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Approximately 6.9 million Bitcoin, or 30% of circulating supply, are vulnerable to quantum attacks due to exposed public keys, a Google study found.
Approximately 6.9 million Bitcoin (BTC), representing about 30% of the total circulating supply, are held in addresses where their public keys are exposed, making them potentially vulnerable to future quantum computer attacks [3]. This exposure could allow a sufficiently powerful quantum computer to derive private keys and drain funds, posing a systemic risk to the Bitcoin ecosystem [2].
| At a glance | |
|---|---|
| Bitcoin at risk | 6.9 million BTC [1] |
| Percentage of supply | ~30% [3] |
| Value at risk | Over $70 billion [3] |
| Catalyst | Google Quantum AI's March 2026 paper [1] |
The vulnerability stems from the Elliptic Curve Digital Signature Algorithm (ECDSA) used by Bitcoin, which is susceptible to quantum attacks once a public key is visible on-chain [3]. A March 2026 study by Google Quantum AI identified 6.9 million Bitcoin in such addresses, where the full public key is already exposed [1]. This includes about 1.7 million BTC in early P2PK (pay-to-public-key) addresses, many of which are considered lost or Satoshi-era coins and cannot be migrated [1, 2]. The remaining exposed coins are primarily in P2PKH (pay-to-public-key-hash) addresses that have been used for at least one transaction, which publishes the full public key on-chain [1]. Taproot addresses, introduced in November 2021, also expose the public key from creation [1].
In contrast, addresses like P2PKH, P2WPKH, P2SH, or P2WSH that have never signed a transaction only store a hash of the public key, keeping the key hidden and thus protected from this specific quantum attack vector [1]. Ethereum faces a similar issue, with about 20.5 million ETH in exposed accounts, representing roughly a sixth of its circulating supply [1].
The developer community has proposed solutions to address the quantum threat, including BIP-360 for quantum-resistant address schemes and BIP-361 for a progressive migration framework [2]. BIP-360 aims to protect future transactions by creating new, secure address types (P2MR), while BIP-361 outlines a plan for users to transfer existing funds to these new structures [2]. Google projects its post-quantum transition for 2029, and NIST for around 2035, but Bitcoin has not yet ratified a comparable upgrade [1, 2].
A significant challenge lies in how to handle inactive or lost Bitcoin that are not migrated in time [2]. Proposals such as migration deadlines or freezing vulnerable addresses could prevent theft but conflict with Bitcoin's core principles of immutability and non-confiscation [2]. A mass theft of these dormant coins could severely impact Bitcoin's value and market confidence [2].
The debate over quantum preparedness highlights a tension between ensuring the long-term security of Bitcoin and upholding its foundational principles of decentralization and immutability.
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AI-assisted synthesis by the TrendWatcher Editorial Desk · sourced from 3 outlets · Sep 13, 2026 · How we report
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