Bitcoin Developers Propose Freezing Quantum-Vulnerable Coins in New BIP-361 Plan

A group of Bitcoin developers has introduced a controversial proposal to address the growing threat of quantum computing to the network’s security. Casa CTO Jameson Lopp and five co-authors posted BIP-361 to Bitcoin’s GitHub this week, outlining a three-phase plan to migrate coins away from quantum-vulnerable addresses or have them frozen by the network itself.

The proposal, titled “Post Quantum Migration and Legacy Signature Sunset,” targets a significant vulnerability in Bitcoin’s design. About 34% of all Bitcoin sits in early Pay-to-Public-Key addresses with exposed public keys, a legacy format from Bitcoin’s earliest days. This includes an estimated 1.1 million BTC attributed to Satoshi Nakamoto, worth roughly $74 billion at current prices.

The core problem is straightforward but serious. Quantum computers running Shor’s algorithm could theoretically derive private keys from publicly exposed cryptographic keys. Google’s quantum research team has flagged 2029 as a possible threat date, creating urgency around potential solutions.

Here’s how BIP-361 would work in practice. Phase A would ban new transactions to legacy addresses three years after a related proposal called BIP-360 activates. Phase B would freeze all unmigrated coins two years after that. Phase C would offer optional recovery through zero-knowledge proofs using BIP-39 seed phrases, giving users a path to recover frozen funds.

The proposal represents the first concrete technical approach Bitcoin developers have put forward to address quantum risk. However, it immediately sparked debate within the community about whether such measures are necessary or even appropriate.

Lopp himself has called the proposal “a rough sketch” and said he doesn’t currently believe it’s necessary for adoption. He frames it more as a conversation starter than a finished solution. The Bitcoin developer community remains divided on whether the quantum threat justifies such aggressive action.

Critics argue that the freeze mechanism fundamentally violates Bitcoin’s core principles of permissionless and sovereign ownership. Freezing coins, even unmigrated ones, represents an unprecedented intervention in the network’s consensus rules. Bitcoin has never implemented forced transfers or asset freezes, and introducing such a mechanism could set a troubling precedent.

Others counter that inaction poses an existential risk to billions of dollars in Bitcoin holdings. They argue that a coordinated, planned migration is preferable to chaos if quantum computers suddenly make the existing signature scheme obsolete.

The timing of this proposal reflects broader institutional attention to quantum computing’s implications for blockchain security. While 2029 may seem distant, the infrastructure changes required to migrate Bitcoin’s security model would be enormous and require years of coordination.

Bitcoin has already implemented quantum-resistant address types. Users can voluntarily move coins to newer address formats that use different cryptographic assumptions not vulnerable to quantum attacks. BIP-361 would essentially make that voluntary migration mandatory through network consensus.

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The proposal also highlights Bitcoin’s ongoing challenge with legacy design decisions. Pay-to-Public-Key addresses were common in Bitcoin’s early years but are rarely used today. Most modern Bitcoin addresses don’t expose public keys on-chain, making them far less vulnerable to this particular quantum threat.

Lopp’s proposal will now enter Bitcoin’s standard review process. For any change to Bitcoin’s consensus rules to happen, it would require overwhelming support from miners, node operators, and the broader community. The bar for such changes is intentionally very high.

The debate over BIP-361 will likely continue as quantum computing advances and the 2029 timeline grows closer. Whether Bitcoin ultimately adopts this or another quantum-resistant approach remains uncertain, but developers are clearly beginning to take the threat seriously enough to propose concrete solutions.