In May 2026, Paradigm published a proposal for Provable Address-Control Timestamps (PACTs): a protocol that lets Bitcoin holders — including dormant wallets with exposed public keys vulnerable to future quantum decryption — timestamp cryptographic proof of key control using Bitcoin's own OP_RETURN outputs via OpenTimestamps. The commitment requires no on-chain transaction by the holder, reveals nothing about their identity or holdings, and produces a post-quantum-secure STARK proof that could be verified by a future protocol upgrade. This is a concrete instance of Bitcoin's timestamp server function being used to solve a problem its own security model may eventually create: proving that knowledge existed before the tools to derive it did.