The main quantum threat to Bitcoin is not block production. It is ownership. The report says around 6.9 million BTC, roughly one-third of all bitcoin ever mined, sits in wallets whose public keys are already permanently visible onchain. That pool includes about 1 million BTC attributed to Satoshi Nakamoto, placing a large share of early coins in the exposed category.
Bitcoin mining relies on hashing, and the article says quantum computers cannot meaningfully break that part of the system. The ledger would remain intact. New bitcoin would still only be created through mining, and blocks would keep coming. The weak point is wallet security, which depends on one-way mathematics: deriving a public key from a private key is easy, but reversing that process is supposed to be infeasible for a conventional computer.
Exposed public keys create a large target set
According to the piece, the vulnerable pool is concentrated in addresses where the public key is already known. Much of that comes from Bitcoin’s early years, when one address format revealed the public key by default. Another source is any wallet that has ever been spent from, because spending discloses the key tied to whatever balance remains at that address.
That changes the attack model. A quantum attacker would not need to race a live transaction moving across the network. The report says they could go through already exposed wallets at their own pace, one after another. Satoshi’s coins, untouched since the early days of the network, are listed in that same group.
Taproot improved transaction design but widened the exposure issue
The article points to the 2021 Taproot upgrade as another factor that expanded the problem. Taproot changed how Bitcoin addresses work, aiming to make transactions more efficient and private. Its side effect, as described in the report, is that any bitcoin spent since Taproot activation has revealed the key protecting the remaining funds at that address.
The piece does not frame this as a design error. It describes the outcome as a reasonable tradeoff made at a time when quantum timelines appeared much longer. That assumption now looks less comfortable.
Google paper lowered estimated resources for a possible attack
The report says Shor’s algorithm collapses the gap between public-key exposure and private-key recovery. It also highlights a Google paper published this month, saying the attack may require far fewer resources than previously estimated. In the article’s framing, the timing window now runs against Bitcoin’s own block intervals.
That leaves Bitcoin facing a coordination problem as much as a technical one: whether a network built to resist centralized change can organize what the article describes as the biggest security upgrade in its history before hardware capabilities catch up.
Bitcoin has no concrete rollout yet, while Ethereum has a formal program
On the response side, the article says recent months have brought intense debate, and other blockchains are already preparing. Still, nothing concrete has emerged from Bitcoin developers so far. Ethereum, by contrast, has maintained a formal quantum-resistant program since 2018.
The Ethereum Foundation is said to have four teams working full time on the migration, along with more than ten independent developer groups releasing weekly test networks. Its roadmap spreads the upgrades across four upcoming network-wide changes, and progress is published through the dedicated site pq.ethereum.org.