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Provable Address-Control Timestamps (PACTs) are a new scheme proposed by Paradigm researcher Dan Robinson. In a post published May 1, 2026, Robinson outlined a method intended to help Bitcoin holders protect their assets from future quantum computing threats without moving funds on-chain.
PACTs allow holders to create a silent, off-chain commitment tied to their private keys. The holder generates a random salt and uses BIP-322 to sign a standardized message proving address control.
The signed message is then hashed into a commitment and timestamped using OpenTimestamps, a free and open-source service. Robinson said no Bitcoin transaction is required from the individual holder, because OpenTimestamps batches many commitments into a single transaction on the Bitcoin blockchain—making the cost of participation effectively zero for participants.
Robinson described the Bitcoin network as the foundation for the approach, noting that the Bitcoin whitepaper frames the network as a “distributed timestamp server,” a function that extends beyond recording transactions.
According to the proposal, the commitment reveals nothing about the holder’s address, public key, or wallet balance. Only an opaque hash is published. Robinson also emphasized that holders must securely store the salt, the BIP-322 proof, and the OpenTimestamps (OTS) file, since these elements would form the basis for any future rescue claim.
Robinson linked the need for PACTs to a “quantum sunset” scenario. He noted that Bitcoin addresses with exposed public keys are vulnerable to cryptographically relevant quantum computers (CRQCs), with the greatest risk for addresses that have previously sent transactions and therefore revealed their public keys.
Robinson estimated that Satoshi Nakamoto alone holds around 1.1 million BTC in such addresses, worth over $75 billion today.
In this framing, a quantum sunset would be a potential soft fork that freezes spending from quantum-vulnerable addresses. Robinson warned that without such a sunset, holders of vulnerable coins could be forced to move them or risk them being stolen. However, he also argued that a sunset creates a difficult trade-off for dormant holders: they would need to move coins publicly—revealing identity and activity—or risk losing access entirely.
Robinson said this would be especially consequential for an early holder such as Satoshi, who would effectively have to disclose that they are alive and still in possession of their keys.
PACTs are presented as a third path. Robinson’s proposal would let holders record ownership secretly now, then use a zero-knowledge proof later to claim coins under a rescue protocol, if one is adopted. The goal is to separate proving ownership from publicly moving funds.
Robinson described how a rescue process could work if Bitcoin adopted a sunset and a PACT-based rescue path. In that case, spending would require a STARK proof confirming the holder knew the private key before a defined cutoff date. The proof would also be bound to a specific rescue transaction to prevent replay attacks.
Robinson illustrated the concept with a hypothetical scenario in which Satoshi returns in 2040. He wrote that if Satoshi had used a cryptographic timestamping service in 2026, he could have timestamped a signature to establish that he knew the private key before CRQCs existed.
In the described approach, the salt and BIP-322 proof would not be revealed during a rescue claim. Only the cryptographic proof of prior key knowledge would be submitted to the network, maintaining privacy even through redemption.
Robinson also acknowledged limitations. He said multisig, complex scripts, custodial wallets, and hardware-wallet support would need careful standardization. He further noted there is no guarantee Bitcoin will adopt any rescue mechanism, and therefore holders should not treat PACTs as a substitute for migrating to quantum-safe addresses once those become available.
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