Measuring Bitcoin's Quantum-Exposed Supply

Crypto Insight Summary: Glassnode researchers Rafael Schultze-Kraft, Kilian Heeg, and CryptoVizArt published an analysis on May 20, 2026, measuring the portion of Bitcoin's supply vulnerable to quantum attacks at rest. They find that 6.04M BTC (30.2% of issued supply) currently has its public key exposed on-chain, while 13.99M BTC (69.8%) does not. Exposure is split into structural (1.92M BTC, 9.6%), where script types like P2PK, P2MS, and Taproot P2TR reveal public keys by design, and operational (4.12M BTC, 20.6%), where address reuse or partial spending has made public keys visible. Within the operational bucket, exchange-related balances account for 1.66M BTC (8.3% of total supply, roughly 40% of all operational exposure), with about half of labeled exchange balances falling into the susceptible category. Custodian-level data shows stark differences: Coinbase has only 5% of its labeled balances exposed, while Binance and Bitfinex show 85% and 100%, respectively. The analysis notes that Satoshi-era coins in the structural bucket are effectively immobile, whereas operational exposure could be reduced through improved wallet and custody practices. BIP-360's proposed Pay-to-Merkle-Root (P2MR) output is cited as a potential mitigation for Taproot's structural exposure, though it would not retroactively protect existing P2TR Crypto Insight Analysis: Direction: Neutral Impact: Minor Impact Horizon: Long-term (1 quarter-1 year) Reasoning: Quantum exposure concerns are long-term but unlikely to impact market sentiment immediately.