One-Third of All Bitcoin Could Be Stolen by Quantum Computers — Here’s Why

TLDR

• Glassnode research shows 6.04 million BTC — 30.2% of supply — is vulnerable to quantum attacks
• Over $469 billion in Bitcoin has had its public cryptographic key exposed on-chain
• Exchanges like Binance and Bitfinex show 85% and 100% quantum exposure respectively
• Startup AmericanFortress has raised $8 million to develop a post-quantum fix using zero-knowledge proofs
• The fix could protect Satoshi’s 1.1 million BTC and nearly 5 million more dormant coins without mass migrations

Nearly one-third of all Bitcoin in circulation is already vulnerable to theft if quantum computers reach the power needed to crack current encryption, according to new research from blockchain analytics firm Glassnode.

The firm analyzed the Bitcoin blockchain to find which coins have had their public cryptographic keys exposed. It found 6.04 million BTC — worth over $469 billion — is at quantum risk. The remaining 13.99 million BTC shows no public key exposure.

How the Vulnerability Works

Bitcoin security relies on private keys matched to public keys. Under normal conditions, a public key is not visible on-chain. But once it is revealed through a transaction or address reuse, a sufficiently powerful quantum computer could use Shor’s algorithm to reverse-engineer the private key and steal the funds.

Glassnode splits the exposed supply into two groups. Structural exposure covers 1.92 million BTC, or 9.6% of supply. These include early “pay-to-public-key” outputs linked to Bitcoin’s pseudonymous creator Satoshi Nakamoto, legacy multisig setups, and Taproot outputs.

Operational exposure is the larger category at 4.12 million BTC, or 20.6% of supply. These coins became vulnerable through address reuse, where repeated transactions at the same address eventually broadcast the public key.

Exchanges make up a large part of this risk. Around 1.66 million BTC of the operational exposure is exchange-related. Coinbase shows only 5% exposure among its labeled balances. Binance and Bitfinex show 85% and 100% respectively. Glassnode stressed this reflects custody design choices, not a solvency warning.

Sovereign Bitcoin holdings fared better. The United States, United Kingdom, and El Salvador all show zero quantum exposure.

A Proposed Fix

Startup AmericanFortress says it has a solution. The company, backed by an $8 million seed round, has developed a patent-pending post-quantum signature scheme using zero-knowledge proofs.

The protocol would not require mass fund migrations or new blockchains. Instead, it uses a backward-compatible soft fork to freeze and protect dormant wallets — including Satoshi-era addresses that cannot be upgraded automatically.

The fix applies to Bitcoin, Ethereum, Solana, and Tron. For active users, upgrading takes around 50 milliseconds via a wallet prompt. The company says the cost is roughly equal to one rollup transaction.

AmericanFortress claims over $600 billion in crypto assets sit in a vulnerable state, including 100% of Solana addresses. Its cryptographic methods for Bitcoin are expected to be ready for public discussion within weeks, ahead of a formal presentation on June 2 in Paris.

Separately, the Bitcoin developer community is debating BIP-360, a proposal to introduce quantum-resistant transaction formats. Estimates for “Q-Day” — when a quantum computer powerful enough to crack Bitcoin’s encryption could exist — range from 2030 to 2032. The US government announced this week it will invest over $2 billion into quantum computing startups.

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