Bitcoin Faces Renewed Scrutiny Over Quantum‑Computing Threat
June 2026 – A growing chorus of investors, exchanges and researchers is revisiting the possibility that advances in quantum computing could weaken the cryptographic foundations of Bitcoin. While many still view the danger as a medium‑ to long‑term concern, recent actions by major market participants suggest the issue is moving up on the industry’s risk‑management agenda.
A shift in market sentiment
In mid‑January, Christopher Wood, global head of equity strategy at Jefferies, abruptly removed the entire Bitcoin position from his “Greed & Fear” model portfolio—a move that erased roughly a 10 % allocation that had been part of the fund’s benchmark for years. In a Bloomberg interview Wood cited “emerging quantum‑computing capabilities” as a catalyst for his decision, warning that the technology could eventually erode the security model that underpins Bitcoin’s consensus.
Just days later, Coinbase announced the creation of an independent advisory board composed of both cryptocurrency and quantum‑science experts. The group’s mandate is to evaluate the exposure of blockchain protocols to quantum attacks and to outline migration pathways toward post‑quantum‑secure digital signatures.
Both steps reflect a noticeable departure from the earlier stance that quantum threats were largely speculative. For a long time, headlines warning that “quantum computers will break Bitcoin” were dismissed as hype because the hardware required to carry out such attacks did not exist. The recent developments suggest that industry players now consider the risk credible enough to warrant concrete preparation.
How Bitcoin could be exposed
Bitcoin’s ledger is fully transparent; every transaction can be inspected by anyone. The protection of funds, however, rests on two cryptographic primitives:
- Hash‑based addresses – most Bitcoin wallets store a hash of a public key. The actual public key only appears on‑chain when the associated coins are spent.
- Elliptic‑curve digital signatures (ECDSA) – these verify that a transaction was authorized by the holder of the private key that corresponds to the revealed public key.
A powerful enough quantum computer could, in theory, run Shor’s algorithm to derive the private key from a disclosed public key, then forge a valid signature and move the coins. The vulnerability is therefore tied to the moment a public key becomes visible. Legacy address types (e.g., P2PK) expose the key immediately, while newer formats such as P2PKH and P2WPKH keep it hidden until the first spend. Taproot outputs, on the other hand, embed the public key directly in the script, making them instantly observable.
Consequently, any Bitcoin whose public key has never been revealed remains immune to a direct quantum key‑recovery attack, whereas coins that have already been spent at least once become “low‑hanging fruit” for a future quantum adversary.
Expert assessments on timeline and magnitude
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Cais Manai, chief product officer of the privacy‑focused TEN Protocol, told The Defiant that while quantum computers are the first technology capable of challenging Bitcoin’s “digital gold” reputation, the danger is unlikely to materialise within the current decade. He framed the risk as “well within the investment horizon of anyone calling Bitcoin ‘digital gold’” but not an imminent crisis.
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Chaincode Labs, a prominent Bitcoin research collective, estimated in a May 2025 report that roughly 20‑50 % of all BTC (equating to 4‑10 million coins, worth hundreds of billions of dollars) could be compromised if a sufficiently advanced quantum machine were to appear. Their analysis focused on the subset of coins that already have exposed public keys.
- Manai emphasized that mining acceleration via quantum hardware is a peripheral concern; the primary vector would be private‑key theft. He warned that the “real risk isn’t timing certainty. It’s timing asymmetry.” Upgrading Bitcoin’s consensus rules typically consumes 5‑10 years, while breakthroughs in quantum hardware could occur on an unpredictable trajectory.
Paths to mitigation
Post‑quantum signature schemes such as those being standardized by NIST already exist, but integrating them into Bitcoin would require a hard‑fork and near‑global coordination. The challenge is not technical feasibility but governance: achieving consensus among miners, developers, wallet providers and exchanges is a multi‑year process.
Other blockchain ecosystems are already drafting plans. Optimism, an Ethereum Layer‑2 solution, recently published a decade‑long roadmap to transition users to quantum‑safe wallets, noting that its modular OP‑Stack architecture facilitates swapping signature algorithms. Ethereum co‑founder Vitalik Buterin has also advocated for adopting quantum‑resistant cryptography on the mainnet.
Key takeaways
- Market reaction is growing – Institutional investors and major exchanges are beginning to factor quantum risk into portfolio allocation and operational planning.
- Only exposed public keys are vulnerable – Coins whose addresses have never revealed a public key remain safe under current cryptographic assumptions.
- Potentially half of BTC could be at risk – Research estimates suggest 20‑50 % of circulating Bitcoin may become vulnerable if a capable quantum computer appears.
- Upgrade timelines are long – Even if post‑quantum signatures are ready today, achieving network‑wide adoption in Bitcoin could take a decade or more.
- Coordination asymmetry is the core concern – The speed at which quantum hardware matures may outpace the consensus‑building process required for a protocol upgrade.
- Cross‑chain focus – Ethereum, Optimism and other platforms are already outlining migration paths, indicating that the quantum‑security debate is expanding beyond Bitcoin.
Outlook
While a practical quantum attack on Bitcoin is still considered a medium‑term prospect, the shift from theoretical alarmism to concrete preparatory steps marks a new phase in the crypto industry’s risk management. Stakeholders are now balancing the cost of early mitigation against the uncertainty of quantum timelines, a dynamic that is likely to shape governance discussions and research funding for the next several years.
Source: https://thedefiant.io/news/blockchains/bitcoin-quantum-computing-threat
