Ledger CTO Disputes Claim That Only 30% of Bitcoin Faces Quantum Risk
About 30.2% of BTC has exposed public keys on-chain, but other copies may exist in devices, backups and transaction files.
Ledger CTO Charles Guillemet disputed the view that only about 30% of Bitcoin (BTC) faces quantum-computing risk, warning that public keys can exist outside the blockchain’s visible state.
About 30.2% of BTC has exposed its public key on-chain. The view that the remaining 70% is protected because its public keys have not been exposed is disputed, Guillemet said.
The on-chain figure does not capture every location where a public key may appear. Keys can also be present in extended public keys, devices, partially signed Bitcoin transactions, logs and backups.
A public key becomes public once a transaction is initiated, before the transaction is confirmed. As a result, exposure can increase when BTC moves, including when a previously unexposed public key is used in a transaction.
Guillemet said a hypothetical high-speed quantum computer could attack Bitcoin’s secp256k1 cryptographic system in about nine minutes. Such a machine does not currently exist.
That means keeping public keys hidden would not fully eliminate the long-term risk, Guillemet said. Bitcoin would eventually need to migrate to post-quantum cryptography, which is designed to withstand attacks from quantum computers.
