The threat of quantum computing is causing some of Bitcoin’s most vocal developers to land in very different places.
Blockstream CEO Adam Back told Paris Blockchain Week attendees on Wednesday that Bitcoin developers should start creating optional quantum-resistant upgrades now, even though current quantum computers remain “essentially laboratory experiments” with progress that has been “incremental” in the 25 years he has followed the field.
“Preparation is key. Making changes in a controlled manner is much safer than reacting in a crisis,” said Blockstream CEO.
He highlighted his company’s work testing quantum-resistant transaction signatures on Liquid, a sister network to Bitcoin. He argued that a 2021 Bitcoin upgrade called Taproot was designed flexible enough to accept new signing methods without disrupting anyone currently using the network.
The comments echo Back’s position from last week, when he told CoinDesk that users should have about a decade to migrate their keys to quantum-resistant formats.
What’s different now is the context around them. BIP-361, the proposal from Jameson Lopp and five other developers released Tuesday, would phase out vulnerable quantum addresses over a fixed five-year schedule and freeze any coins that fail to migrate.
That includes about 1 million bitcoins attributed to Bitcoin’s pseudonymous creator Satoshi Nakamoto, and about 5.6 million coins Loppsays says haven’t moved in more than a decade.
Back’s framing reads as an implicit alternative to the forced migration of BIP-361. He did not directly mention Lopp’s proposal, but addressed the underlying question of whether the Bitcoin developer community can respond quickly to a sudden quantum breakthrough.
“Bugs were identified and fixed within hours. When something becomes urgent, it draws attention and generates consensus,” he said, suggesting that Bitcoin’s governance, by rough consensus, could handle an emergency without pre-programmed freezes years in advance.
The two positions represent the fundamental disagreement shaping the quantum debate over Bitcoin.
Back is betting that developers can coordinate quickly if the threat accelerates. Lopp is betting that this is not the case and that a scheduled freeze is the only way to avoid disorderly migration under pressure.
Google and Caltech researchers said last month that working quantum computers capable of breaking Bitcoin’s cryptography could arrive sooner than expected, moving the debate from the theoretical to the active stage.
