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

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. 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.

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 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. 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 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, 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.