Blockstream CEO Adam Back said at Paris Blockchain Week that a future migration of Bitcoin to post-quantum address formats could reveal how many coins tied to Satoshi Nakamoto remain accessible. Owners wanting to protect holdings that are vulnerable to quantum attacks would need to move them to new addresses; coins left unmoved after a widely communicated migration window could reasonably be treated as lost, Back said. He noted estimates that Satoshi’s stash ranges from roughly 500,000 to 1 million BTC.
Concerns over dormant wallets and quantum risk have spurred proposals to limit movement of quantum‑vulnerable coins. On Wednesday, Jameson Lopp and five co‑authors published a Bitcoin Improvement Proposal aimed at restricting future transfers from address formats exposed to quantum attacks, including older coins whose public keys are already known. Blockchain analytics firm Arkham estimates Nakamoto-linked wallets hold about 1.09 million BTC.
Back argued developers and holders have a long runway to prepare: a quantum breakthrough capable of compromising Bitcoin signatures is likely decades away — he suggested at least 20 years — and current quantum machines are far from that capability and face scaling challenges such as energy use. That runway should allow design and coordination of a migration to a quantum-resistant standard.
In December 2025, Blockstream Research published a paper proposing a hash‑based signature scheme as a promising post‑quantum replacement for ECDSA and Schnorr signatures. The proposal would base security solely on hash function assumptions, consistent with Bitcoin’s existing use of hash primitives. For context, ECDSA uses elliptic‑curve cryptography to verify signatures, while Schnorr signatures improve privacy and efficiency by allowing signature aggregation.