Adam Back says Bitcoin faces no meaningful quantum threat for at least the next 20–40 years, adding that NIST-approved post-quantum standards can be adopted in time.
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Adam Back, the cryptographer and cypherpunk cited in the Bitcoin white paper, said Bitcoin is unlikely to face a meaningful threat from quantum computing for at least two to four decades.
to an X user on Nov. 15 who asked whether Bitcoin () is at risk, Back wrote that “probably not for 20–40 years,” adding that there are already approved by the National Institute of Standards and Technology (NIST) that Bitcoin could implement “long before cryptographically relevant quantum computers arrive.”
The discussion began with a user posting a video of Canadian-American venture capitalist and entrepreneur Chamath Palihapitiya, who predicted that the quantum threat to Bitcoin would become a reality in two to five years. He noted that to break SHA-256 — the encryption standard that Bitcoin relies on — quantum computers would need about 8,000 qubits.
During a mid-April interview with Cointelegraph, the suggested that quantum computing pressure may reveal . Back explained that quantum computing could make the Bitcoin held by Satoshi Nakamoto vulnerable to being stolen, forcing him to move it to a new address to avoid losing access to his coins.
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The current state of quantum computing
Current quantum computers are either significantly too noisy to support encryption-breaking or severely lack in qubit count. For instance, the Caltech neutral-atom array — the current qubit count record-holder — has as many as but is incapable of breaking RSA-2048, even though it is estimated to need only about 4,000 logical qubits.
The reason is that the 4,000-qubit rough estimate is an idealized model that assumes perfect local qubits — not accounting for real-world noise. Put simply, 4,000 qubits is the number required to run the encryption-breaking Beauregard’s Shor circuit on RSA-2048 in an error-free environment — this kind of qubit is called a logical qubit.
Less error-prone trapped-ion systems, such as Quantinuum’s , reached 98 physical qubits, acting as 48 error-corrected logical qubits — meaning we get one usable qubit for every two physical qubits. Universal gate-based quantum computers 1,180 qubits with Atom Computing — the first such system to cross 1,000 qubits back in late 2023.
Current quantum computers are far from being able to threaten current cryptographic standards. Still, experts debate how long it will take to close the gap. Some expect linear progress, while others expect a breakthrough as the research field continues to attract significant investment.
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The quantum threat we face today
While it is unlikely that quantum computers will break modern encryption anytime soon, their likely future existence poses a threat today. “Harvest now, decrypt later” is a type of attack in which attackers collect data and store it until future technology enables decryption.
This type of issue does not affect Bitcoin, which utilizes encryption to ensure that only the rightful owners can access their assets. As long as Bitcoin implements quantum-resistant systems in a timely manner, it will remain safe.
Still, this kind of attack affects anyone who uses encryption to ensure that information remains safe from prying eyes in the long run. If a dissident in a totalitarian country is protected by encryption, the user would like to ensure that the data will remain protected for 10, 15, 20, or more years into the future.
Gianluca Di Bella, a smart-contract researcher specializing in zero-knowledge proofs, recently ” to post-quantum encryption standards for this very reason. He said that might be 10 or 15 years away, but cautioned that “big institutions like Microsoft or Google might have a solution in a few years.”
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