Coinbase’s Quantum Advisory Council has put a number on one of crypto’s most abstract fears. Between 6.9 and 7 million BTC, roughly a third of all Bitcoin that will ever exist, are sitting in addresses where corresponding public keys are already exposed on-chain. That means once quantum computers become powerful enough to crack existing cryptographic signatures, those coins are up for grabs.
The council’s report, published in June 2026 as a follow-up to an April position paper, draws a clear line between what’s safe and what isn’t. Bitcoin mining and hash functions? Quantum-resistant for the foreseeable future. Wallet-level digital signatures? That’s where the problem lives.
The 1.7 million BTC problem nobody controls
Within the broader pool of exposed coins, roughly 1.7 million BTC sit in legacy Pay-to-Public-Key addresses, the format used in Bitcoin’s earliest days. Many of these are tied to early mining activity or belong to wallets whose private keys have been permanently lost.
These coins can’t be migrated to quantum-safe formats because nobody is around to move them. And that creates a governance headache that goes well beyond cryptography.
