Key Takeaways
Coinbase's quantum advisory council is urging blockchain developers to begin post-quantum migration work now, warning that roughly 7 million Bitcoin sitting in exposed addresses could become the network's most contentious governance battle.
Coinbase's Independent Advisory Board on Quantum Computing and Blockchain released a report Thursday estimating that approximately 7 million Bitcoin — including about 5 million linked to reused addresses and coins believed to belong to Satoshi Nakamoto — are vulnerable to a future attack from a cryptographically relevant quantum computer. The council, which includes researchers from Stanford University, the University of Texas at Austin, the Ethereum Foundation, and Eigen Labs, said such a machine is more likely than not to exist as early as 2030.
"No quantum computer can break blockchain cryptography right now," the council wrote. "But timelines are uncertain, and the crypto community needs to start preparing now rather than debating exactly when the threat will arrive."
The report identified three options for coins that never migrate to quantum-safe addresses. The first is permanently freezing or burning them after a deadline. The second is doing nothing and letting holders decide. The third — which the council recommended as a middle ground — combines three mechanisms: an "hourglass protocol" that caps how much Bitcoin can move from vulnerable addresses per block, BIP-361 to phase out legacy signature schemes while allowing zero-knowledge proof-based relief for older wallets, and Provable Address Control Timestamps (PACTs) that let users pre-schedule future transfers before current signatures become invalid.
The governance question may prove harder than the technical one
Glassnode data cited in the report estimates that 6.04 million Bitcoin, or roughly 30 percent of issued supply, is already in an exposed-public-key state. The council stressed that introducing post-quantum signatures to the blockchain itself is a solvable technical problem. The harder question is what happens to coins whose owners never migrate.
"Forcing coins to be burned overrides property rights and sets a precedent for network-level interference that conflicts with Bitcoin's core principles," the council wrote, while also acknowledging that leaving vulnerable coins untouched risks an attacker using stolen funds to destabilize markets or finance malicious activity.
The debate is not hypothetical. Major blockchain networks have already begun preparing. The Ethereum Foundation formed a post-quantum security team in January and has explored replacing validator and wallet signatures with quantum-resistant alternatives. Vitalik Buterin mapped out a quantum upgrade roadmap in February. The Stellar Development Foundation unveiled a migration roadmap in April. Bitcoin developers continue to debate how vulnerable coins should be handled — and what happens to those that never move.
"The right time to prepare for a cryptographic transition is before it becomes urgent," a Coinbase Advisory Board spokesperson said. "Our view is that customer assets are safe today, but the industry should not confuse 'not imminent' with 'not important.'"
The council's report puts weight on a compromise combining phased retirement, transfer speed limits, and ownership proof mechanisms rather than choosing solely between burning and leaving assets untouched. But with an estimated 30 percent of Bitcoin supply already exposed and a credible quantum threat window of five to seven years, the window for reaching consensus is narrowing.
This article is for informational purposes only and does not constitute investment advice.
