ARK Invest and Unchained have jointly published a white paper evaluating how much of the current Bitcoin supply could be compromised by advances in quantum computing. Both ARK Invest, a leading asset manager focusing on disruptive innovation, and Unchained, a US-based bitcoin financial services provider, regularly contribute research to the digital asset sector. Their new paper addresses the potential security risks quantum computers could pose to Bitcoin’s underlying cryptography.
Distribution Of Bitcoin’s Quantum Exposure
According to the analysis, approximately 34.6% of all existing bitcoins, a significant portion of the circulating supply, are still exposed to a possible quantum attack. This risk primarily arises from how the coins are stored and the visibility of their public keys. The report breaks down the exposure as follows: roughly 5 million BTC—about 25% of the total—are linked to addresses that have reused public keys, making them susceptible to a future cryptographic breach. In addition, about 1.7 million BTC, categorized as likely lost, reside in older pay-to-public-key (P2PK) addresses, which are more vulnerable due to direct public key linkage. Another 200,000 BTC are reported exposed through pay-to-taproot (P2TR) address types.
In contrast, 65.4% of the bitcoin supply is considered not vulnerable under current conditions. These assets are protected by more secure wallet types or have never exposed their public keys on the blockchain, reducing the risk of quantum decryption.
Advances In Quantum Computing And Potential Countermeasures
The white paper focuses on the timeline for potential quantum breakthroughs. It states that for quantum computers to break Bitcoin’s elliptic curve cryptography (ECC)—which secures private keys—machines would need around 2,330 logical qubits, along with tens of millions to billions of quantum gate operations. The authors present a staged development model for quantum progress and indicate that practical attacks within Bitcoin’s average block time would only be viable in the final stage of this evolution.
Based on industry estimates from Google, IBM, and Microsoft, the authors suggest that the first instance of a public key hack could be possible in the mid-2030s. PsiQuantum, a quantum technology company based in Chicago and funded in part by BlackRock, plans to install a one-million-qubit quantum system by 2027, which would be a major milestone but remains below the threshold for threatening Bitcoin’s core security.
In anticipation of future risks, ARK Invest’s report recommends that Bitcoin transition to quantum-resistant address formats over time. The document refers to cryptographic alternatives such as lattice-based ML-DSA and hash-based SLH-DSA, highlighting these as promising standards under post-quantum cryptography. It also discusses a draft protocol improvement—BIP-360—that suggests a new transaction output type to reduce quantum vulnerabilities even without quantum-secure digital signatures.
Chris Tam of BTQ Technologies, a company specializing in quantum security, commented that quantum-resistant digital signatures play a critical role in long-term security planning.
Such signatures are “essential for any meaningful long-term defense against quantum attacks.”
The paper also notes that for Bitcoin protocol upgrades to take place, consensus among network participants, typically through a soft fork, is required. The timeline and implementation of any quantum-resilient measures will hinge on collective agreement within the Bitcoin community and its stakeholders.
