Glassnode Finds 6.04 Million BTC With Exposed Keys Under Quantum Risk

A significant portion of the Bitcoin supply is already vulnerable to a potential future threat from advanced quantum computers, according to a new analysis. Research from blockchain analytics firm Glassnode finds that 6.04 million BTC, representing 30.2% of all issued Bitcoin, has its public cryptographic keys exposed on the blockchain, a prerequisite for a theoretical quantum attack.

The security concern stems from the nature of Bitcoin's encryption. While deriving a private key from a public key is currently impossible for classical computers, a sufficiently powerful quantum computer running Shor's algorithm could, in principle, perform this reversal. Glassnode's analysis focuses on an "at-rest" model, meaning coins are considered exposed if their public key is already visible on the blockchain while the funds remain unspent, requiring no further action from the owner to become a target.

The exposed supply is divided into two categories. Structural exposure, accounting for 1.92 million BTC or 9.6% of the supply, involves coins locked in older script formats that reveal the public key by design. This includes early "pay-to-public-key" outputs from Bitcoin's founding era—some...