According to Glassnode, the public keys of 7.12 million BTC, equivalent to 35.4% of Bitcoin in circulation, are visible and could be targeted by sufficiently powerful quantum computers in the future.
An analysis published by Glassnode on November 10 measures a potential future security risk, not an attack that has taken place on the Bitcoin network. A public key is different from the private key used to spend Bitcoin. The risk stems from the possibility that a sufficiently powerful quantum computer could one day calculate a private key from a visible public key.
How does reusing addresses affect the risk?
Glassnode links address reuse to public key visibility for 25.8% of the Bitcoin supply. When spending from an address makes its public key visible on-chain, the Bitcoin left at that address or sent to it later may also be exposed.
According to Glassnode, moving Bitcoin to a new address whose public key has not yet been revealed on-chain can reduce this exposure. For Bitcoin held on an exchange, address management depends on the platform providing the custody service.
Not investment advice.