Glassnode has quantified a major risk hanging over the Bitcoin network. According to the on-chain analytics firm, roughly 6.04 million BTC - about 30.2% of the total issued supply - is exposed to potential quantum computing attacks because the public keys for those coins are already visible on the blockchain.
The remaining 13.99 million BTC (69.8%) has no public-key exposure at rest, making it structurally shielded for now.
Why public-key visibility matters: Bitcoin's security relies on a one-way relationship between private and public keys. Quantum computers, using Shor's algorithm, could theoretically reverse-engineer a private key from a known public key. If a public key has never appeared on-chain, attackers have nothing to work with.
Structural vs. operational exposure: Glassnode splits the 6.04 million BTC into two categories:
- 1.92M BTC (Structural): Coins in older address formats (P2PK) where the public key is part of the address itself. Many belong to lost wallets or early miners, possibly including Satoshi Nakamoto's holdings.
- 4.12M BTC (Operational): Coins exposed through spending transactions and address reuse. This includes 1.63M BTC tied to exchange balances.
Risk reality: No existing quantum computer can crack Bitcoin's encryption today. Estimates suggest millions of stable qubits are needed, a milestone years away. However, cryptographic transitions take time, and exposed coins cannot be retroactively secured.
Bottom line for investors: Avoid address reuse. Move funds to modern address types like P2WPKH or P2TR where the public key remains hidden until a transaction is made. Exchanges must implement better key rotation to reduce the 1.63M BTC exposure. Bitcoin's governance model faces a long-term strategic question on adopting quantum-resistant signatures.