Glassnode Says Nearly 10% of Bitcoin Supply Faces Structural Risk From Quantum Breakthrough

Bitcoin transactions use elliptic-curve digital signatures to protect assets. Once an address reveals its public key, a sufficiently powerful quantum computer could eventually derive the private key and steal the funds. The threat is not exploitable today, but the permanent public record of blockchain data means exchanges and long-term holders must plan ahead to migrate to quantum-secure addresses.

Coinbase’s independent advisory board on quantum computing and blockchain released a report on June 11, 2026, estimating that the public keys for about 7 million BTC have been exposed. About 1.7 million BTC are held in early P2PK addresses, while roughly 5 million BTC are exposed through address reuse and largely consist of active funds such as exchange cold wallets. Attackers can collect the data now and attempt to crack it later.

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.

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 currently protects assets with ECDSA and Schnorr signatures. If a large-scale quantum computer could run Shor’s algorithm, it might be able to derive private keys from public keys that have already been exposed. Project Eleven estimates that about $2.3 trillion in assets is at risk, making a post-quantum migration critical to the security of the entire wallet, exchange and custody ecosystem.

Project Eleven CEO Alex Pruden told CoinDesk’s Consensus Miami on May 6, 2026, that Bitcoin developers should immediately move post-quantum signatures from research into production. The Taproot upgrade took about five years and migration was voluntary. A new approach would require participation from all holders, wallets, exchanges and institutions, while BIP-360 has already laid the groundwork for a quantum-resistant output type.

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.

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.