# 6.9 Million Bitcoin at Risk From Quantum Attacks

**Published:** 2026-09-13T11:52:22.811Z  
**Topic:** Bitcoin  
**Sentiment:** neutral  
**Publisher:** TrendWatcher — https://www.trendwatcher.in/article/b9701f14-10b5-40a3-b66d-d3fab3b3a607

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] |

## Exposed Bitcoin Addresses

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].

## Proposed Solutions and Challenges

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].

## What to watch

*   **Bitcoin developer proposals:** Monitor the progress and community consensus around BIP-360 and BIP-361, which aim to introduce quantum-resistant address schemes and migration mechanisms [2].
*   **Quantum computing advancements:** Track developments in quantum computing capabilities, particularly the timeline for building quantum computers powerful enough to break 256-bit cryptographic keys [2, 3].
*   **Migration of funds:** Observe any initiatives or tools that emerge to help Bitcoin holders identify and migrate funds from exposed addresses to quantum-safe alternatives [1, 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.

## Sources
1. 247wallst — [Which Bitcoin Wallets Are at Risk From Quantum Computers?](https://247wallst.com/investing/cryptocurrency/2026/09/12/which-bitcoin-wallets-are-at-risk-from-quantum-computers-6-9-million-btc-have-exposed-keys/)
2. Bitnovo — [The technical plan to protect 6.9 million Bitcoin from quantum...](https://www.bitnovo.com/blog/en/the-technical-plan-to-protect-6-9-million-bitcoin-from-quantum-computing)
3. KuCoin — [What Percentage of Bitcoin Is Actually at Risk from Quantum Attacks?](https://www.kucoin.com/blog/ru-what-percentage-of-bitcoin-is-at-risk-from-quantum-attacks)

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Cite as: TrendWatcher, "6.9 Million Bitcoin at Risk From Quantum Attacks", https://www.trendwatcher.in/article/b9701f14-10b5-40a3-b66d-d3fab3b3a607