Bitcoin Safe from Quantum Threat for 20–40 Years, Says Cryptographer Adam Back

Bitcoin is unlikely to face a meaningful threat from quantum computing for at least two to four decades, according to cypherpunk and Blockstream CEO Adam Back.

The longtime cryptographer, who was cited in the original Bitcoin white paper, said current fears circulating on social media over an imminent “quantum attack” are overstated.

Back made the comment on Nov. 15 while responding to an X user who asked whether Bitcoin was at risk as quantum research accelerates.

He wrote that Bitcoin is “probably not” vulnerable for “20–40 years,” pointing out that the National Institute of Standards and Technology has already approved post-quantum encryption standards that Bitcoin could adopt long before quantum computers reach a level where breaking SHA-256 becomes realistic.

Despite Viral Predictions, Practical Quantum Attacks Remain Far From Reality

His response followed a viral video of venture capitalist Chamath Palihapitiya, who predicted that the quantum threat could emerge in as little as two to five years.

Palihapitiya argued that roughly 8,000 qubits would be required to break SHA-256. Back pushed back on the timeline, explaining that today’s machines are far too noisy and far too small.

The highest-capacity neutral-atom system, built at Caltech, has reached about 6,100 physical qubits. However, this remains unusable for breaking cryptography because real-world qubits require heavy error correction.

Systems with more stable qubits, such as Quantinuum’s Helios, still only deliver about 48 logical qubits.

Gate-based systems recently passed 1,000 qubits with Atom Computing, but this is far from the thousands of logical qubits needed to run Shor’s algorithm on current standards like RSA-2048 or Bitcoin’s elliptic curve signatures.

While experts agree that practical quantum attacks are not achievable today, the long-term threat remains.

The idea of “harvest now, decrypt later,” where attackers collect encrypted data now and decrypt it in the future, has already become a concern in traditional cybersecurity.

This technique does not directly affect Bitcoin’s ownership model but highlights the need for timely upgrades across the digital world as quantum capabilities evolve.

Is Bitcoin Really Ready for the Quantum Era?

The debate over preparation has intensified across the Bitcoin community this year.

In November, on-chain analyst Willy Woo urged users to move coins from Taproot addresses, arguing that addresses exposing public keys directly could become vulnerable first.

Former Bitcoin Core developer Jonas Schnelli said older formats offer more short-term protection, though he warned that no user-initiated migration plan can be considered fully safe once quantum machines reach the mempool-level attack threshold.

Developers are now examining Bitcoin Improvement Proposal 360, which introduces quantum-resistant ML-DSA signatures selected by NIST in 2024.

The plan, drafted by Jameson Lopp, outlines a multi-year transition to phase out older signature schemes before quantum machines become relevant.

Supporters argue it provides structure to a complex upgrade process, while others say only a protocol-level overhaul will give users reliable protection.

Industry voices remain split on timelines. Some, including Solana co-founder Anatoly Yakovenko, warn that a breakthrough within five years cannot be ruled out as AI accelerates research.

Analysts estimate that roughly 6 to 7 million BTC sit in older address formats that would be first in line for a quantum attack.

El Salvador, which holds more than 6,000 BTC in its national reserve, recently redistributed its treasury across 14 addresses to reduce exposure after criticism over single-address storage.

Multiple quantum researchers have revised their projections closer to the late 2020s or early 2030s, noting that required machine sizes have consistently dropped as hardware improves.

Some startups now claim that specialized designs with hundreds of thousands of qubits could threaten 256-bit elliptic curve signatures.

At the same time, engineers recognize that upgrading decentralized networks requires far more coordination than updating traditional systems.

Post-quantum signature schemes often involve larger keys and higher computational loads, posing challenges for wallet developers and miners.

Projects such as Rootstock and Naoris Protocol have begun experimenting with post-quantum infrastructure, and hardware wallets like Trezor’s Safe 7 now ship with quantum-secure update paths.

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