Bitcoin Split Over Plan to Freeze Quantum-Vulnerable Wallets

On April 14 a draft Bitcoin Improvement Proposal, BIP-361, proposed blocking new transactions to legacy addresses that expose public keys and are judged vulnerable to future quantum attacks. The document describes the effort as a post-quantum migration and legacy signature sunset and seeks to shift usage to quantum-resistant address types.

The proposal outlines two phases. In an initial phase the network would block new incoming transactions to address types deemed vulnerable. In a later phase the protocol would prevent spending from those legacy addresses after a multi-year grace period; drafters suggested a period of around five years. BIP-361 remains a draft and no timeline for signaling or adoption has been set.

Backers say the change would lower the risk that coins stolen by future quantum-capable machines could be quickly sold and cause sharp market moves. Jameson Lopp has been one of the most vocal supporters. Opponents say adding a mechanism that can freeze or block spending would undermine Bitcoin’s long-standing principle of users controlling their own funds. Adam Back is a prominent critic.

In a tweet on April 16, 2026, bitcoin developer and educator Jimmy Song wrote: ‘BIP-361 is a complete non-starter for me, but I would still like to see an attempt by its supporters to put it on the Bitcoin network as either a soft fork or a hard fork. Not because I want to get a fork dividend, but because we need to see how these things play out.’

Supporters cite estimates that about 6.7 million BTC are held in early address types that reveal public keys when spent. Early outputs using the pay-to-public-key (P2PK) standard expose a public key on the blockchain after a spend, which would make those outputs easier targets if quantum computers reach sufficient capability. The creator’s addresses are spread across more than 22,000 outputs, which would require an attacker to compromise many keys to move the full set of coins.

Technical disagreement centers on timing and feasibility. Supporters point to steady improvement in quantum algorithms and hardware and argue that early planning reduces long-term risk. Critics note that practical quantum machines capable of running the necessary algorithms at scale are not widely available and would be costly to build and operate today.

BIP-361 would place the responsibility on wallet users and custodians to migrate holdings to quantum-resistant address formats. Community alternatives discussed include a planned hard fork at a set block height with a long claim period and leaving legacy keys unchanged. The proposal has generated public debate but no network consensus; BIP-361 remains under review and no formal adoption process has begun.