Glassnode: 6.26 Million BTC Face Potential Quantum Computing Risks From Public-Key Exposure

Approximately 6.26 million Bitcoin, representing 31.2% of the cryptocurrency’s total supply, are held in addresses with publicly exposed public keys, according to figures shared by Glassnode co-founder Rafael. The data highlights a growing area of long-term concern for Bitcoin holders as researchers examine how advances in quantum computing could affect existing cryptographic systems.

The reported share has increased from 24.8% in early 2021, indicating that a larger proportion of Bitcoin supply now falls into categories where public keys are visible on-chain. However, public-key exposure does not mean these coins have been compromised, nor does it establish that an attacker currently has the technology needed to steal them.

Rafael emphasized that the figures measure on-chain public-key exposure rather than confirmed attacks or the overall security of cryptocurrency platforms. The distinction is important because quantum-related risk depends on the cryptographic structure of an address, the availability of its public key and the capabilities of a potential attacker.

Address Reuse Accounts for Most Exposed Bitcoin

Of the approximately 6.26 million BTC identified, around 4.33 million BTC are associated with address reuse, according to the figures. When Bitcoin is spent from an address, its public key can become visible on the blockchain. Reusing an address can therefore leave that key publicly available for longer, depending on how the address has been used.

Another approximately 1.94 million BTC are classified as directly exposed through script types such as Pay-to-Public-Key (P2PK) and Taproot. These categories differ in how public keys are represented or revealed, so they should not all be treated as having identical technical risk profiles.

The two reported categories total roughly 6.27 million BTC, slightly above the stated 6.26 million BTC headline figure. This small discrepancy may reflect rounding or differences in the underlying estimates, and the figures should be understood as approximate rather than exact accounting totals.

Quantum computing concerns center on whether a sufficiently capable machine could use exposed public-key information to derive the corresponding private key. Bitcoin currently relies on cryptographic methods that are considered secure against conventional computers, but a sufficiently advanced, fault-tolerant quantum computer could threaten some of those protections. No claim in the reported figures establishes that such a machine is presently capable of stealing the identified BTC.

Exchange Holdings Also Show Significant Exposure

The figures also identify approximately 1.79 million BTC held by exchanges as having exposed public keys. That amount represents around 57% of the exchange holdings included in the analysis, up from 55% in May this year.

The exchange figure adds another dimension to the discussion because trading platforms hold substantial Bitcoin balances on behalf of customers. Nevertheless, public-key exposure alone does not show that an exchange has suffered a breach, mishandled customer assets or faces an immediate loss of funds.

Rafael specifically cautioned that the statistics should not be interpreted as a security assessment of exchanges or custodians. Assessing a platform’s overall security would require information beyond public blockchain data, including its key-management practices, operational controls and asset-storage arrangements.

For individual Bitcoin holders, the data reinforces the value of understanding address reuse and following developments in post-quantum cryptography. Future mitigation could involve protocol upgrades and migration to cryptographic systems designed to resist quantum attacks, although implementation would require careful technical and ecosystem coordination.

The central takeaway is that 6.26 million BTC reportedly sit in address categories relevant to long-term quantum risk, not that nearly one-third of Bitcoin has already been hacked or is certain to be stolen. The figures offer a snapshot of public-key exposure as debate over Bitcoin’s long-term cryptographic resilience continues.