Bitcoin's monetary credibility are all exposed, because a freeze rewrites ownership rules and a theft would release coins onto the market. Developers want a defense that does not set a confiscation precedent, and they can deliver only what a broad soft-fork consensus will accept. That favors opt-in tools first. The consensus treats quantum risk as a single decision between freezing and doing nothing. The proposals now on the table show a third path: deterrence and voluntary migration. The likelier outcome is that over the next year an opt-in post-quantum output type, such as the opcode route Blockstream describes, advances before any freeze or collateral rule. Opt-in changes need no agreement about other people's coins. The read is wrong if a credible public demonstration of quantum hardware shortens the expected timeline and pushes developers toward a forced migration.

## What to watch

- Whether Fields's proposal reaches the Bitcoin development mailing list as a formal draft with a specification, because a draft would show whether the collateral mechanism can work without a hard fork.
- The text of Blockstream's draft post-quantum BIP, which will show which signature scheme and output type the Liquid deployment experience points toward.
- Whether institutional custodians start moving client coins out of addresses whose public keys are already exposed, an early sign that quantum risk has become a custody policy.