Bitcoin quantum security: Adam Back opposes BIP-361 forced coin freezes

Bitcoin quantum security is back in focus after Blockstream CEO Adam Back said the community should prefer optional, opt-in quantum-resistant upgrades rather than protocol-enforced freezing under BIP-361. Speaking at Paris Blockchain Week, Back warned that “preparation is much safer than hasty responses,” arguing that waiting for a real-world quantum break is too risky. The dispute centers on BIP-361, “Post-Quantum Migration and Legacy Signature Sunset.” It outlines a phased approach: about 3 years after activation (Phase A) to stop new payments to legacy addresses, then roughly 5 years after activation (Phase B) to invalidate legacy ECDSA and Schnorr signatures. Under the plan, coins that do not migrate to quantum-resistant output types would be effectively frozen. The article cites estimates that around 1.7M BTC (about 34% of supply, including Satoshi-era holdings) remain in quantum-exposed address formats. Back rejects the freeze mechanism as a “red line” for decentralization and censorship resistance, calling it protocol-level expropriation even if framed as security. Traders should treat this as a governance-and-timeline headline risk for Bitcoin quantum security, not an immediate on-chain change. Sentiment may shift around long-term custody, migration expectations, and narratives about “forced changes,” increasing volatility tied to upgrade timelines.