A smaller projected machine
An Alice & Bob-led preprint estimates that solving the elliptic curve problem used by Bitcoin’s secp256k1 signature system could require at most about 30,000 cat qubits and roughly one hour, under the paper’s fault tolerance assumptions. The same study estimates that factoring an RSA-2048 key would require 22,593 cat qubits and 3.14 days.
The company’s cat qubit architecture is designed to reduce certain error correction demands by using quantum states that are less vulnerable to bit flip errors. In a company announcement, Alice & Bob CEO Théau Peronnin described the estimate as a step toward improving the balance between the size and speed of a fault tolerant quantum computer. The post also connects the research to Bitcoin, which relies on a related elliptic curve cryptographic system.
The estimate is substantially below a separate projection discussed by CoinDesk, which reported on the study. Google had estimated in March that fewer than 500,000 physical qubits could eventually be sufficient, although the two analyses use different machine designs and assumptions. On the figures alone, Alice & Bob’s estimate is about 17 times smaller.
The practical concern is concentrated in addresses whose public keys have already been exposed. Once a public key is visible, a sufficiently capable quantum computer could theoretically use Shor’s algorithm to calculate the corresponding private key. That could allow an attacker to authorize a transfer without needing to defeat Bitcoin’s underlying blockchain consensus rules.
CoinDesk reported that more than 6 million BTC are held behind public keys that are already exposed. Those coins could give an attacker more opportunity than a conventional transaction race. The modeled attack would take about 62 minutes, while Bitcoin typically adds a block roughly every 10 minutes. That timing would make it difficult to replace an ordinary transaction before confirmation, but coins sitting at exposed addresses would not necessarily be tied to a pending transaction.
The hardware gap remains decisive
The announcement’s headline estimate has drawn criticism because the modeled machine is far removed from demonstrated quantum hardware. Security analyst Marin Ivezic argued that the calculation assumes bit flip times on the scale of a century, while important engineering questions about gate operations and multi-qubit control remain unresolved. In that view, reducing the number of required qubits on paper does not establish that a workable machine is close.
That criticism goes to the central disagreement. Alice & Bob’s result may lower the theoretical resource requirement, but it does not show that a 30,000-qubit computer can be built, operated reliably or connected to the supporting systems needed for a sustained cryptographic attack. The gap between a resource estimate and a deployable machine is therefore still a major barrier.
A separate technical reaction emphasized the same limitation. CryptoPotato reporter Jose Oramas noted that the estimate assumes no bit flips during the computation and that Alice & Bob’s largest reported demonstrator has only 12 qubits. The comparison illustrates the difference between the scale of the proposed system and the company’s existing hardware demonstrations.
A governance problem before an attack
Alice & Bob cryptanalyst Dahmun Goudarzi supports beginning migration to quantum resistant security now, according to CoinDesk. Goudarzi also acknowledged that the estimate is theoretical and that the team has not established whether adding more qubits could reduce the attack time below Bitcoin’s confirmation interval.
That uncertainty creates a policy and coordination problem. Replacing Bitcoin’s signature system would require agreement among developers, wallet providers, exchanges, miners and holders. It would also require users to move funds from vulnerable address types without creating new operational or custody risks.
The immediate conclusion is not that Bitcoin has been cracked. No existing quantum computer can perform the proposed attack. The significance of the research is that the projected hardware barrier may be moving into a range that developers can no longer treat as a remote engineering question. Planning a transition could take years, while waiting for a practical machine to appear could leave less time to protect exposed assets.
Sarah Thompson is not a person. No notebook, no deadlines, no face behind the name — just a byline this newsroom publishes under. Here is the production line underneath it, because a name beside a portrait reads like a journalist, and this one is not one.
The models. Writing: gpt-5.6-luna. Out on the live web: gpt-5.6-luna and gpt-5.6-terra. Pictures: gpt-image-1. Swap one in the newsroom and this line swaps with it — it is read off the machines, not typed here.
How a story is made
- Research. The searching model reads around the story, pointed at primary sources — the filing, the post, the repository — rather than at somebody else's write-up of them.
- Writing. The writing model drafts it against what was found, at Sarah Thompson's usual length and in Sarah Thompson's usual register.
- The loop. A reviewer reads the draft and sends it back with notes. Then reads it again. A piece can go round several times before it leaves the building.
- Enrichment. A quotation has to appear word for word on the page it is taken from. A chart may only use figures that appear in the source it cites. Whatever fails is dropped, and the reason is kept.
- Fact check. A last pass hunts for claims the article makes and its sources do not.
- A human stop. Sensitive subjects are held for a person to read before publication, and a person can kill any of it at any point.
If that sounds less like a newsroom and more like a factory: quite. It is called Press Factory.
This article was generated using AI and published automatically without human pre-publication review.
Read and checked by admin on 10/30/2026
How this article was made
The article was produced by the Grandmonts Media News Engine using automated research, drafting and verification workflows. No human editor reviewed the article before publication. Grandmonts Media remains responsible for the published content. Errors can be reported at office@grandmonts.cz.