Researcher Warns 6.9 Million BTC Are Vulnerable to Quantum Attack
A new analysis from Project 11 CEO Alex Pruden has significantly escalated concerns over Bitcoin's security against future quantum computing threats. On February 11, 2026, Pruden stated that approximately 6.9 million BTC reside in legacy addresses that are potentially vulnerable to quantum attacks. This figure dramatically revises the scale of the risk compared to previous industry assessments.
Pruden's estimate directly challenges a prior analysis from CoinShares, which had concluded that only 10,200 BTC were held in "genuinely" quantum-vulnerable addresses. The nearly 700-fold increase in the estimated exposure reframes the issue from a niche technical concern to a systemic risk affecting a substantial portion of Bitcoin's total supply.
Legacy Address Security Poses Long-Term Challenge
The core of the vulnerability lies with legacy Bitcoin addresses, which are more susceptible to attacks once their public keys are exposed. Pruden's argument hinges on the possibility that functional quantum computers could emerge "sooner than the market expects," creating an urgent need for security upgrades for assets held in these older account types.
This revised risk assessment could trigger significant concern among institutional investors and long-term Bitcoin holders who may have assets in these legacy wallets. The research is likely to accelerate development and advocacy for migrating funds to quantum-resistant addresses and may create negative market sentiment if the narrative gains traction among investors.
