The most consequential soft fork proposal in years
Bitcoin developers have formally published BIP-361, a three-phase plan to retire the signature schemes that protect roughly a third of all bitcoin in existence. If activated, any coin still sitting in a legacy address after the transition window would become permanently unspendable.
The proposal was circulated in draft form in February and has now been put forward for serious community review. Co-authored by Casa CTO Jameson Lopp and five other researchers, it is the first concrete, technically specified path toward a post-quantum Bitcoin. It is also the first proposal in Bitcoin's history that would, by design, freeze coins that fail to move.
What the three phases actually do
Phase A activates three years after the soft fork ships. From that point, nodes refuse to relay transactions that send funds to P2PK, P2PKH, and other address formats where the public key is, or can be, exposed. Existing holders can still spend from those addresses, but no one can send new coins to them.
Phase B is the part that has the community shouting. Five years after activation, nodes reject any spend that uses ECDSA or Schnorr signatures from a legacy script. In practice, that means any coin still sitting in a pre-Taproot address on that date becomes permanently unspendable on the main chain. The BIP authors estimate this covers approximately 6.7 million BTC, or roughly 34% of circulating supply. That includes the Patoshi-era coins attributed to Satoshi.
Phase C is the escape hatch, and the least finished part of the document. It sketches a future recovery path using zero-knowledge proofs: a legitimate holder could, in theory, prove ownership of frozen funds without revealing the private key and move them to a quantum-safe address. The authors explicitly note Phase C is still research-stage and may never ship.
Why the timing is not arbitrary
The practical question is not whether a cryptographically relevant quantum computer exists today. It does not. The question is the harvest-now-decrypt-later window. Anyone with enough storage can archive the Bitcoin blockchain and wait. Every public key that has ever signed a transaction is already out in the open. The day a working Shor-capable machine arrives, those coins are drained in a single block.
Lopp's argument, repeated across several posts this week, is that a Bitcoin network that waits for quantum to be obviously imminent has already lost. A soft fork needs years to coordinate, years more to activate, and years beyond that to migrate wallets. Starting the clock now buys the network a decade of runway. Starting in 2032 probably does not.
The objections are not technical
Critics of BIP-361 are not disputing the quantum threat. They are disputing the legitimacy of a protocol change that confiscates coins by inaction. Marty Bent, Mark Erhardt and others have pushed back hard on the framing, calling the five-year sunset confiscatory and inconsistent with Bitcoin's opt-in ethos. The counter-argument from the BIP authors is that the alternative is worse: a surprise quantum attack that drains Satoshi's coins, crashes confidence, and hands millions of BTC to whoever built the machine first.
There is no neutral option. Either the network moves coins that may never be moved by their owners, or it leaves them as a standing bounty for the first quantum attacker. BIP-361 chose the first.
What happens next
The proposal is still informational. It has a BIP number, a draft specification, and an author list. It does not have rough consensus, a reference implementation at Core level, or an activation path. The realistic timeline, even in a best-case scenario, is:
- 2026-2027: community debate, revisions, and a working implementation
- 2027-2028: activation via a speedy-trial or similar soft fork mechanism
- 2030-2031: Phase A takes effect
- 2032-2033: Phase B freezes legacy coins
That is a multi-year political process, and the community is visibly split. Expect the debate to get louder as soon as major mining pools and wallet vendors weigh in.
Bitcoin Gate Take
BIP-361 forces a conversation the network has been avoiding for a decade. You cannot simultaneously claim Bitcoin's rules are immutable and claim it will survive quantum computing without changing them. Something has to give, and the authors have chosen to surface the conflict now rather than in a crisis. Long-term holders should take two things from this: first, the coins you actually care about should not be sitting in a P2PK address from 2011, and second, the five-year window in the proposal is a floor, not a deadline. If you are holding Bitcoin for retirement, moving to a modern SegWit or Taproot address at your next opportunity is the right move regardless of whether BIP-361 ever activates.