Blockstream CEO Adam Back said at Paris Blockchain Week that a coordinated future migration of Bitcoin to post‑quantum address formats could make it possible to identify how many coins tied to Satoshi Nakamoto remain actually accessible. His point: holders whose funds are vulnerable to a quantum attack would need to move them to newly designed post‑quantum addresses during a broadly publicized migration window. Any coins left unmoved after that window could reasonably be treated as effectively lost, he suggested. Back noted common estimates placing Satoshi’s stash between about 500,000 and 1 million BTC; blockchain analytics firm Arkham has estimated roughly 1.09 million BTC in Nakamoto‑linked wallets.
Concerns about dormant wallets and the quantum threat have already prompted policy ideas. This week, Jameson Lopp and five co‑authors published a Bitcoin Improvement Proposal intended to restrict future transfers from address formats that are exposed to quantum attacks, including older outputs whose public keys are already known on‑chain.
Back emphasized that developers and users have substantial time to prepare: a quantum advance capable of breaking Bitcoin signatures is likely decades away — he suggested a horizon on the order of at least 20 years — and present quantum hardware remains far from that capability, facing significant scaling and energy hurdles. That lead time, he argued, should permit careful design and coordination of a migration to a quantum‑resistant standard.
In December 2025, Blockstream Research proposed a hash‑based signature scheme as a promising post‑quantum replacement for Bitcoin’s current signature methods. The proposal relies on hash‑function security assumptions, aligning with Bitcoin’s existing reliance on hash primitives. For context, ECDSA depends on elliptic‑curve cryptography to verify signatures, while Schnorr signatures offer efficiency and privacy gains, for example by enabling signature aggregation; the suggested scheme aims to provide similar functionality while resisting quantum attacks.