Originally reported by ChainCatcher on November 12, 2026, at 09:18 (UTC+8). This is a look back at the report’s claims, not a new development.
A Bitcoin Security Consortium report, produced with Presidio Bitcoin, argues that quantum computing poses a serious potential risk to Bitcoin’s signatures. Its sharpest scenario is an attacker deriving a private key while a transaction waits to enter a block. But the report is equally clear on the missing piece: no cryptographically relevant quantum computer has been demonstrated.
What is exposed—and when?
The report describes two distinct risks. In a static attack, a quantum computer would target coins whose public keys are already exposed, including coins at reused addresses and older pay-to-public-key (P2PK) outputs. Citing Project Eleven, it estimates that about 7.1 million BTC, or roughly 35% of the total, would be vulnerable if a capable machine existed today. It says around three-quarters of that amount sits at reused addresses, much of it at large exchanges.
An in-transit attack would target a public key revealed when a transaction is broadcast, before that transaction enters a block. The report cites a Google estimate that a suitably fast, prepared quantum device could derive one private key in as little as nine minutes. That is a theoretical calculation, not a demonstrated Bitcoin theft or a fixed window for every transaction.
What has changed—and what has not?
The report points to progress in quantum error correction and proposed optimizations of Shor’s algorithm, including Google’s Willow work and research published in 2026. It distinguishes those results and circuit designs from a machine capable of attacking Bitcoin. By its account, Quantinuum had demonstrated 48 error-corrected logical qubits, while breaking Bitcoin’s elliptic-curve cryptography would require at least roughly 1,200.
The near-term step identified in the report is moving funds away from reused addresses; that does not require a Bitcoin rule change. A post-quantum signature scheme is a different matter. The report says Blockstream tested its proposed SHRINCS scheme on Liquid in March 2026 and published a Bitcoin improvement proposal with other contributors in August. A formal security proof remained outstanding, and Bitcoin-wide deployment would require a soft fork. A proposal and a Liquid test are not an enacted Bitcoin upgrade.
The hardest dispute concerns older P2PK coins that may no longer have accessible owners. In one section, the report puts P2PK exposure at about 1.8 million BTC; in its discussion of possible rules, it cites roughly 1.7 million BTC across about 20,000 addresses, including an estimated 1.1 million attributed to Satoshi Nakamoto. Presidio Bitcoin describes options under discussion ranging from leaving old spending valid to slowing it or freezing it with a recovery path. None is presented as settled policy.
The distinction matters more than the dramatic clock: the report makes a case for preparing for a possible attack, not for claiming that a nine-minute quantum attack exists today.