PACTs let early Bitcoin holders timestamp key control

On May 1, Dan Robinson of Paradigm published a paper outlining “Provable Address‑Control Timestamps,” or PACTs. The proposal describes a way for Bitcoin holders to create a cryptographic proof that they control a private key, record a timestamp for that proof on Bitcoin today, and keep the proof private until it is needed.

Under PACTs, a user generates a proof tied to a private key and embeds a timestamp using Bitcoin’s existing transaction and block structure. The timestamped proof remains unused and unrevealed unless a future change to the network or a security threat makes it necessary to present proof of prior control. Robinson wrote that the approach would let Bitcoin holders “protect themselves” without publicly moving funds or signaling which addresses they control.

If Bitcoin later adopts rules that recognize such proofs, holders could present their stored proofs to regain access to funds whose original cryptography is no longer trusted. Verification could use cryptographic protocols that show control without revealing secret keys, according to the paper.

The PACT proposal is an alternative to a coordinated migration plan such as BIP-361. That proposal would move funds into quantum-resistant address formats over a transition period and eventually deprecate older address types. BIP-361’s recovery mechanisms rely on BIP-39 seed phrases introduced in 2013; wallets created before 2013 often lack those standardized seeds and would be harder to recover under a forced migration. PACTs do not depend on how a wallet was created; they rely only on proof of knowledge of the private key.

PACTs do not require protocol changes today and do not force public migration actions. That preserves privacy because holders do not need to transfer coins or announce control of addresses. The proofs have practical value only if the Bitcoin community later agrees to recognize them under revised rules, which would be a future consensus decision.

Current quantum hardware cannot break Bitcoin’s elliptic curve cryptography, and practical quantum threats are estimated to be years away. Researchers and developers note steady progress in quantum computing and point to high potential stakes if a sufficiently powerful quantum computer appears. Many addresses have already revealed public keys through past spending or address reuse, and some long-inactive early wallets that have never moved funds could be exposed if cryptography is later broken.

Bitcoin developers are debating when and how to respond. PACTs provide a method for individual holders to prepare now without changing the live protocol or forcing migrations. Other proposals prioritize early, enforced migration to quantum-resistant formats and include timelines and recovery mechanisms for newer wallets. The technical and governance choices will determine which addresses are covered and how privacy and user action are affected.