Quantum Attack Looms: Bitcoin's Vulnerable Supply at Risk of Permanent Loss
A proposal to protect Bitcoin from a potential quantum attack has been circulating among developers. If adopted, it would make around a third of all BTC permanently unspendable, including an estimated 1.7 million coins widely believed to belong to Bitcoin's anonymous creator, Satoshi Nakamoto.
The proposal is not a fringe idea and was authored by Jameson Lopp, a co-founder of the custody firm Casa, along with other security researchers. It has been assigned a formal number in Bitcoin's official proposal system and exists due to a credible threat that has moved from a theoretical concern to a scheduling problem over the past 18 months.
The proposed solution involves two steps: creating a new type of address that a quantum computer could not break (BIP-360), and setting a deadline for coins that have not migrated to the new address type to become unspendable (BIP-361). The critical detail is that BIP-361 cannot function until BIP-360 is activated first.
Currently, around 34 percent of all BTC had revealed a public key on the blockchain as of March 1, 2026, with approximately 6.7 million coins sitting in quantum-vulnerable addresses. This includes over 1.7 million coins from Bitcoin's oldest address format, which is widely believed to include Nakamoto's holdings.