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In brief Blockstream CEO Adam Back has proposed optional quantum-resistant upgrades for Bitcoin, challenging BIP-361’s mandatory coin freeze approach.
Google research shows quantum computers could break Bitcoin’s cryptography with 20-fold fewer physical qubits than previously thought.
An estimated 6.9 million BTC face quantum vulnerability, including Satoshi Nakamoto’s holdings.
Blockstream CEO Adam Back advocated for optional quantum-resistant Bitcoin upgrades at Paris Blockchain Week on Wednesday, a day after a group of Bitcoin developers pushed for a mandatory freeze on quantum-vulnerable Bitcoin.
“Preparation is key. Making changes in a controlled way is far safer than reacting in a crisis,” Back said at the conference. He also emphasized Bitcoin’s proven emergency coordination capabilities, noting that “bugs have been identified and fixed within hours. When something becomes urgent, it focuses attention and drives consensus.”
His approach contrasts with that of BIP-361, a proposal authored by Jameson Lopp and five other developers that would phase out quantum-vulnerable addresses over five years. The proposal, updated in Bitcoin’s official repository on April 15 under the title “Post Quantum Migration and Legacy Signature Sunset,” would implement a phased soft fork ultimately freezing coins that do not migrate—including the holdings of Bitcoin’s pseudonymous creator, Satoshi Nakamoto.
The intervention highlights a deepening split among Bitcoin developers around how to address the looming threat of “Q-Day”—the moment when a quantum computer with sufficient power to break the encryption used by Bitcoin emerges. Recent research from Google and Caltech suggests quantum computers capable of breaking the cryptocurrency’s security may arrive within years rather than decades.
The debate has been sharpened by accelerating progress in quantum computing. Google Quantum AI published research last month showing that quantum computers may break elliptic curve cryptography with fewer than 1,200 logical qubits. According to Google researchers, a superconducting qubit system would need fewer than 500,000 physical qubits to crack Bitcoin’s cryptography in minutes—a 20-fold reduction from previous estimates.
An estimated 6.9 million BTC face this vulnerability, including roughly 1.7 million in Satoshi-era mining rewards, the researchers noted.
Other stakeholders in the Bitcoin ecosystem are weighing in with different approaches to deal with the threat posed by quantum computing. Yesterday, BitMEX Research published an alternative approach to mitigate the impact of a “quantum related coin freeze,” advocating the creation of a “canary fund” of quantum-vulnerable coins, with a full freeze only implemented in the event of a spend from the fund address.
Other researchers have argued for a way to create quantum-resistant Bitcoin transactions without requiring a network fork, while outside the Bitcoin ecosystem other networks are exploring how to implement quantum resistance, including Ethereum, Solana, Naoris Protocol Circle’s Arc Network.