Coinbase report flags Bitcoin cold wallets exposed to quantum risks Between 6.9 and 7 million BTC sit in addresses where public keys are already visible on-chain, creating a ticking clock as quantum computing advances. 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. The vulnerability isn’t limited to ancient wallets, either. Address reuse in more modern transaction formats also contributes to the exposure. Every time a Bitcoin address is reused after spending, its public key becomes visible on the blockchain, widening the attack surface. Freeze them or lose them The council’s proposed solutions venture into politically radioactive territory for Bitcoin. Among the governance strategies outlined: setting migration deadlines that would require users to move their coins to post-quantum-safe addresses, and then freezing funds in vulnerable addresses that fail