Back estimates Nakamoto holds between 500,000 and 1 million Bitcoin.
Bitcoin News
Blockstream CEO Adam Back says a planned post-quantum migration of Bitcoin could finally reveal how many coins tied to Satoshi Nakamoto are still accessible. He made the remarks Thursday at ParisBlockchainWeek. Any holder wanting to protect vulnerable funds would need to move them to a new address format during such a migration.
Back estimates Nakamoto holds between 500,000 and 1 million Bitcoin. Blockchain data firm Arkham puts the figure at 1.09 million Bitcoin, currently worth around $81.6 billion. Back argued that coins left unmoved after a migration window closes could reasonably be treated as permanently lost.
His comments came one day after developer Jameson Lopp and five co-authors submitted BIP-361 to Bitcoin's official repository. The proposal, titled "Post Quantum Migration and Legacy Signature Sunset," would phase out quantum-vulnerable address formats over five years. Coins that fail to migrate, including Satoshi's holdings, would ultimately be frozen.
Back opposes mandatory freezes. He called for optional quantum-resistant upgrades instead, saying controlled preparation is safer than reacting to a crisis. He also pointed to Bitcoin's track record of rapid emergency coordination, noting that critical bugs have been patched within hours when the situation demanded it.
Back told the Paris audience that a quantum computer capable of breaking Bitcoin signatures is at least 20 years away. He described current quantum machines as less powerful than a $5 calculator. He acknowledged that energy consumption and other technical challenges grow more severe as these systems scale up.
In December 2025, Blockstream Research published a paper proposing hash-based signatures as a quantum-safe replacement for the ECDSA and Schnorr schemes Bitcoin currently uses. Security under that model would rest entirely on hash function assumptions, the same foundational layer already built into Bitcoin's architecture.
Google Quantum AI published research last month showing a superconducting qubit system would need fewer than 500,000 physical qubits to crack Bitcoin cryptography in minutes. That figure is 20 times lower than earlier estimates. Researchers put the total number of quantum-vulnerable Bitcoin at around 6.9 million, including approximately 1.7 million coins from the Satoshi era.
BitMEX Research has proposed a different path. It suggested creating a "canary fund" of quantum-vulnerable coins, with a full freeze only triggered if a spend is detected from that address. Other researchers have separately argued that quantum-resistant Bitcoin transactions could be achieved without requiring a network fork.
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