4.9M BTC ($455B) exposed to quantum risk via address reuse, up 16% since 2020

On January 20, 2026, analysis showed about 4.9 million BTC—valued at over $455 billion—are vulnerable to potential quantum attacks due to address reuse, up 16% since 2020. Address reuse exposes public keys on-chain, expanding the attack surface even though no powerful quantum computer is publicly available.