Adam Back, the cypherpunk cryptographer and Blockstream CEO whose work on Hashcash is cited in Satoshi Nakamoto’s original Bitcoin white paper, recently addressed growing concerns about quantum computing threats to Bitcoin’s security.
In a November 15, 2025, exchange on X formerly Twitter, Back downplayed the near-term risk, estimating that Bitcoin is unlikely to face a “cryptographically relevant” quantum attack for at least 20–40 years. This stance contrasts with more alarmist predictions, such as venture capitalist Chamath Palihapitiya’s claim that quantum computers could break.
Bitcoin’s SHA-256 hashing in as little as 2–5 years with around 8,000 qubits. Back’s comments were prompted by a user sharing Palihapitiya’s video, sparking a thread on Bitcoin’s vulnerability. No serious risk for 20–40 years or longer.
Current quantum computers are “too noisy and too small” to execute algorithms like Shor’s which targets elliptic curve cryptography in Bitcoin signatures or Grover’s which could speed up brute-force attacks on hashes like SHA-256. Today’s systems, such as Google’s Willow chip or Atom Computing’s 1,000+ qubit machines, fall far short of the millions of logical qubits needed for practical attacks.
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The Network can upgrade seamlessly via soft forks. Bitcoin uses signatures (e.g., ECDSA and Schnorr), not encryption, making it more resilient. Post-quantum (PQ) standards like NIST’s SLH-DSA standardized in 2024 are ready for integration.
Taproot activated in 2021 already enables “quantum-ready” commitments to alternate spending paths, allowing users to migrate without halting the network or paying premium fees for oversized PQ signatures today.
SHA-256 is “fairly robust” against quantum attacks. Grover’s algorithm could theoretically halve the search space from 2^256 to 2^128 possibilities, but that’s still computationally infeasible. Back noted that key sizes provide additional buffer.
Fears are often overhyped for marketing or during market dips. Back has consistently dismissed quantum FUD (fear, uncertainty, doubt) as exaggerated, calling it “quantum over-marketing.” In past posts, he’s joked about it being used to “load up on cheap Bitcoin” during price wobbles.
He advocates proactive “quantum readiness” (e.g., adding PQ options in the next 5 years) to calm markets without rushing unvetted tech. The discussion reignited amid Bitcoin’s price volatility and broader crypto debates on long-term security. While governments (e.g., US NIST) plan to deprecate ECDSA by 2030–2035 for federal systems.
Back argues Bitcoin’s decentralized, conservative development process—relying on peer-reviewed proposals (BIPs) and economic incentives—allows for measured upgrades without panic. He even speculated in an April 2025 interview that a real quantum threat might inadvertently reveal if Satoshi Nakamoto is alive, by forcing a move of their untouched ~1 million BTC to a PQ-secure address.
Critics like Palihapitiya highlight risks like “harvest now, decrypt later” storing encrypted data for future cracking, but Back counters that Bitcoin’s on-chain nature and upgradeability mitigate this.
Ongoing research, including hash-based signatures like SPHINCS+ basis for SLH-DSA, positions Bitcoin ahead of the curve.Back’s history of quantum skepticism dates back years; in 2020–2025 X posts, he repeatedly urged calm, emphasizing Bitcoin’s multi-decade lead time for defenses.
For now, Adam Back’s message: Focuses on fundamentals—quantum hype is noise, not signal. If you’re holding BTC, this reinforces the “HODL” ethos with a technical backstop.