bitcoin has no "who signed this" field. @quipnetwork raised an uncomfortable question: if coins linked to satoshi suddenly moved, would we know whether the owner returned or a quantum attacker had recovered the key? the blockchain couldn't tell from the signature alone. early bitcoin outputs using pay-to-public-key scripts already expose public keys. if a future fault-tolerant quantum computer derived the corresponding private key, an unauthorized transaction could still satisfy bitcoin's existing signature rules. this isn't a present-day attack. current quantum hardware cannot do that. what interests me is the migration boundary. quip's post-quantum account approach adds another authorization layer for assets deliberately placed under its protection. but it cannot retroactively establish who legitimately controls untouched legacy coins. securing future transactions and proving historical ownership are fundamentally different problems. to me, that distinction deserves more attention than predictions about when quantum computers become powerful enough. a valid signature proves cryptographic authorization under the rules. it doesn't necessarily prove legitimate ownership.