BIP-361, titled Post Quantum Migration and Legacy Signature Sunset, would push Bitcoin toward a long, staged break from legacy ECDSA and Schnorr signatures by making inaction increasingly costly for holders who leave funds in quantum-vulnerable outputs. Rather than offering explicit rewards for upgrading, the proposal tries to convert future cryptographic risk into a private financial incentive, betting that users will migrate once the cost of staying put becomes too high.
The logic is deliberately economic. The draft does not promise subsidies, fee rebates or protocol-funded compensation for moving coins into quantum-resistant outputs. Instead, it envisions a system in which legacy UTXOs become progressively harder to use, so that holders who fail to migrate could eventually find their bitcoin effectively stranded. In that framework, scarcity itself becomes the incentive, because any coins left behind would reduce the spendable supply and, proponents argue, increase the value of bitcoin that has already moved to safer rails.
A Slow-Motion Migration, Not a Sudden Break
BIP-361 is built as a phased transition rather than an immediate cutoff. After activation, the network would begin introducing rules that gradually tighten the usability of legacy outputs, with one scenario in the draft envisioning a ban on sending new bitcoin to legacy addresses three years later. The end goal is clear: the proposal is designed to make migration feel less optional over time, even if the process begins with what looks like a modest set of restrictions.
That structure builds directly on BIP-360, which introduced the pay-to-Merkle-root, or P2MR, output type as a candidate destination for funds moving into a post-quantum model. In practice, BIP-361 uses that earlier groundwork to shift the conversation from technical possibility to behavioral enforcement. The question is no longer only whether Bitcoin can support quantum-resistant outputs, but whether the network should deliberately pressure holders into using them before quantum capability becomes a live threat.
The draft frames the urgency in stark financial terms. It estimates that about 6.7 million BTC could be exposed to the transition, a figure it values at roughly $74,000 million. That is meant to show the scale of the problem, but it also reveals the proposal’s deeper strategy: if a meaningful portion of legacy coins becomes unspendable, the migration is supposed to reward compliant holders indirectly through tighter effective supply rather than through any direct on-chain payment.
The Real Fight Is About Control, Not Just Cryptography
That is precisely why the proposal has triggered strong resistance. Critics inside the Bitcoin community have described BIP-361 as “authoritarian and predatory,” arguing that it would give developers and upgraded nodes too much influence over the future usability of funds that were valid under previous rules. From that perspective, the proposal is not just a security measure but a direct challenge to long-standing assumptions about immutability, user control and the neutrality of the protocol.
Supporters see the issue differently. They argue that if credible projections place meaningful quantum risk as early as 2029, then waiting for a crisis would be reckless. In their view, the proposal is harsh because the threat is existential, and the point of staged friction is to force action before attackers can exploit exposed public keys at scale. Under that logic, Bitcoin’s social contract would be protected by changing its rules early rather than defending them unchanged into a new threat environment.
A staged sunset of legacy signatures would create demand for migration tooling, wallet upgrades, new custody workflows and clearer user communication. It would also introduce the possibility of stranded balances for firms or individuals slow to act, while potentially complicating leverage, collateral and derivative assumptions tied to current circulating supply. In that sense, the proposal turns a cryptographic debate into a balance-sheet and operations problem.
The deeper significance of BIP-361 is that it reframes post-quantum security as a market discipline rather than a protocol-funded transition. Holders would bear the cost of preparation, service providers would bear the burden of coordination, and anyone who ignored the timeline could end up paying for it through lost optionality. Whether Bitcoin eventually accepts that logic or rejects it in favor of a less coercive path, the proposal has already forced the network to confront an uncomfortable question: how much pressure is acceptable in the name of future-proofing the money itself.
