Can Quantum Computing Actually Break Bitcoin?

KEY TAKEAWAYS

1. Google Quantum AI published a March 2026 whitepaper estimating that breaking Bitcoin's ECDSA 256 encryption requires 20 times fewer qubits than previously projected in 2019.
2. Roughly 6.9 million BTC, approximately 32% of the total supply, sit in wallets with public keys already exposed on the chain.
3. Researcher Giancarlo Lelli cracked a 15-bit elliptic curve key on 24 April 2026, winning a 1 BTC bounty from quantum security firm Project Eleven.
4. Blockstream CEO Adam Back estimates the practical quantum threat remains 20 to 40 years away, contradicting more aggressive timelines projected by Google research teams.
5. Bitcoin developers proposed BIP 360, a quantum-resistant address standard, though full network migration to post-quantum cryptography may require five to seven years.

Google's Quantum AI team published a whitepaper on 31 March 2026 that changed the conversation about Bitcoin's long-term security. The research showed that breaking Bitcoin's elliptic curve cryptography could require fewer than 500,000 physical qubits, roughly 20 times fewer than 2019 estimates suggested, according to altFINS. Current quantum hardware operates far below that threshold. This article separates the genuine risk from the hype, examining what Google's research actually shows, which coins face exposure, and what Bitcoin developers are doing about it.

What Google's 2026 Research Actually Found

Google Quantum AI modeled a real-time transaction hijacking attack against Bitcoin's 10-minute block confirmation window. The attack achieved a 41% success rate in simulation. The research identified approximately 6.9 million BTC sitting in wallets where public keys are already visible on the chain, CoinDesk reported.Those exposed wallets include Satoshi Nakamoto's early holdings and coins whose public keys have been revealed through spending. Satoshi's coins alone represent over 1 million BTC. Public-key exposure can occur when coins are spent from address types that reveal the key, while Taproot outputs expose their public keys even before spending.Dan Boneh, a Stanford cryptographer and co-author of the Google paper, warned against rushing Bitcoin into a post-quantum migration. "A hasty transition to post-quantum is more likely to cause a catastrophic bug than we'll be attacked by a quantum computer," Boneh said, per crypto.news reporting. The comment highlights a core tension between speed and safety.

How Far Away is the Actual Threat

On 24 April 2026, researcher Giancarlo Lelli cracked a 15-bit elliptic curve key using publicly accessible quantum hardware. He won a 1 BTC bounty from quantum security firm Project Eleven, Intellectia reported. That represents a 512-fold improvement over the previous September 2025 demonstration.Bitcoin uses 256-bit encryption, and the gap between 15 bits and 256 bits remains enormous. Blockstream CEO Adam Back argues the practical threat sits 20 to 40 years in the future. ARK Invest's March 2026 report concluded that quantum computing remains at Stage 0, meaning hardware exists but lacks commercially relevant capability.IBM targets 200 logical qubits by 2029 through its Starling program. Google set a 2029 internal deadline to migrate its own infrastructure to post-quantum cryptography. Expert consensus now places a cryptographically relevant quantum computer between 2030 and 2040, compressing from earlier estimates that stretched past mid-century.

Bitcoin's Defense: BIP 360 and the Migration Challenge

Bitcoin developers have proposed BIP 360, which defines a Pay-to-Merkle-Root (P2MR) output type designed to reduce exposure to quantum attacks. The proposal removes the quantum-vulnerable key-path spend and commits to a Merkle root of scripts, keeping the public key off-chain until the coins are spent. Post-quantum signature schemes themselves are left to a separate future BIP.Ethereum has moved faster on this front. Vitalik Buterin published a quantum emergency roadmap that allows individual accounts to switch to quantum-resistant signatures independently. No network-wide vote would be required, Forbes noted. Bitcoin's more conservative upgrade culture may slow its response.NIST's roadmap calls for deprecating current encryption standards by 2030. Standardized quantum-resistant algorithms already exist. The challenge is deploying them across a decentralized network where no central authority can mandate upgrades to millions of independent users and wallet providers.

Regulatory Implications

In January 2026, Jefferies strategist Christopher Wood removed a 10% Bitcoin allocation from his model portfolio, citing quantum risk. An industry coalition declared 2026 the Year of Quantum Security, with officials from the FBI, NIST and CISA participating in the January launch. Government migration timelines could pressure institutional Bitcoin holders to demand faster cryptographic upgrades.

What's Next?

Google and IBM target 1 million physical qubits by the early 2030s. BIP 360 development continues with community review. Quantum computing cannot break Bitcoin today, but the timeline has compressed significantly. All assessments discussed remain speculative. Investors should evaluate quantum risk within their broader portfolio framework independently.

FAQs

Can quantum computers break Bitcoin today? No, current quantum hardware operates far below the threshold needed to crack Bitcoin's 256-bit elliptic curve cryptography, according to multiple research assessments.How many qubits are needed to break Bitcoin? Google's March 2026 research estimated fewer than 500,000 physical qubits would be required, roughly 20 times fewer than previously projected in 2019.How much Bitcoin is at risk from quantum attacks? Approximately 6.9 million BTC, about 32% of total supply, sit in wallets with exposed public keys vulnerable to future quantum computing attacks.What is BIP 360? BIP 360 defines a new Bitcoin output type, Pay-to-Merkle-Root (P2MR), that works like Taproot but removes the quantum-vulnerable key-path spend, so the public key stays off-chain until the coins are spent. Post-quantum signature schemes themselves are left to a separate future BIP.When could quantum computers threaten Bitcoin? Expert timelines range from the early 2030s to mid-century, with Google's 2029 migration deadline suggesting the threat is plausible within this decade.Is Ethereum safer than Bitcoin from quantum threats? Ethereum's faster upgrade process and Vitalik Buterin's emergency roadmap may allow quicker migration, though both networks use vulnerable elliptic curve cryptography today.Did anyone crack Bitcoin encryption with a quantum computer? Researcher Giancarlo Lelli cracked a 15-bit key in April 2026, but Bitcoin uses 256-bit encryption, leaving an enormous gap before practical vulnerability.

References

1. altFINS Can Quantum Computers Break Bitcoin, Google 2026 Research
2. CoinDesk Bitcoin Quantum Threat
3. Intellectia Bitcoin Quantum Computing Threat 2026
4. Forbes Bitcoin's Quantum Deadline