Bitcoin BIP-360 & BIP-361: quantum-proof addresses and legacy freeze debate

Bitcoin developers have proposed BIP-360 (a first quantum-resistant address/output type) and are debating BIP-361, a plan to migrate—potentially “sunset”—legacy ECDSA/Schnorr spending paths that could become vulnerable if quantum computers reach a point where Shor’s algorithm breaks elliptic-curve signatures. For traders, the key takeaways are the threat model, the likely vulnerable supply, and the timeline uncertainty. The risk is about signature verification, not mining, because SHA-256 is expected to remain practically quantum-safe. The article cites estimates that roughly 6.5–6.9 million BTC (about one-third of supply) sit in addresses with exposed public keys, including around 1.7 million BTC in very early “ancient” P2PK outputs. Today, there is no active quantum break, and discussed migration windows span roughly 2029–2035. How the upgrades work: BIP-360 introduces a new address format (starting with “bc1r”) using post-quantum signatures such as NIST-aligned ML-DSA, designed to allow gradual migration in a soft-fork-like manner. The trade-off is larger signatures, which may increase block space usage and fees. BIP-361 focuses on enforcing a deadline: after “signature sunset,” old vulnerable spends would be rejected at the consensus layer. That raises an immutability vs. loss-of-access risk if coins cannot be migrated. Market relevance: this is precautionary infrastructure, not an immediate crisis. Still, BIP-361 headline risk can revive long-duration concerns around custody support, fee pressure, and governance-driven “freeze” narratives. Expect short-term volatility from headlines, with clearer direction only after concrete specs and test results emerge. (Primary keywords: BIP-361 and BIP-360)