An analysis said about 9.6 percent of Bitcoin's (BTC) total supply is structurally unsafe if future quantum computing technology breaks cryptographic systems.

Cointelegraph, a blockchain-focused media outlet, reported on May 20 that on-chain data analytics firm Glassnode analysed that about 1.92 million BTC is locked in address types with public key exposure structures. That is about 9.6 percent of Bitcoin's total supply.

Glassnode said in the analysis that the early design structure of the Bitcoin network and some newer address methods could become potential vulnerabilities in the era of quantum computers.

The largest share was holdings believed to be owned by Satoshi Nakamoto. Glassnode analysed that about 1.1 million BTC estimated to be held by Bitcoin creator Satoshi Nakamoto accounts for 5.5 percent of the total vulnerable supply. It also counted about 620,000 BTC in early Satoshi-era coins at 3.1 percent and about 200,000 BTC in Taproot-based addresses at about 1 percent.

The structures cited were early pay-to-public-key (P2PK), legacy pay-to-multisig (P2MS) and Taproot-based pay-to-taproot (P2TR). These address types are designed to expose public keys or equivalent information. The analysis said that could leave them at risk in the long term if quantum computers neutralise cryptographic systems.

Glassnode assessed that the analysis shows the need for a Bitcoin quantum resistance upgrade. As an alternative, it cited the P2MR output type proposed in BIP-360. The method focuses on removing quantum-vulnerable paths based on Taproot.

It also stressed that the risk of actual theft is not imminent at the current level. A report released in March by U.S. asset manager ARK Invest said breaking Bitcoin’s elliptic curve cryptography (ECC) would require about 2,330 logical qubits and tens of millions to billions of quantum gate operations. That means much higher quantum computing performance than now would be needed for a realistic quantum-based attack.

Glassnode classified about 13,990,000 BTC, or 69.8 percent of total supply, as not exposed to quantum threats. That is similar to ARK Invest’s earlier estimate of about 65 percent as a “safe” amount.

By contrast, about 4,120,000 BTC, or 20.6 percent of the total, was analysed as “operationally unsafe” due to operational reasons such as address reuse or key management issues. Glassnode said this portion could reduce its risk exposure through improvements in address management methods and wallet infrastructure.

Holdings also differed by institution. The analysis found that 100 percent of Bitcoin held by Franklin Templeton, WisdomTree and Robinhood was counted as included in quantum-exposed structures. Revolut was at 99 percent and Grayscale was at about 52 percent. Fidelity, by contrast, had only 2 percent exposure.

Gaps by exchange were also pronounced. About 5 percent of Coinbase-held BTC was exposed, while Binance was at 85 percent and Bitfinex was close to 100 percent, the analysis showed.

Glassnode stressed that exchanges and custodians need to reduce key reuse and tighten address management standards to prepare for future quantum threats. It added that, over the long term, a plan is needed to move to quantum-resistant address systems.

The market views the quantum computer risk as less an immediate reality than a task tied to which upgrade path the Bitcoin network will choose over the long term. In that situation, the analysis could become a reference point for future discussions because it distinguishes which parts of Bitcoin supply are structurally exposed and which parts can be reduced through improved operating practices.