More than 6 million bitcoin — 31.2% of the entire circulating supply — now sit behind exposed public keys visible directly on the blockchain, according to new data from on-chain analytics firm Glassnode. The finding lands just a day after Ethereum researcher Justin Drake urged the crypto industry to prepare for "bunker mode," warning that artificial intelligence could crack wallet cryptography far sooner than most expect.
What the New Glassnode Data Shows
Glassnode co-founder Rafael Schultze-Kraft reports that bitcoin's publicly visible key supply has grown by 222,000 BTC — about $18.2 billion at current prices — since the firm's May 2026 report, even though total bitcoin supply increased by only 64,000 BTC over the same period. That means exposure is growing roughly three and a half times faster than new coins are being mined, a gap Schultze-Kraft flagged as a sign that address reuse and legacy transaction formats are quietly widening the risk pool.
Today's 31.2% reading sits five to six percentage points above the cycle low recorded in 2023, reversing several years of gradual improvement in on-chain key hygiene.
Why Exposed Public Keys Matter for Bitcoin Security
A bitcoin address with an exposed public key is not automatically unsafe under today's technology, and no practical attack on Bitcoin or ether wallet keys has ever been demonstrated. But a visible public key is one of two pieces of information that a sufficiently advanced quantum computer, or a hypothetical mathematical shortcut, could theoretically use to derive a wallet's private key. Addresses that have never revealed a public key carry no such theoretical exposure, which is why analysts treat the 31.2% figure as a measure of latent risk rather than an active threat.
Public keys typically become visible through address reuse — spending twice from the same address — or through newer output types, including early pay-to-public-key formats and Bitcoin's Taproot upgrade, that publish the key by design.
How Exposure Varies Across Exchanges and Custodians
The breakdown shows sharp differences in how carefully major holders manage this risk. Exchanges collectively hold 1.79 million BTC behind visible public keys, with Coinbase's share at a conservative 10% compared with 83% at Binance. Among non-exchange custodians, Fidelity holds roughly 375,000 BTC with just 2% exposed, while Grayscale sits at 49%, Revolut at 99% and Robinhood at a full 100%. Government-held bitcoin in the U.S., U.K. and El Salvador shows no exposure under Glassnode's methodology, reflecting far more conservative custody practices for sovereign reserves.
The AI Threat Timeline Behind the "Bunker Mode" Warnings
The renewed scrutiny follows Justin Drake's warning that AI could potentially find a shortcut to breaking wallet cryptography "in months, not years" in a worst-case scenario, well before quantum computers pose a practical threat. Ethereum co-founder Vitalik Buterin echoed similar concerns this week about AI-driven mathematical breakthroughs threatening lattice-based cryptography, the foundation of several post-quantum signature standards now being built into Ethereum's long-term roadmap.
What Bitcoin Holders Should Do Now
Security researchers tracking this data generally recommend the same low-cost precautions regardless of timeline: avoid reusing bitcoin addresses, move funds to fresh addresses that have never broadcast a transaction, and treat any address with a known exposed public key as a candidate for rotation. None of it requires panic-selling or jumping to a different blockchain — it simply shrinks the pool an eventual attacker, AI-assisted or otherwise, would have to work with.
For now, the 31.2% figure is a reminder that bitcoin's cryptographic safety margin is a moving target, not a fixed guarantee — and the gap is widening at a pace worth watching closely over the coming months. Readers can follow ongoing coverage of this story on CryptoCloudNews.