Glassnode has flagged a quantum computing vulnerability affecting approximately 10% of Bitcoin's circulating supply. The analytics firm identifies these coins as "structurally unsafe" due to their exposure through reused public key addresses.

The issue centers on address reuse. When Bitcoin holders spend coins from an address, they expose their public key on the blockchain. Quantum computers with sufficient processing power could theoretically derive private keys from these exposed public keys, threatening fund security. Glassnode's analysis reveals roughly 1.8 million BTC exists in this vulnerable state.

This exposure accumulates over time. Early Bitcoin addresses reused for multiple transactions broadcast their public keys repeatedly, creating larger attack surfaces. Many dormant wallets from Bitcoin's early years contain these patterns. Whale addresses, particularly those inactive for years, represent concentrated risk pools.

The vulnerability isn't new but remains unresolved. Quantum computers capable of breaking Bitcoin's elliptic curve cryptography (ECDSA) don't yet exist at scale. Experts estimate such machines remain years or decades away. However, the "harvest now, decrypt later" threat looms. Attackers could record Bitcoin transactions today and decrypt them once quantum capabilities mature.

Glassnode points to BIP-360 as a potential solution. This Bitcoin Improvement Proposal outlines a quantum-resistant upgrade path using post-quantum cryptographic algorithms. However, implementing network-wide changes requires broad community consensus and technical coordination. Bitcoin's immutability and conservative upgrade process complicate rapid quantum-proofing.

The 10% figure deserves scrutiny. Not all reused addresses face equal risk. Some belong to active traders regularly creating new receiving addresses through wallet rotation. Others sit dormant, their private keys potentially lost. Exchanges and custodians hold portions of vulnerable supply, adding institutional risk layers.

Market participants haven't panicked over quantum threats.