Bitcoin developers propose freezing legacy coins after migration

A draft proposal formally assigned on Feb. 11, 2026 would freeze legacy Bitcoin addresses that fail to move to quantum-resistant formats within five years of a companion proposal’s activation. The draft, labeled BIP-361 and currently informational, lists six co-authors, including Casa CTO Jameson Lopp.

BIP-361 defines a three-phase soft-fork timeline that begins only after a companion quantum-resistant address proposal is activated. Phase A would start about three years after that activation and prevent wallets from sending funds to legacy address types. Phase B would follow two years later and render legacy signatures invalid at the consensus layer, leaving unmigrated coins permanently unspendable. A possible Phase C, still under study, would provide a limited recovery path using a zero-knowledge proof tied to a BIP-39 seed phrase.

The proposal cites the risk that a sufficiently powerful quantum computer running Shor’s algorithm could derive private keys from public keys already exposed onchain. As of March 1, 2026, more than 34% of all bitcoin are estimated to have exposed public keys, a set that includes early pay-to-public-key outputs created in Bitcoin’s first years. Those early outputs are estimated to contain about 1.1 million BTC.

Authors reference roadmaps and analysis that place a cryptographically relevant quantum computer as early as 2027 to 2030. The draft warns of a possible covert attack in which a quantum-capable actor could drain vulnerable addresses quietly, without immediate onchain alerts.

BIP-360, the proposal that would define quantum-resistant address types BIP-361 depends on, moved into testnet implementation through BTQ Technologies in early 2026. No activation of BIP-360 or BIP-361 has occurred.

The BIP-361 document frames the phase-out as a defensive measure: holders who migrate would not lose funds, while unmigrated coins could be taken by future attackers. The draft lists co-authors Christian Papathanasiou, Ian Smith, Joe Ross, Steve Vaile and Pierre-Luc Dallaire-Demers. In a March 2025 blog post, Jameson Lopp wrote that permanently burning vulnerable coins might be the least-worst option compared with allowing quantum actors to recover them and concentrate wealth.

The proposal has prompted criticism from parts of the Bitcoin community. A top comment on a forum read, “BTC ceases to be BTC if you fork it to mute wallets you think are a risk to your investment.” A post on the social platform X called the plan “highly authoritarian and confiscatory,” asserting upgrades should remain voluntary. One commenter summarized an objection: “We have to steal people’s money to prevent their money from being stolen.” An AI analysis of the X thread reported roughly 95% of top replies were negative.

Alternatives under discussion include rate-limited spending from vulnerable outputs and voluntary migration paired with supply burns. Developers also note that failure to reach consensus on a major rule change could risk a chain split. For now, BIP-361 is informational and requires no immediate action from bitcoin holders. Bitcoin Core and many developers have been cautious about rule changes that alter how existing outputs can be spent.