A compliant platform: Quantum computing may threaten 6.5 million Bitcoins, accounting for one-third of the total supply.

Source: Yellow Original Title: Coinbase: Quantum Computers Could Compromise 6.51M Bitcoin, One Third of Total Supply

Original Link: A compliance platform’s global investment research director warns that advances in quantum computing pose a structural risk to Bitcoin’s long-term security, with about one-third of the circulating supply potentially at risk due to exposed public keys.

David Duong, the global investment research director at a compliance platform, stated that although the so-called “quantum threat” is not imminent, its arrival is happening faster than many investors expected.

Duong pointed out that growing concerns around quantum computing have begun to appear in regulatory guidelines and institutional disclosures, indicating that the issue is shifting from theoretical to strategic.

Quantum Risk Shifts from Hypothesis to Structural

Duong said the main danger will occur at what researchers call “Q Day,” when cryptography-related quantum computers can perform algorithms like Shor and Grover at sufficient scale to break current cryptographic systems.

Bitcoin relies on two fundamental cryptographic components: elliptic curve digital signature algorithm (ECDSA) to protect transaction signatures, and the SHA-256 hash function that supports proof-of-work mining.

Advances in quantum computing could threaten both, but Duong emphasized that the risk to transaction signatures is the most urgent concern.

According to analysis by a compliance platform, quantum mining capable of significantly disrupting Bitcoin’s economic model remains a lower-priority threat due to scalability limitations.

In contrast, the possibility of deriving private keys from exposed public keys represents a more direct structural vulnerability.

One Third of Bitcoin Supply at Risk

At block height 900,000, Duong estimates that approximately 65 million Bitcoins, or 32.7% of the total supply, could be vulnerable to remote quantum attacks.

These risks mainly stem from address reuse and legacy script types that expose public keys directly on-chain.

Vulnerable categories include Pay-to-Public-Key outputs, simple multisignature scripts (bare multisignature), and Taproot addresses, with early-era coins—often associated with Satoshi-era wallets—forming a notable subset.

Once a public key is exposed on-chain, sufficiently powerful quantum computers could theoretically derive the corresponding private key.

Duong also highlighted a second risk: short-term attacks that could occur during spending.

When transactions enter the mempool and their public keys become visible, all outputs are temporarily exposed, increasing the urgency to migrate to quantum-resistant signature schemes.

Growing Institutional and Regulatory Signals

Duong noted that awareness among institutions is increasing.

In May 2025, a leading asset management firm included quantum computing as a potential long-term risk in its revised disclosure for its Bitcoin Trust ETF.

On the policy front, US and European agencies have begun instructing critical infrastructure providers to plan to transition to post-quantum cryptography by 2035.

While Bitcoin and other open blockchain protocols could theoretically upgrade their cryptography, Duong emphasized that such a transition would require extensive coordination across the ecosystem, including wallets, exchanges, miners, and custodians.

Preparing for a New Security Paradigm

Duong frames this challenge as a preparedness issue rather than a panic one.

He notes that the probability of a successful quantum attack in the short term remains very low, but the scale of potential impact makes proactive planning essential.

He wrote, “The urgency comes from the amount of value locked in cryptographic assumptions that may not be sustainable indefinitely.”

The analysis adds to a growing body of research indicating that Bitcoin’s long-term resilience depends not only on economics and decentralization but also on its ability to adapt cryptographically as computing power advances.