Quantum Computing Threatens Bitcoin Security as Bit Digital Shifts to Ethereum

Bitcoin uses elliptic-curve digital signatures to protect private keys and authorize transactions. If a large-scale quantum computer could use Shor’s algorithm to break public-key cryptography, assets could be transferred without authorization. The threat extends beyond Bitcoin, forcing Web3 to reassess the underlying security of wallets, nodes and cross-chain protocols.

The latest assessments indicate that quantum computers could threaten the security of Bitcoin private keys within the next 5–8 years. The Web3 ecosystem is therefore accelerating adoption of the post-quantum cryptography standards published by the U.S. National Institute of Standards and Technology (NIST) in August 2024. Reports have not disclosed the cost of the migration or a firm completion date.

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 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.

Quantum computers capable of using Shor’s algorithm to break elliptic-curve cryptography could put Bitcoin holdings with exposed public keys at risk of theft. The threat could also extend to internet and financial infrastructure. Citi said Bitcoin’s conservative governance and the need for community consensus on upgrades could leave its migration to quantum-resistant technology trailing Ethereum’s.

Citi issued a digital-assets research report on May 18, 2026, warning that quantum computing breakthroughs are shortening the timeline for a practical attack. The report estimated that the public keys of about 6.5 million to 6.9 million Bitcoin, roughly one-third of the circulating supply, had already been exposed on-chain. Those holdings were worth about $450 billion at prices prevailing at the time.

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 currently relies on ECDSA and Schnorr signatures to secure asset ownership. A sufficiently powerful quantum computer could eventually use Shor’s algorithm to derive private keys from exposed public keys. Although the threat remains confined to laboratory experiments, migrating the network’s wallets, software and users would take considerable time, making early development of quantum-resistant safeguards critical to asset security.

Speaking at Paris Blockchain Week on April 16, 2026, Blockstream CEO Adam Back advocated introducing an optional upgrade first and giving users 10 years to move funds to quantum-resistant addresses. He estimated that a real threat remains at least 20 years away. Blockstream’s research division proposed a hash-based signature scheme in December 2025. The migration could also clarify whether the roughly 500,000 to 1 million Bitcoin attributed to Satoshi Nakamoto can still be moved.

Bitcoin uses elliptic-curve digital signatures to prove asset ownership. If a large-scale quantum computer could use Shor's algorithm to derive private keys, older addresses whose public keys have been exposed could be vulnerable to theft. Wall Street research and brokerage firm Bernstein said the risk is concentrated in Satoshi-era wallets holding about 1.7 million BTC, rather than posing an immediate threat to mining or the entire network.

Bernstein said on April 8, 2026, that Google had cut its estimate of the number of qubits needed to break the cryptography by about 20-fold to fewer than 500,000, but Bitcoin still had three to five years to upgrade. On April 13, the firm said BTC's nearly 50% retreat from its October 2025 peak of $126,198 had already priced in most of the quantum risk. The real challenge, it said, lies in securing community consensus and migrating wallets.

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.

Bitcoin and Ethereum both rely on elliptic-curve cryptography to secure transaction signatures. A practical quantum computer running Shor's algorithm could potentially derive private keys from public keys. Although the threat is not imminent, migrating on-chain assets and coordinating network-wide upgrades would take years. The two communities' ability to replace their cryptographic systems will therefore shape long-term security and market confidence.

On March 26, 2026, Castle Island Ventures partner Nic Carter criticized Bitcoin's slow response. ARK Invest estimated on March 11 that one-third of BTC was at risk. Ethereum has established a post-quantum roadmap for 2029, while Google has also set 2029 as its migration deadline. Bitcoin, meanwhile, is still discussing BIP-360.

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.