Quantum Attack on Bitcoin Mining Would Require Star-Scale Energy, Study Says

Bitcoin, Ethereum and other major blockchains rely on elliptic-curve cryptography to authenticate transactions. A sufficiently capable quantum computer could derive private keys from public keys exposed onchain, allowing an attacker to sign valid transfers without breaching a wallet, device or exchange. That distinction matters because “Q-day” — when quantum machines can break standard public-key cryptography — may arrive without the conventional forensic evidence that normally identifies a security intrusion.

Christopher Smith, CEO and co-founder of Quantus Network, said on Aug. 10 that an initial attack could resemble scattered cases of lost or stolen keys. Targets may include Tether’s minting key rather than Satoshi Nakamoto’s Bitcoin holdings, valued at about $63 billion at the time. Google in March accelerated its post-quantum migration target to 2029, while Smith put the odds of cryptography-breaking capability emerging by 2028 at 50%.

Bitcoin relies on elliptic-curve cryptography to authenticate wallet transactions. A sufficiently powerful quantum computer could derive private keys from exposed public keys, allowing an attacker to forge signatures and seize funds. The risk is not immediate, but migration is complex because blockchains must distinguish legitimate owners from attackers after conventional signatures fail. Coinbase’s quantum advisory council said in June 2026 that about 7 million bitcoin could eventually be exposed if holders do not move assets to quantum-safe addresses.

On July 15, 2026, Project Eleven unveiled a post-quantum zero-knowledge proof developed with Jim Posen, lead maintainer of the open-source Binius proof system. The method uses BIP-32 wallet derivation to prove control of key material above an address without revealing it, potentially authorizing recovery into a quantum-safe wallet. On an M5 MacBook Air, the prototype generated a proof in 243 milliseconds using four cores and verified it in 40 milliseconds, with 2.1 GB of peak proving memory. It supports P2PKH, P2WPKH and P2SH-P2WPKH addresses, but remains unaudited and requires protocol-level integration.

Bitcoin transactions rely on elliptic-curve digital signatures. A sufficiently powerful quantum computer could use Shor's algorithm to derive a private key from a public key, leaving older addresses whose keys have already been exposed at greatest risk. A February 2026 estimate put nearly 7 million BTC at risk, including about 1 million attributed to Satoshi Nakamoto, with a combined value of about $440 billion. The issue has implications for holders' property rights and consensus across the network.

On June 13, 2026, an independent quantum computing advisory board convened by Coinbase said quantum computers could not yet break Bitcoin but urged immediate planning for quantum-resistant signatures. It estimated that about 6.7 million BTC was at risk but did not endorse freezing or restricting older coins. A May 6 report from Project Eleven set 2033 as its baseline year for Q-Day, with 2030 as the earliest scenario.

Bitcoin transactions use elliptic-curve digital signatures to secure assets. A quantum computer running Shor’s algorithm could potentially derive private keys from public keys, putting older wallets and transaction security at risk. Ethereum, by contrast, has planned a mechanism allowing accounts to adopt quantum-resistant signatures, bringing corporate crypto treasury strategies and onchain governance capabilities into focus.

Google Quantum AI and other institutions published research on March 30, 2026, estimating that fewer than 500,000 physical qubits could crack a key in about nine minutes. Citi warned on May 18 that the potential attack timeline had shortened. Bit Digital had already announced on July 7, 2025, that it would sell about 280 Bitcoin and, alongside a $172 million fundraising, increase its holdings to 100,603 Ethereum.

Bitcoin uses elliptic-curve cryptography to protect assets and communications, but sufficiently powerful quantum computers could eventually break its current encryption. Experts say the more immediate danger is a “harvest now, decrypt later” strategy, in which attackers intercept and store large volumes of encrypted communications today, then recover sensitive historical data once the technology matures. The threat extends beyond wallet private keys.

Security experts and an early-stage venture investor have recently warned that historical communications and infrastructure data across the Bitcoin ecosystem may already be targets for quantum attacks. Ethereum has begun work on a post-quantum migration, but as of this report, neither Bitcoin nor related companies had publicly committed to specific safeguards, disclosed investment amounts or set completion dates. The upgrade timetable and division of responsibility therefore remain unclear.

Bitcoin and Ethereum rely on elliptic-curve cryptography to safeguard assets. A quantum computer capable of deriving a private key from a public key could potentially steal funds. Bitcoin activated Taproot on November 14, 2021, and because some transactions expose public keys in advance, the potential window for attack has widened.

The latest research from Google Quantum AI estimates that about 500,000 error-corrected physical qubits could be enough to crack a key within Bitcoin’s roughly nine-minute transaction confirmation window, far below previous estimates of several million qubits. No funds have been reported stolen through such an attack, but the researchers are urging the community to begin planning a migration to post-quantum cryptography.

Bitcoin transactions rely on elliptic-curve digital signatures. A sufficiently powerful quantum computer running Shor’s algorithm could derive private keys from exposed public keys and steal assets. Replacing the signature mechanism would require network-wide consensus and asset migration, drawing attention to StarkWare’s upgrade-free approach as a fallback until longer-term changes such as BIP-360 are completed.

On April 9, 2026, StarkWare Chief Product Officer and BIP-360 co-author Avihu Levy published the QSB paper and open-source code. The system uses Bitcoin’s existing Script constraints and hash-based proofs to create quantum-resistant transactions without a soft fork or miner activation. Each transaction requires substantial offline GPU computation at an estimated cost of $75–$200, and the tool is currently intended for emergency recovery.

Quantum computers capable of breaking public-key cryptography could threaten Bitcoin signatures and asset ownership, making the technology a long-term market risk. Strategy, formerly MicroStrategy, co-founder and Executive Chairman Michael Saylor said banks, the internet and crypto assets all face the same pressure to upgrade, while Bitcoin could adopt quantum-resistant cryptography through updates to its nodes, wallets and protocol.

Saylor told Natalie Brunell’s “Coin Stories” on Feb. 23, 2026, that any quantum breakthrough posing a material threat was at least 10 years away. At a Mizuho event on April 8, he again said the risk was overstated and could be addressed through upgrades. He also said Bitcoin had likely bottomed at about $60,000 in early February; its price was around $71,200 when the report was published on April 9.

Quantum computers could theoretically derive private keys from public keys exposed on-chain, allowing attackers to forge signatures and steal assets. Cybersecurity organization Project Eleven estimates that about 7 million Bitcoin may face long-term exposure, worth roughly $470 billion at recent prices. Most wallets whose public keys have not been revealed are currently unaffected, however, meaning the risk does not extend across the entire network.

Galaxy Digital research head Alex Thorn said on March 19, 2026, that the quantum threat was real but did not yet pose an existential crisis for Bitcoin. Research analyst Will Owens added on March 20 that related proposals had increased markedly since late 2025. Developers are advancing quantum-resistant addresses, BIP 360 and phased upgrade plans, while investors should currently view the issue as a long-term technical challenge.

Bitcoin relies on elliptic-curve digital signatures to secure asset ownership, but powerful quantum computers could eventually derive private keys from public keys that have already been exposed. ARK Invest and Bitcoin financial services provider Unchained therefore studied advances in quantum technology and potential paths for Bitcoin to adopt quantum-resistant cryptography, an issue with implications for long-term asset security and consensus on network upgrades.

On March 11, 2026, ARK Invest and Unchained published the “Bitcoin and Quantum Computing” white paper, estimating that 34.6%, or about 6.9 million BTC, is theoretically at risk. That includes about 1.7 million BTC believed to be lost and roughly 5.2 million BTC that could be moved to more secure addresses. The report said the threat would emerge in stages and was not urgent in the near term, leaving the community time to deploy quantum-resistant solutions.