Blockstream CEO Adam Back urged the Bitcoin development community to start building optional quantum-resistant solutions now, even though a practical quantum threat may be decades away. Speaking at Paris Blockchain Week, Back described today’s quantum systems as largely experimental and progressing slowly over the past 25 years, but he argued preparation is prudent. He favors optional upgrades that would let users migrate to quantum-safe cryptography if and when it becomes necessary.
The prospect that future quantum computers could break the cryptographic primitives that protect blockchain keys—and enable theft—has sparked industry debate. Back has previously placed the realistic threat horizon around 20 to 40 years and has emphasized that current machines are far from capable. Still, Blockstream maintains a dedicated quantum team to study potential attack vectors and has already trialed hash-based signatures on its Liquid layer-2 network as part of readiness work. Back also noted that Taproot’s design could support alternative signature schemes without forcing changes on existing users. “Preparation is key,” he said, arguing that controlled, optional changes are safer than scrambling to respond during a crisis.
Recent academic research from teams at Google and Caltech has suggested functional quantum hardware could arrive sooner than some expect and that less quantum power might be needed to threaten existing cryptography. Google warned such devices could enable rapid “on-spend” attacks against blockchains if they reach sufficient capability. When asked how developers would respond to an accelerated timeline, Back pointed to the community’s ability to act quickly under urgency, noting past instances where critical bugs were identified and patched within hours.
A separate technical proposal, BIP-361, authored by Jameson Lopp and five researchers, recommends a mechanism to freeze coins deemed quantum-vulnerable once quantum computers can realistically attack them; the proposal explicitly covers large dormant holdings attributed to Satoshi Nakamoto. The idea has been controversial. Critics in the Bitcoin community, including developer Mark Erhardt and commentator Phil Geiger, have called the approach authoritarian and likened it to confiscation, arguing it would amount to taking users’ funds to prevent theft.
The debate highlights a tension between proactive hardening and preserving bitcoin’s current design principles. Developers and companies continue to study quantum risks and potential mitigations while weighing practicality, user choice, and the community consensus process. Readers should verify developments independently as the discussion and research evolve.